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Approximately 50% of pollution of the Barcelona metropolitan area stems from motorised traffic.

Barcelona is the city with the highest density of vehicles per KM2 in Europe (1,079,523 vehicles/ day). It is also among the 5 most polluted cities in Europe, twice as much as Paris or London.

TMB is proposed as the main solution by offering a sustainable, quality public transport service.

TMB hence contributes to developing a sustainable model of city, with the following characteristics:

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Approximately 50% of pollution of the Barcelona metropolitan area stems from motorised traffic. Barcelona is the city with the highest density of vehicles per KM2 in Europe (1,079,523 vehicles/ day). It is also among the 5 most polluted cities in Europe, twice as much as Paris or London.

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http://www.urban-pathways.org/casablanca.html#:~:text=Transport%3A%20In%202005%20only%2015,GHG%20emissions%20from%20transport%20sector.

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You can download our complete Our World in Data CO ₂ and Greenhouse Gas Emissions database.

CO₂ and Greenhouse Gas Emissions Country Profiles

How are emissions changing in each country? Is your country making progress on reducing emissions? We built 207 country profiles which allow you to explore the statistics for every country in the world.

Each profile includes interactive visualizations, explanations of the presented metrics, and the details on the sources of the data.

See emissions in your country and how it compares to others:

Our 12 most visited country profiles

Every profile includes five sections

Why do greenhouse gas emissions matter?

Global average temperatures have increased by more than 1℃ since pre-industrial times

Human emissions of carbon dioxide and other greenhouse gases - are a primary driver of climate change - and present one of the world's most pressing challenges.¹ This link between global temperatures and greenhouse gas concentrations - especially CO ₂ - has been true throughout Earth's history.²

To set the scene, let's look at how the planet has warmed. In the chart, we see the global average temperature relative to the average of the period between 1961 and 1990.

The red line represents the average annual temperature trend through time, with upper and lower confidence intervals shown in light grey.

We see that over the last few decades, global temperatures have risen sharply - to approximately 0.7℃ higher than our 1961-1990 baseline. When extended back to 1850, we see that temperatures then were a further 0.4℃ colder than they were in our baseline. Overall, this would amount to an average temperature rise of 1.1℃.

Because there are small year-to-year fluctuations in temperature, the specific temperature increase depends on what year we assume to be 'pre-industrial' and the end year we're measuring from. But overall, this temperature rise is in the range of 1 to 1.2℃.³

Greenhouse gas emissions from human activities are the main driver of this warming

How much of the warming since 1850 can be attributed to human emissions? Almost all of it. The Intergovernmental Panel on Climate Change (IPCC) states clearly in its AR5 assessment report⁴:

"Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century. "

Aerosols have played a slight cooling role in global climate, and natural variability has played a very minor role. This article from the Carbon Brief, with interactive graphics showing the relative contributions of different forcings on the climate, explains this very well.

A changing climate has a range of potential ecological, physical, and health impacts, including extreme weather events (such as floods, droughts, storms, and heatwaves); sea-level rise; altered crop growth; and disrupted water systems. The most extensive source of analysis on the potential impacts of climatic change can be found in the 5th Intergovernmental Panel on Climate Change (IPCC) report.⁵

In some regions, warming has - and will continue to be - much greater than the global average

Local temperatures in 2019 relative to the average temperature in 1951-1980.⁶

When we think about the problem of global warming, a temperature rise of 1℃ can seem small and insignificant.

Not only is it true that 1℃ of rapid warming itself can have significant impacts on climate and natural systems, but also that this 1℃ figure masks the large variations in warming across the world.

In the map shown - taken from the Berkeley Earth global temperature report - we see the global distribution of temperature changes in 2019 relative to the period 1951 - 1980.⁷ This period from 1951 to 1980 is similar to the period global average time series shown in the section above.

There are a couple of key points that stand out.

Firstly, the global average temperature rise is usually given as the combined temperature change across both land and the sea surface. But it's important to note that land areas change temperature, both warming and cooling much more than oceanic areas.⁸ Overall, global average temperatures over land have increased around twice as much as the ocean. Compared to the 1951 - 1980 average, temperatures over land increased by 1.32 ± 0.04 °C. Whereas, the ocean surface temperature (excluding areas of sea ice) increased by only 0.59 ± 0.06 °C.

Since the Northern Hemisphere has more land mass, this also means that the change in average temperature north of the equator has been higher than in the south.

Secondly, from the map shown, we see that in some regions the temperature change has been much more extreme. At very high latitudes - especially near the Poles - warming has been upwards of 3°C, and in some cases exceeding 5°C. These are, unfortunately, often the regions that could experience the largest impacts such as sea ice, permafrost, and glacial melt.

Monitoring the average global temperature change is important, but we should also be aware of how differently this warming is distributed across the world. In some regions, warming is much more extreme.

How are greenhouse gas emissions and concentrations changing?

Atmospheric concentrations of CO₂ continue to rise

To slow down - with the eventual aim of halting - rising global temperatures, we need to stabilize concentrations of CO ₂ and other greenhouse gases in Earth's atmosphere.⁹ This link between global temperatures and greenhouse gas concentrations - especially CO ₂ - has been true throughout Earth's history.¹⁰ It's important to note that there is a 'lag' between atmospheric concentrations and final temperature rise - this means that when we do finally manage to stabilize atmospheric concentrations, temperatures will continue to slowly rise for years to decades.¹¹,¹²

But, far from stabilizing concentrations, greenhouse gases continue to accumulate.

In the chart here we see global average concentrations of CO ₂ in the atmosphere over the past 800,000 years. Over this period we see consistent fluctuations in CO ₂ concentrations; these periods of rising and falling CO ₂ coincide with the onset of ice ages (low CO ₂) and interglacials (high CO ₂).¹³ These periodic fluctuations are caused by changes in the Earth's orbit around the sun - called Milankovitch cycles.

Over this long period, atmospheric concentrations of CO ₂ did not exceed 300 parts per million (ppm). This changed with the Industrial Revolution and the rise of human emissions of CO ₂ from burning fossil fuels. We see a rapid rise in global CO ₂ concentrations over the past few centuries, and in recent decades in particular. For the first time in over 800,000 years, concentrations did not only rise above 300ppm but are now well over 400ppm.

It's not only the level of change CO ₂ in the atmosphere that matters, but also the rate that this has changed. Historical changes in CO2 concentrations tended to occur over centuries or even thousands of years. It took us a matter of decades to achieve even larger changes. This gives species, planetary systems, and ecosystems much less time to adapt.

Global emissions have not yet peaked

To stabilize (or even reduce) concentrations of CO ₂ in the atmosphere, the world needs to reach net-zero emissions. This requires large and fast reductions in emissions.

Are we making progress towards this? How far are we from this target?

At a time when global emissions need to be falling, they are in fact still rising, as the chart here shows. The world has not yet peaked.

Current climate policies will reduce emissions, but not quickly enough to reach international targets

Related charts

Current policies to reduce, or at least slow down growth, in CO ₂ and other greenhouse gas emissions will have some impact on reducing future warming.

As we see in the chart shown here, current implemented climate and energy policies would reduce warming relative to a world with no climate policies in place. This chart maps out future greenhouse gas emissions scenarios under a range of assumptions: if no climate policies were implemented; if current policies continued; if all countries achieved their current future pledges for emissions reductions; and necessary pathways which are compatible with limiting warming to 1.5 °C or 2 °C of warming this century.¹⁴

If countries achieved their current 'Pledges' (also shown on the chart), this would be an even further improvement. In this regard, the world is making some progress.

But if our aim is to limit warming to "well below 2°C" - as is laid out in the Paris Agreement - we are clearly far off track.

Robbie Andrew, a senior researcher at the Center for International Climate Research (CICERO), mapped out the global emissions reduction scenarios necessary to limit global average warming to 1.5°C and 2°C. Based on the IPCC's Special Report on 1.5°C and Michael Raupach's work, published in Nature Climate Change, these mitigation curves show that urgent and rapid reductions in emissions would be needed to achieve either target.¹⁵,¹⁶,¹⁷ And the longer we delay a peak in emissions, the more drastic these reductions would need to be.

We may be making slow progress relative to a world without any climate policies, but we are still far from the rates of progress we'd need to achieve international targets.

Which countries have set net-zero emissions targets?

Whilst current climate policies fall well short of what's needed to keep temperatures below 1.5 °C or 2 °C, countries have set more ambitious targets to reach net-zero emissions.

These interactive maps show the status of net-zero emissions targets across the world. This is based on the latest data from the Energy and Climate Intelligence Unit's Net Zero Scorecard.¹⁸

The target year to reach net zero varies by country - you can see the target year for each country by hovering over it on the map.

Note that the inclusion criteria may vary from country to country. For example, some countries may include international aviation and shipping in their net-zero commitment, while others do not. Or, some may allow for carbon offsets while others will not accept them. You can dig deeper into the specifics of each country's criteria here.

Can we make progress in reducing emissions?

Some countries reduced emissions whilst increasing GDP - even when we take into account outsourced production

There is a strong link between CO ₂ emissions, prosperity, and standards of living.

Therefore, if we're to ask the question: "Have any countries demonstrated that we can make progress in reducing emissions?", they would have to achieve both:

1. High standards of living;

2. Low levels of emissions, or at least large reductions in emissions to maintain that standard of living.

There are many countries that meet one criterion: rich countries that have high standards of living, but also high levels of emissions; and poor countries that have low levels of emissions but poor standards of living.

But, some countries have shown signs of progress. A number of countries have shown in recent years that it is possible to increase GDP whilst also reducing emissions. We see this in the chart which shows the change in GDP and annual CO ₂ emissions. Both production- and consumption-based CO ₂ emissions are shown - consumption-based emissions are corrected for traded goods and services, so we can see whether emissions reductions were only achieved by "offshoring" production to other countries.

A number of countries - such as the USA, UK, France, Spain, Italy, and many others - have managed to reduce emissions (even when we correct for trade) whilst increasing GDP.

The more important question is "Can we make progress fast enough?"

So we can see numerous examples of countries, with high standards of living, which have been successful in reducing emissions. This is a clear signal that it is possible to make progress.

But the key question here is probably less: "can we make progress?", but rather "can we make progress fast enough?".

As we explored earlier in this article, the world is currently far off-track from our 2 ° C target. If this is our definition of "fast enough" then we have little historical evidence to suggest that most, or even some, countries can reduce emissions (whilst maintaining high living standards) at the speed needed to achieve this.

We can make progress, but it's currently too slow. We need a large-scale acceleration of these efforts across the world.

How do we make progress in reducing emissions?

To make progress in reducing greenhouse gas emissions, there are two fundamental areas we need to focus on: energy (this encapsulates electricity, heat, transport, and industrial activities) and food and agriculture (which includes agriculture and land use change, since agriculture dominates global land use).

Below we've listed some of the key actions we need to make progress in each area. At a very basic level they can be summarised by two core concepts: improving efficiency (using less energy to produce a given output; and using less land, fertilizer, and other inputs for food production, and reducing food waste); and transitioning to low-carbon alternatives (in energy, this means shifting to renewables and nuclear; for food, this means substituting carbon-intensive products for those with a lower carbon footprint).

How can we decarbonize our energy systems?

1. Shift towards low-carbon electricity (reduce carbon intensity - carbon per unit energy)
- Renewables
- Nuclear energy
- Shift from coal to gas (which emits less CO₂ per unit of energy) as an interim step
→ Explore our work on energy.
→ Explore our data on CO2 emissions by fuel type.

2. Shift sectors such as transport, towards electricity. Some energy sectors are harder to decarbonize - for example, transport. We, therefore, need to shift these forms towards electricity where we have viable low-carbon technologies.
→ Explore our data on greenhouse gas emissions by sector.

3. Develop low-cost low-carbon energy and battery technologies. To do this quickly, and allow lower-income countries to avoid high-carbon development pathways, low-carbon energy needs to be cost-effective and the default choice.

4. Improve energy efficiency - energy per unit GDP.
→ Explore our data on energy intensity.

How can we reduce emissions from food production and agriculture?

1. Reduce meat and dairy consumption, especially in higher-income countries. Shift dietary patterns towards lower-carbon food products. This includes eating less meat and dairy generally but also substituting high-impact meats (e.g. beef and lamb) for chicken, fish, or eggs. Innovation in meat substitutes could also play a large role here.
→ Read our article on the carbon footprint of meat and dairy versus alternative foods.
→ Explore our work on meat and dairy production.

2. Promote lower-carbon meat and dairy production. We are not going to cut out meat and dairy products completely any time soon (and doing so is unnecessary - large reductions would be sufficient). This makes the promotion of lower-carbon production methods essential.
→ Read our article on the large differences in carbon footprint for specific meat and dairy products.

3. Improve crop yields. Sustainable intensification of agriculture allows us to grow more food on less land. This could help to prevent deforestation from agricultural expansion, and frees up land for replanting, or giving back to natural ecosystems.
→ Explore our work on crop yields.

4. Reduce food waste. Around one-third of food emissions come from food that is lost in supply chains or wasted by consumers. Improving harvesting techniques, refrigeration, transport, and packaging in supply chains; and reducing consumer waste can reduce emissions significantly.
→ Read our article on GHG emissions from food waste.

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Who is emitting greenhouse gases? Which countries and which sectors? And what needs to happen to reduce emissions?

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The number of annual public transport journeys is the number of annual boardings in public transport vehicles (all modes and all operators within the metropolitan area are concerned). Values are shown in journeys/million inhabitants.

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Get all the figures for Barcelona bus and metro management and activity

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More sustainable/safer transport in a post-COVID world

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More sustainable/safer transport in a post-COVID world

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April 23, 2020 By Ben Welle and Sergio Avelleda

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Safer, More Sustainable Transport in a Post-COVID-19 World

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The COVID-19 crisis has shown that effective public transport is vital to keeping cities running. Over the long term, public transport is one investment that can create jobs quickly while reducing carbon emissions, making roads safer and improving people’s access to their work and other opportunitie…

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Department of Land Management and Geographic Information Systems, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Prawochenskiego street 15, 10-720 Olsztyn, Poland

Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Prawochenskiego street 15, 10-720 Olsztyn, Poland

Author to whom correspondence should be addressed.

Received: 10 September 2020 / Revised: 27 September 2020 / Accepted: 30 September 2020 / Published: 8 October 2020

1. Introduction

Properly designed transportation systems should meet mobility and people requirements and also provide safety and eco-friendly vehicles [ 1]. According to the World Commission on Environment and Development, mankind should strive for sustainable development to meet the needs of the present without compromising the ability in order to meet the requirements of future generations [ 2, 3]. An important role in the sustainable development of space is played by the transport system. It plays a role in the sustainable development of space, because transport provides access to economic and social opportunities for all communities [ 4]. People living in the individual areas shall aim to develop sustainable transport systems, in particular road networks, which will enable them to achieve appropriate level of growth both in the economic, social and environmental spheres [ 5, 6]. However, we have to admit that it is the environmental aspect and the related need to overcome natural barriers that is one of the challenges we face when creating a transport network [ 7]. Moreover, Lithuanian researchers emphasize that modernization of transport infrastructure "should ensure sustainable mobility, communication of individuals and establish effective relations of business agents while providing support for the national economy" [ 8]. Transport (communication) accessibility is considered to be an important determinant of sustainable development for agglomerations and cities [ 9, 10, 11]. Not only clearly technical and surface aspects should be considered in the field of transport, economic conditions of the area; peoples' expectations and optimal solutions that would be environmentally friendly and would direct the transportation towards sustainability should be also taken into account. In the field of planning the most important feature is road safety, especially for cyclists and pedestrians. Safe infrastructure has to be provided for those types of transport and that means the physical separation of people from the road area and, if this is not possible, car speeds have to be reduced and education about road safety has to be provided from an early age. Urban planners who are taking care of transport have to have not only technical knowledge, but also, they need to demonstrate ingenuity and innovation. Moreover, the way the transport looks in a specific city also depends on the efficiency of local government units [ 12, 13]. This form of city planning practice can lead to sustainable transport.

On the other hand, the sustainability of transport in the cities is linked to high-quality implementation of innovative systems and to the need to gain public trust [ 14]. Planning of non-motorized transport depends on combining infrastructure improvement with education [ 15]. The perspective of the social dilemma sees the trend of continuous increase in the use and density of cars (more vehicles with fewer people covering longer distances on proportionally shorter roads) as a result of the unfortunate preference for short-term profits by car users at the expense of long-term losses to society [ 16]. A transport system can increase the efficiency and quality of life of a community if it is properly planned and managed, while at the same time the development stimulates transport demand [ 17]. Environmental protection requirements currently applied by companies promote improvements to already established systems [ 18].

The main goal of the article is to show the development of the transportation network in Vilnius and compare it with two chosen models (London and Copenhagen). Moreover, the authors would also like to analyze the studied city in relation to sustainable transport assumptions. The development of a transportation network is inevitably connected with the city's development [ 19]. Its growth means the same for a transportation system that can be implemented according to the highest standards. The transportation network can be also changed and modified in older parts of the city. This improvement should not only concern surface replacement but also a change in traffic, so it can be adjusted to peoples' needs [ 20]. The authors will indicate how it can be done in Vilnius.

2. Literature Review

Firstly, the idea of sustainable development [ 21] was focused on multi-annual problems [ 22] associated with environment and climate change [ 23]. The debate considering sustainable city development is today based on the idea of creating compact cities to provide them with balanced development [ 24]. In the case of passenger transport, social requirements are the main factors influencing sustainable transport indicators. [ 4]. On the other hand, Goldmana and Gorhamb [ 25] Goldmana and Gorhamb claim that, in order to be effective, a sustainable transport policy has to avoid the trap of the common transport policy of ignoring the larger systems in which transport activities are located.

A sustainable transport system mainly focuses on planning, politics and used technologies. Its main objective is to ensure efficient transit of goods and the high quality of transportation services. Besides, sustainable transport development is based on such city planning which would create urban areas free from cars and friendly for pedestrians and cyclists. Bike-sharing systems are getting more and more popular in large cities.17] as they are one of the most sustainable mean of transport in the urban area [ 20]. They are viewed as a cheap, efficient and healthy means of navigating dense urban environments [ 26]. Furthermore, transport in those cities should be based on public transportation means [ 27]. Professor David Banister, from the University of Oxford, has developed a paradigm, which presents sustainable transport rules that should be obtained in city planning [ 14]. Those principles are:

Technological innovation that would increase efficiency [ 14].

The first sustainable transport principle-reduced travel need-means that travelling has to be substituted by providing such technological solutions that could reduce these needs to a minimum. In this rule Banister notes the importance of the relationship between transportation and ICT (information and communicationstechnology), especially the growing importance of online shopping. The second sustainable transport principleimplies a strategy change ( Table 1) which means that car use levels should be reduced in favor of walking and cycling. An increasing number of communities in the United States are trying to improve the sustainability of their transport systems by shifting routine vehicle trips to walking and bike usage. [ 28]. Furthermore, Banister [ 14] proposes a new road hierarchy where pedestrians and cyclists are at the top of the sustainable transport pyramid, then in the middle there is public transport and car users at the bottom. This goal can be achieved by slowing down the city traffic and creating a separate area adjusted for public transport. Additionally, road payments should be also implemented (for example: paid entrance to the city centre and the old town). Moreover, the change of the roadway definition is also part of this principle that says the street is not only a car area. It should be perceived as a space with green modules which is also used by people (cyclists and pedestrians) and public transport means. This maxim encourages creative street use at different times of the day. For instance, during the weekend some roads can be transformed to street markets or can become fun zones. Those ideas encourage people to change their way of perceiving transport and they should be combined with a properly designed strategy for the best space use. The bicycle is a desirable form of transport, because it's environmentally friendly and economic in maintenence. Also, bikes have other positive effects: they are seen as a mean to stay healthy and in a good shape [ 29].

The third sustainable transport principle is about distance reduction. Its intention is to create mobility inside city districts that can lead to a shift in use of transportation modes for those that are environmentally friendly (vehicles), but also walking and cycling. Districts should be planned in a way that enables residents to use different services (housing, commerce, recreation, education) which can decrease the need to travel. It is recommended, in accordance with the principles of sustainable space development, to create "green urban islands" without car traffic, and to link them with each other to enable safe foot and bicycle traffic [ 30].

The fourth sustainability rule states that new technologies must be implemented which can make transport more efficient. Transport is responsible for 26% of global CO ₂ emissions and is one of the few industrial sectors where emissions continue to rise [ 31]. The role of technology is incredibly important and is inextricably linked to transportation, because it has a direct impact on its performance. The most sustainable solution would be if each transport mode would use the latest technologies, innovative engine construction, alternative fuels and renewable energy sources [ 32, 33, 34]. The priority in the glorious quest for sustainable is the development of green cities [ 35]. New solutions should also include reduction of noise generated by vehicles and ensure easy access to every part of the city in reasonable time. New vehicles should be environmentally friendly. Moreover, this principle is a combination of efficiency and drivers' behavior change towards more rational behavior; eco driving combined with following the traffic rules- especially the speed limits.

To sum up, the idea of sustainable transport is to keep the hierarchy of traffic participants. The most privileged group should be pedestrians, because they are the most defenseless and endangered group. The second group is cyclists, then the public transport network. The inclusion of bikes in a comprehensive planning framework seems to be a favourable approach which may lead to changes in urban transport [ 36]. At the very bottom of the classification are car users, because they are the most problematic community-it is they who often cause traffic jams and block the streets ( Figure 1).

Sustainable transport rules that are described above are the key to make the change in the way of thinking about spatial planning which is attractive for residents. Transport planning should involve people in creating and decision making processes so that they would understand occurring changes. It has to be remembered that social acceptation is a fundamental value to implement any reform successfully. GIS software can be used to achieve this goal.

3. Materials and Methods

Sustainable transport is seen as a global concept [ 37, 38, 39]. Its main idea is to strive for efficient communication which is economically advantageous and minimizes the harmful impact of vehicles on the environment. It focuses on both the control of harmful emissions and the promotion of sustainable means of transport such as public transport, bicycles or car sharing [ 40]. This type of transport and its paradigms assumes the reduction of the destruction of urban space due to the dominance of individual car transportation [ 41].

To reach these goals, the authors conducted their studies on many levels. At first, model cities with sustainable transport networks were presented. Then Vilnius the transportation system was analyzed, and finally the authors indicated sustainable transport solutions for this city.

While creating the proposed solutions for Vilnius, the authors used GIS tools that allow for transportation network modeling [ 42, 43]. Thanks to that it was possible to create maps that show how the existing transportation system can be transformed into a more sustainable form. The research covered the city of Vilnius, which is the capital of Lithuania. In Figure 2 the research area on the map of Europe is marked. ArcMap software was used to visualize the test results. The graphical algorithm [ 44] from the graphic theory was used to develop a model of optimal and decongested transport on a selected part of Vilnius City. The algorithmic solutions used to develop the graph concept were used to design new bicycle routes and stations. The authors used a set of combinations of new roads and stations in order to obtain an optimal combination that solves the problem of finding the shortest routes (Fleury Algorithm), the Chinese letter carrier (Dijkso Algorithm) and the salesman (Hamilton cycle) issue and also network reliability situation. Sustainable transport using graph theory algorithms has been used by many scientists [ 45, 46, 47, 48, 49, 50, 51, 52, 53].

4. Results and Discussion

4.1. Examples of Model Transport Networks

Public transport development: in Copenhagen the number of public transport modes was increased by 1200 bus stops, 40 train and S-train stations. Furthermore, there was also a new metro line built. Moreover, public transport means have priority over car users. That kind of approach gave the result of increasing by 8% the number of metro passengers between years 2008 and 2009. When the number of stops was increased, the number of passengers has grown as well [ 54].

Bicycle paths development-in Copenhagen the number of cycling tracks was increased to 350 km [ 55]. Additionally, the city has many cycling facilities such as green "waves"-which enables bike users to move around the town during rush hours without stopping-and green cycle routes which divide cyclists from infrastructure. Additionally, many intersections were redesigned to give priority to cyclists-stop lines for cars were moved 5 m behind. Furthermore, blue cycling routes were implemented in places with the biggest number of accidents to reduce the risk [ 56]. In London, thanks to creating a public transport and city bike network (Barclays Cycle Hire), the use of cars was limited. This result was also achieved by many social campaigns [ 57]. Sudden changes in horizontal and vertical geometry and cross-section are ominous for cyclists. Such risks can be minimised by safety audits or by using good design practice in the initial design phase [ 58].

Shared space-on Kensington High Street (London), although it is one of the busiest places (40,000 vehicles drive there daily), street signs, barriers for pedestrians and any other limits were removed. The central part of the area was used as parking for cyclists, which encouraged Kensington High Street users to move around freely. In Covent Garden, thanks to Seven Dials Monument Trust activity, which fought in the 1990s for restoration of one of the most characteristic monuments (Seven Dials), not only was the monument restored, but also a space not limited by any signs or regulations was created, although it is a very busy place. Traffic is slow here, and jams are seen rarely. What is more, for 16 years there have been no serious accidents [ 59].

Paid entry to the city center: in London the amount of greenhouse gases was reduced thanks to paid entry to the city center which discouraged car users. In turn, cheap public transport encourages people. Moreover, Prime Minister Boris Johnson's campaign, called Charge Point, encourages citizens to use electric cars, because there are free charging points in London. That action caused an increased number of sales and registered electric cars. The results from the Transportation Report for London 2013, presented in Figure 3, confirm the above creatures [ 57].

In many European cities support for public transport and cycling in daily mobility is considered to be an effective way to reduce air pollution, traffic jams and carbon dioxide emissions [ 60]. Planning and transport experts encourage various sustainable transport alternatives, such as using public transport, walking and cycling as affordable transport options to counteract the negative effects of car use for all [ 61]. The development of more sustainable transport requires the adequate establishment of four pillars: efficient land-use and transport management; fair, efficient and sustainable financing; strategic infrastructure investment; and attention to neighbourhood design [ 62]. Urban planning can create more efficient and environmentally friendly municipal freight transport systems. The use of innovative ICT (information and communication technologies) and ITS (intelligent transport systems), a change in the mentality of logistics managers and public-private partnerships can promote urban logistics policy measures [ 63]. Worldwide, several cities are striving for more sustainable urban transport systems in order to reduce accidents, congestion, air and noise pollution, and to improve social interaction, the ability to live and the value of amenities [ 64].

Figure 4 and Figure 5 show the benefits from the solutions used in Copenhagen. Growth in the number of people cycling to work or educational institutions and feeling safe in traffic can be observed.

Thanks to an efficient network of public transport and cycling routes in Copenhagen, car use has decreased so much that in 2010 up to 47% of citizens did not own car and 58% rode their bike to work or school on a daily basis [ 65].

4.2. Transport in Vilnius

Can sustainable transport be found in Vilnius? Peripheral regions in post-socialist countries appear to be particularly underinvested in terms of their transport, including at the local and regional level [ 7]. The authors focused on analyzing Vilnius for use of sustainable transport principles. Both already taken actions and problematic areas were analyzed. Additionally, new solutions were proposed, because efficiency of the transportation system is extremely important due to the growing scale of demands concerning mobility. Primarily, it has to be said that the main problem in Vilnius, from which difficulties in the transport department result, is the urban sprawl (uncontrolled growth of urban areas) that is inconsistent with a compact cities strategy promoted by the EU [ 66, 67]. An attempt to show places (areas) with problematic transportation zones was taken by the scientists from Vilnius Gediminas Technical University. By using GIS tools they have managed to elaborate a model, which divides the city into 51 TAZ (traffic analysis zones) and specifies their efficiency [ 68]. During creation of this model, accessibility from the city center to different zones, population density and the number of jobs in the zones, density of public communication network and the number of daily trips in each zone were taken into consideration. To perform the necessary calculations, scientists used a modified Bogart and Ferry model [ 69].

The research results carried out by Jakimavičius and Burinskienė [ 68] in search of sustainable communication in Vilnius show that there are efficient communication zones, but there are only two of them: Santariškės and ŽemiejiPaneriai. In contrast, zones like Centras I, Centras II, Lazdynai, Karoliniškės, Antakalnis, Senamiestis, Šnipiškės and Naujamiestis were considered as zones having serious problems such as a lack of parking space and constant traffic jams. Abnormalities were also identified in Verkiai, Dvarčionys, Valakupiai, A. Paneriai and Tarandė zones. Moreover, sustainable transport principles about reducing the number of cars and promoting walking and cycling along with using public transport means are not completely implemented in Vilnius. Jakimavičius and Burinskienė [ 70] in one of their articles proposed a scenario saying that despite a growing number of cars in Vilnius, it would be possible to introduce a certain degree of sustainable transport rules if cars would be more efficient and use alternative energy sources. However, as they admit themselves, that kind of scenario is hard to accomplish. At Lithuanian motorway intersections, various traffic and safety engineering solutions are applied intensively [ 71]. On the other hand Klibavičius and Paliulis [ 72] demonstrated that the number of vehicles is similar to the statistical distribution of the data defined as such: the arrival of different vehicles at roundabouts is close to Poisson distribution.

Transport indicators for Vilnius in Figure 6 show a comparison between 1995 and 2005. It can be observed that despite an average of public transport passenger growth of 3.7% a year, there are still 17% fewer people using this type of transportation than in 1995. Nevertheless, there is in total more trips made by pedestrians, bicycles and public transport than those made by car ( Table 2).

The number of people owning a car in Vilnius has been increasing by 3% per year since the 1990s. The reason for this situation could be the improving economic situation in the country. However, it should be noted that there are less people that use cars than those who choose public transport; in turn, this group is smaller than people travelling on foot and cycling (35.1% of city dwellers in 2005).

Unfortunately, forecasts for 2025 predict a growing trend in car and fuel use [ 68]. That is why measures to improve the communication network have to be taken in Vilnius to help the city in endeavoring to establish sustainable transport rules.

4.3. Sustainable Transport Solutions for Vilnius

Metro lines construction: Vilnius is supported by 456 km of trolleybus lines that carry 400,000 passengers per day. Besides that, citizens use buses which carry 300,000 passengers daily. This means that 33.9% of people from urban and suburban areas, consisting of 900,000 residents (540,000 living in Vilnius), use public transport. However, because of the overload in the city center, average speed in this area is about 20 km/h, which successfully scares people away from using public transport [ 68]. That is why the city government decided to study the usefulness of new means of transport, including a metro ( Figure 7). Research conducted in the years 2006-2008 shows that 57% of responders opted for creating a metro while only 20% of them supported tram building. For the metro case, an organization called Vilnius Metro was created. The association is active in informing people about new solutions and held negotiations with investors so that a metro could be built from private resources [ 73].

After the analysis of model solutions in selected cities and presenting the sustainable transport assumptions, the authors introduce possible solutions thanks to which transport in Vilnius can be treated as sustainable.

The map below presents a possible solution for the expansion of a bicycle network in a selected location in Vilnius. It is a neighborhood with a large transportation route, residential buildings and a park/forest. The possibility of linking the places where housing is located with the traffic routes will allow residents to easily change from bicycle to bus. Designation of bicycle paths and places from which bicycles can be rented in recreational areas should encourage the use of green spaces.

What is important in the proposed solution ( Figure 8) is that it combines walking, cycling and public transport. The use of public transport is often uncomfortable due to the long distance to the stop. The connection between the stop and the place from which people can rent a bicycle can encourage them to use public transport. Parking in cities is associated with looking for a place and parking fees. That is why choosing public transport or bicycles relieves the traveler from looking for a place to leave the car. Some bike sharing systems reward their users if they leave the bike at the station. This saves them a fee for using a bicycle. Therefore, it is necessary to make bicycle stations available in attended places, as well as in places close to the living areas.

As shown in the maps above, changes can be made to the existing transport system, thanks to which it can be said that the transport in Vilnius would be sustainable. In presenting these proposals, the rules of sustainable transport contained in the Pyramid of Sustainable Transport ( Figure 1) were respected. Finding the optimal solution for the Fleury, Dijkso, Hamilton cycle algorithm while maintaining apex and edge consistency required the development of many variants and testing them in order to achieve a system where algorithms have solutions. In this way, we minimized costs and maximized functionality and usability. The limitations include natural and cost barriers. We can assume that we are looking for the cheapest possible network with a predetermined reliability, or we are looking for a network with a fixed cost and the highest possible reliability. Of course, the more lines (edges), the greater the reliability. On the other hand, however, building any connection costs money. Additionally, it is assumed that the solution you are looking for has an Euler cycle, which means that there is a road that starts and ends at the same point and requires you to walk on each street exactly once. The graph is a full graph, which means it has at least one Hamilton cycle. Since the graph has a finite number of vertices, there is one (not necessarily the only one) in the set of Hamilton cycles that has a minimum sum of edge weights. We start from any vertex. Each successive edge we pass on is selected from the edges coming from the vertex we are currently in. If it is possible, removing the selected edge should not cut the graph into two "pieces". If we manage to reach the vertex from which we started and go through all the edges, the resulting path is an Euler cycle. The problem of finding Hamilton's cycle is similar to the problem of the combo-chainer being "difficult" due to the longtime of known algorithms. If the Hamilton cycle does not exist in the tested graph, then in that case we may even have to check all possible permutations of the vertex set to make sure that such a cycle does not exist. We want to design a network with the required reliability, the cost of which will be as low as possible. So, we are looking for a graph with n vertices and as few edges as possible, whose vertex consistency or edge consistency is k.

5. Conclusions

In Hamilton-Baillie's opinion, a different and better solution is creating shared and integrated spaces that bind different forms of transport in one piece [ 59]. This means the removal of signs, lanes, traffic lights, etc. and letting people spontaneously shape the traffic rules. However, it has to be remembered that this kind of solution may be achieved only by cooperation of people and local government combined with an approach change. There is a common opinion that residents of the suburbs are bound to use individual forms of transportation, and public transport does not meet their needs [ 74].

To sum up, Vilnius is a place where two city models (compact and traditional urban sprawl model) collide. This is because Vilnius is developing both in terms of sustainable transport (Santariškės and Žemieji Paneriai zones), but there are also zones like Centras I, Centras II, Lazdynai, Karoliniškės, Antakalnis, Senamiestis, Šnipiškės and Naujamiestis that have serious problems with traffic.

However, change in city transportation characteristics towards more sustainability, like in the Banister paradigm, is a long process. Both the model and infrastructure for traditional transport systems were developed many years ago. That is why the whole infrastructure and land use planning in Vilnius require gradual changes. Moreover, the starting point for every city should be different, because it depends on individual factors such as the political situation, local conditions and available funds. This is the reason why Vilnius has to work on its own solutions (based on those already existing and functioning efficiently in the world, e.g., Copenhagen and London) leading towards sustainable transport.

Author Contributions

Conceptualization, M.O. and D.A.-K.; methodology, M.O. and D.A.-K.; software, M.O.; validation, M.O.; formal analysis, A.K.; investigation, M.O. and D.A.-K.; data curation, M.O.; writing-original draft preparation, M.O. and D.A.-K., writing-review and editing, M.O. and A.K.; visualization, M.O.; supervision, M.O.; project administration, M.O. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

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The Coventional Approach
(Transport Planning and Engineering)

An Alternative Approach
(Sustainable Mobility)

Physical dimensions

Social dimensions

Mobility

Accessibility

Traffic focus, particularly on the car

People focus, either in (or on) a vehicle or on foot

Large in scale

Local in scale

Street as a road

Street as a space

Motorized transport

All modes of transport often in a hierarchy with pedestrians and cyclists at the top and car users at the bottom

Forecasting traffic

Visioning on cities

Modeling approaches

Scenario development and modeling

Economic evaluation

Multicriteria analysis to take account of environmental and social concerns

Travel as a derived demand

Travel as a values activity as well as a derived demand

Demand based

Management based

Speeding up traffic

Slowing movement down

Travel time minimization

Reasonable travel times and travel time reliability

Segregation of people and traffic

Integration of people and traffic

Indicator

1999

2005

Street network density (km/km ²)

1.9

2.4

Public transport density (km/km ²)

0.55

0.62

Bicycle paths networks density (km/km ²)

0.10

0.16

# data[].attributes.attachment_link.title
Sustainable Transport: An Efficient Transportation Network-Case Study

# data[].attributes.attachment_link.description
The article describes sustainable transport principles and guides that can lead cities towards a more efficient transportation network. The authors also show good practice used in different urban areas, such as London and Copenhagen. Furthermore, Vilnius was analyzed for its sustainable transport rules and mobility.

# data[].attributes.attachment_link.readable_text
Department of Political Science, Roma Tre University, Via Gabriello Chiabrera 199, 00145 Rome, Italy

Department of Logistics, Molde University College, PO.Box 2110, 6402 Molde, Norway

Department of Engineering, Roma Tre University, Via Vito Volterra 62, 00146 Rome, Italy

Author to whom correspondence should be addressed.

Received: 4 December 2018 / Revised: 20 December 2018 / Accepted: 21 December 2018 / Published: 28 December 2018

This paper aims at understanding and evaluating the environmental and economic impacts of a crowdshipping platform in urban areas. The investigation refers to the city of Rome and considers an environmental-friendly crowdshipping based on the use of the mass transit network of the city, where customers/crowdshippers pick-up/drop-off goods in automated parcel lockers located either inside the transit stations or in their surroundings. Crowdshippers are passengers that would use the transit network anyhow for other activities (e.g., home-to-work), thus avoiding additional trips. The study requires firstly, estimating the willingness to buy a crowdshipping service like the one proposed here, in order to quantify the potential demand. The estimation is realized adopting an extensive stated preference survey and discrete choice modeling. Then, several scenarios with different features of the service are proposed and evaluated up to 2025 in terms of both externalities (local and global pollutant emissions, noise emissions and accidents reductions) and revenues. The results are useful to understand and quantify the potential of this strategy for last mile B2C deliveries. Moreover, it provides local policy-makers and freight companies with a good knowledge base for the future development of a platform for public transport-based crowdshipping and for estimating the likely impact the system could have both from an economic and environmental point of view.

1. Introduction

Urbanization and e-commerce are two fast-rising trends that make city logistics solutions even more challenging. The European Commission has started promoting research and innovation to define effective policy interventions in urban freight transport [ 1]. Several urban freight transport strategies could be adopted to find a good balance between positive impacts on accessibility and economic development and negative externalities in terms of congestion and polluting emissions (e.g., [ 2, 3]). Recent and relevant solutions refer to: Demand management (e.g., [ 4, 5]); electrification (e.g., [ 6, 7]), regulatory measures (e.g., [ 8, 9]) and improved capacity utilization (e.g., [ 10, 11]).

Crowdshipping is one of the most promising solutions that foresees an integration of passenger and freight mobility. In line with the sharing economy, it implies delivering goods using the crowd making use of modern information communication technologies [ 12].

The type of crowdshipping this paper investigates is linked to e-commerce in its B2C manifestation and is based on crowdshippers using public transportation, specifically using the metro network of a city. In fact, planning urban freight activities along metro lines is relevant for sustainable logistics [ 13]. Crowdshippers are, in this case, passengers that would use the metro lines anyhow for other motivations (e.g., home-to-work) and they pick-up/drop-off goods in automated parcel lockers (APLs) located either inside the metro stations or in their surroundings.

The adoption of APLs demonstrated an increase in the number of successful first-time deliveries, to optimize delivery rounds and to lower operational costs in the e-commerce B2C sector [ 14]. In this study, the potential of APLs are connected with the metro network, thus proposing a more environmentally friendly crowdshipping with respect to a fully based rubber-tired crowdshipping. In fact, it does not imply performing any additional trips in the last mile delivery, and those that are taking place are making use of one of the least polluting modes.

This paper aims at understanding and evaluating the environmental and economic impacts of this public transport-based crowdshipping in urban areas. In fact, it is expected that this goods distribution system would produce a positive impact on the environment and on the urban community by exploiting unused transit capacity. On the other hand, the paper aims to assess also the economic sustainability of the service.

The evaluation focuses on the last mile of the delivery chain in the urban area of Rome. The last leg of delivery is also the most appropriate part of the e-commerce supply chain where a crowdshipping scheme might prove applicable and useful [ 15, 16, 17]. In fact, most of the goods are small in size and light in weight, allowing the 'crowd' of commuters to act as a last-mile vector. Investigating crowdshipping in Rome is also motivated by its characteristics: Large extension, complex transit network and congested road network. In more detail, almost three million people live in the city, who perform around 700,000 thousand trips during the morning peak period; congestion causes about 135 million hours lost, while operators perform more than 35,000 loading/unloading operations [ 18, 19].

This paper is structured as follows: Section 2 reports the background of crowdshipping, underlining the need to forecast the economic and environmental sustainability of this growing sharing system; Section 3 describes the methodological approach used to assess economic and environmental sustainability; while Section 4 reports the results obtained related to the implementation of the public transport-based crowdshipping service in Rome. Section 5 concludes illustrating future research.

2. Background

This research builds on previous studies by explicitly addressing both environmental and economic benefits of an innovative crowdshipping system, focusing on emissions and traffic externalities. Moreover, it contributes to the increasing body of the literature on public transport-based crowdshipping services. In fact, to the best of our knowledge, only a few studies have dealt with this kind of crowdshipping system [ 20, 21, 22], whereas most of the literature on this issue focuses on car-based crowdshipping.

Buldeo et al. [ 23] performed a literature review on the state of practice of crowdshipping identifying three main issues affecting its overall sustainability: (i) The involvement of professional third parties in case of insufficient or underperforming crowd; (ii) crowd motivation (either monetary or environmental/social); (iii) modal choice (car vs soft modes, public transportation, or clean vehicles).

Some researches have focused on environmental impacts. Buldeo et al. [ 24] compared the external costs imposed on society when delivering parcels with crowdshipping and professional systems, finding that uncontrolled use of the platform (car-trips dedicated to delivering parcels) results in higher external transport costs and thus higher emissions. Therefore, crowd logistics could offer a sustainable alternative only if the crowd exploits existing car trips. Savelsbergh and Van Woensel [ 25] discuss the case of Walmart that foresees the involvement of its in-store customers delivering items ordered by online customers, conclude that, from a city logistics perspective, this type of service would increase the number of freight movements and make coordination and consolidation of direct-to-consumer deliveries even more challenging.

Other researchers have focused on the economic and financial aspects. Mak [ 26] investigated the potential impact on retailers' operational and marketing strategies due to the use of in-store customers delivering orders to online customers. Archetti et al. [ 27] used a multi-start heuristic procedure for vehicle routing problems with occasional drivers, showing that employing occasional drivers may reduce the costs for satisfying the demand, especially if coupled with an appropriate compensation scheme. Gdowska et al. [ 28] introduced an agent-oriented approach to minimize problems in the last-mile delivery for couriers who occasionally "carpool" a parcel. They provide a method to calculate the total delivery cost associated with both the occasional couriers' compensation fee and the delivery cost generated by the professional delivery fleet used for the delivery of remaining parcels. Their stochastic approach assumes that the occasional carpooler is an independent agent, who is free to reject assignments. Behrend and Meisel [ 29] analyze a platform combining shipping requests with community members' planned trips through the development of mathematical and heuristic models with the aim of maximizing profits. The results quantify the benefit of integrating item-sharing (i.e., sharing of tools or leisure equipment between community's members) and crowdshipping as a function of crowdshippers' detour flexibility and compensations. Due to these findings, the authors conclude that integration of item-sharing and crowdshipping has the potential to push collaborative consumption by delivering through the crowd.

The increased attention in urban freight behavior analysis (e.g., [ 30, 31]) has led academic researchers investigating stakeholders' preferences and attitudes. Marcucci et al. [ 32] explore the necessary pre-requisites a crowdshipping service needs to satisfy and to be attractive within the highly competitive urban freight delivery market. They find that students are prone to operate as crowdshippers deviating from the usual path, but this willingness depends on the remuneration and delivery box dimensions. At the same time, online buyers are willing to receive goods via a crowdshipping service especially when they can contact the crowdshipper and track the package. Punel and Stathopoulos [ 33] used state choice experiments, investigating the factors influencing the users' acceptability towards hypothetical delivery schemes performed by professional and non-professional shippers. Punel et al. [ 34] compare attitudes, preferences, and characteristics of crowdshipping users and non-users. They found that young people, men, and full-time employees and individuals with a strong sense of community and environmental concern were more likely to use crowdshipping service. Yildiz and Savelsbergh [ 35] deal with crowd-sourced transportation for on-demand meal delivery, investigating the interaction between courier satisfaction (i.e., couriers' willingness-to-wait), courier compliance (i.e., couriers' offer acceptance-probability) and profit.

Finally, other studies describe crowdshipping initiatives illustrating their operational/technological functioning (e.g., [ 36, 37]).

3. Materials and Methods

This section illustrates data, methods, and models adopted in this study to evaluate the environmental and economic impacts of a public transport-based crowdshipping platform.

The methodology architecture is reported in Figure 1. The first step is to define possible crowdshipping demand levels as a function of the main features of the service. Second, the demand is converted into orders, and the vehicle-kilometers saved by public transport-based crowdshipping are computed. Finally, the benefits and costs of the service are evaluated in terms of externalities reductions, revenues, investment, and management costs, thus computing the net present value of the proposed service.

This paper uses stated preference (SP) exercises, including the most important features associated with the willingness to use the crowdshipping service, to estimate the crowdshipping demand. SP was chosen since it is perfectly suitable for investigating individuals' perceptions, acceptance, and reactions towards hypothetical conditions not present in the market. In fact, SP has been widely used in the transportation context for: (i) Evaluating potential behaviour changes (e.g., [ 38, 39]); (ii) estimating modal shift (e.g., [ 40, 41]); and (iii) analysing attitudes or satisfaction related to innovative services (e.g., [ 42, 43]). SP has also been applied to the freight sector for: (i) Predicting stakeholders' reactions to policy changes (e.g., [ 44, 45]); (ii) fostering stakeholder involvement and acceptability in the planning process (e.g., [ 46, 47]), and (iii) in combination with other methods such as agent-based models (e.g., [ 48, 49]). Following Gatta and Marcucci [ 50] who suggest using advanced experimental design techniques when performing SP exercises in the urban freight transport field, a Bayesian D-optimal design was adopted to define the choice tasks in the questionnaire. The final configuration foresees four different blocks, each including three choice exercises with three alternatives (two unlabeled linked to a crowdshipping service) and a "no choice" option (i.e., the status quo of not using the crowdshipping service).

Specifically, the SP studies the role of service time and cost, parcel tracking availability, delivery schedule date/time flexibility ( Table 1) in stimulating potential e-commerce users to choose a crowdshipping service for delivering the goods they have bought. Shipping fees and time refer to current national shipping companies operating in Italy. Additional data was collected (e.g., socio-demographic characteristics, actual behavior and attitudes).

The SP survey was undertaken during October 2017 from approximately 240 inhabitants of the city of Rome. Almost two-thirds of the interviewees were contacted via social media (i.e., Facebook) and e-mail, while one third were "face-to-face". Respondents had to fill in the same web-questionnaire. We used the time duration for completing the questionnaire as a proxy for reliability, verifying no significant difference between the different methods.

Next, discrete choice modeling was used to analyze SP data. A multinomial logit model was estimated to calculate the probability of choosing a crowdshipping service. The estimation process was based on a likelihood maximization and performed via BIOGEME [ 51].

Scenario analyses were performed from the econometric results and different assumed service specifications. In particular, three demand scenarios (base, favorable, and unfavorable) were considered depending on the acceptability level of the service.

Individual orders were transformed into vehicle equivalent units, i.e., the number of commercial vehicles needed to transport a certain quantity of orders, so to compute the vehicle-kilometers savings (shifted to public transport-based crowdshipping). For this computation, the load capacity of a light commercial vehicle was set at eight cubic meters in compliance with the vehicle fleets of the major national couriers operating in Rome. However, since Nuzzolo et al. [ 52] suggested that the load factor in Rome is about 50% of the transportable volume, we assume that the load value to be four cubic meters. The average dimension of the parcel has been set equal to 40 × 30 × 30 cm. This size is consistent both with the crowd (couriers) and with the typical e-commerce orders [ 53].

This paper uses the COPERT 5.1.1. (COmputer Programme to calculate Emission from Road Traffic, EMISIA SA, Thessaloniki, Greece) calculation model to estimate the environmental benefit due to lower emissions of air pollutants. Specifically, the reduction in emissions for particulate, nitric oxide, carbon monoxide and carbon dioxide are computed, thus covering both local (urban scale) and global impacts (greenhouse gases emissions).

In COPERT the emission of a vehicle i is calculated as the sum of three contributions:

E i= E hot, i + E cold, i + E vap, i

where: E hot,i: hot emissions, generated by the engine at operating temperature; E cold,i: cold emissions, generated during the engine warm-up phase; E vap,i: evaporative emissions, composed exclusively by NMVOC (Non-Methane Volatile Organic Compound).

The Emission Factor equations of the COPERT method are discussed in [ 54, 55]. Data on traffic conditions, vehicle fleet composition, kilometers traveled for each year and the cumulative value of the kilometers traveled during the lifetime are particularly important model inputs ( Table 2). In this study, vehicle fleet categories derived by the registered fleet in Rome in 2017; kilometers traveled each year by Light Commercial Vehicles (LCV) are reported in [ 56] as trend estimates based on the elaboration of different sources of data (ACI, 2000-2015 and ISPRA, 2015). Finally, the cumulative value of the kilometers traveled are computed based on the model reported in Ricardo-AEA [ 57].

Once evaluated the reduction in emissions and vehicle-kilometers traveled, traffic externalities related to local, global, acoustic pollution, and accident risk have been transformed into monetary terms. This paper uses Ricardo-AEA [ 57] and Litman [ 59] unit costs to perform this task.

The last part of the methodology implements a Cost-Benefit Analysis (CBA) calculation for the crowdshipping service in Rome. This is the most frequently used analysis for evaluating projects of collective interest and represents a useful tool for policy-makers. One can summarize the key elements of the CBA analysis as follows: (1) Investment costs; (2) operating costs; and (3) cash inflows.

The Net Present Value (NPV) is a synthetic index to express CBA results. It measures the difference between the present value of cash inflow and that of outflow over a given period of time:

N P V= ∑ t=0 n S t ( 1+i)t

where S t is the net cash flow at time t, i is the discount rate, and t the time of the cash flow. This study assumes a 3% social discount rate as set by the European Union [ 57].

For evaluating the financial sustainability of the service, the paper considers a time-frame up to 2025 and takes into account the following factors: (i) E-commerce demand growth, (ii) socio-demographic evolution, and (iii) metro network expansion. As it is for (ii) and (iii), the planning document S.T.A.T.U.S. (Transport and Environmental Scenarios for Sustainable Urban Transport) by Rome Mobility Agency has been adopted, where the long-term scenario is assumed as 2025. About the socio-demographic evolution, a very low increase (about 60,000 residents and 36,000 employees) is expected by S.T.A.T.U.S. in the long-term scenario [ 60].

For each demand scenario and each reference year, the externalities saved were estimated assuming that a certain share of orders, and therefore equivalent vehicles, are transferred to couriers (crowdshippers) using the metro network to commute to work. The reductions in environmental externalities were subsequently transformed, using unit costs, in monetary values so to calculate the ensuing economic benefits.

Considering private company profits, in line with other crowdshipping services already operating in the market, we assume that crowdshipping platform retains a 10% margin on the fee paid to the crowdshippers for the service produced. In other words, if the traveler-courier fee is € 1, the platform earns € 0.10, and the final consumer pays the delivery service € 1.10. Besides, the shipping cost for the detour the crowdshipper has to perform could also be added to the final price.

The service costs, divided into investment costs and management costs, are assessed on the base of each scenario. Investment costs refer to the purchase of automated parcel lockers (APLs) and the creation of an IT platform to manage the service. APLs are based on the daily demand and assuming each order is collected the same day: Fixing one-day pickup; the minimum number of lockers is required; thus assuming the minimum costs for the private company. Indeed, the evidence shows that collection slots have to last longer [ 14]; however, the same-day logistics is destined to expand yet further in the coming years.

Purchasing and management costs have been derived from different sources, including articles and manufacturers' brochures and websites. The average purchase cost used in this study ranges from € 11,000 for a block of 50 lockers up to € 60,000 for one of 400 [ 61]. As for the cost of the IT platform, the paper uses a flat-rate cost of € 20,000.

Operating costs include APLs maintenance and software updates. This paper assumes a €30/unit-year for the former and a flat annual rate of € 5000 for the latter. Moreover, from a mid-term perspective, it seems fair to assume that APLs management costs decrease in line with technological improvements and economies of scale. This motivates setting a € 3/unit-year reduction for lockers' maintenance.

4. Results and Discussions

4.1. Econometric Results

The utility specifications of the multinomial logit model are reported below where the two unlabeled options are defined by four attributes and the "no choice" option depends on the alternative-specific constant (ASC) and the variable "Age":

The attributes characterizing the hypothetical alternatives are: Shipping cost (typical, lower than typical), shipping time (typical, lower than typical), parcel tracking availability (yes, no), and delivery schedule date/time flexibility (yes, no).

The model fits the data well (Rho-square around 0.3, Table 3). Moreover, the sample reconstitution, i.e., the number of times the model can reproduce the right choice of the users, is equal to approximately 60%. All the coefficients have the expected signs and are statistically significant. Age coefficient is positive showing that older people are less interested in using a crowdshipping service. It is important to note that the "no choice" option can reveal not only a negative perception towards crowdshipping but also an indifference position between the two crowdshipping systems presented. In line with Cantillo et al. [ 62], further research will explore this issue.

Since attributes are qualitative and expressed in effects coding (see Table 1), one can compare the magnitude of the various coefficients. The possibility to plan the delivery date and its time schedule is the most relevant feature while having a lower shipping time with respect to the current situation has the lowest impact on utility. This reflects the fact that the actual delivery system is, in general, efficient in terms of shipping time (e.g., same-day delivery) while time windows are usually large, and people have to wait at home for their goods, producing either dissatisfaction or missing deliveries.

Data on socio-demographic characteristics, actual behavior and attitudes are also acquired. There is a high percentage of young respondents (around 40%) with a gender balance in the sample. As it is for mobility habits, by assuming a catchment area of 800m radius for each stop [ 63], one finds that 75% of the interviewees passes close to, at least, one metro station during his/her home-based trip. Other information regarding Roman citizens' mobility-related habits and activity density can be found in [ 19, 64, 65]. Most of them prefer to pick-up the parcel during the afternoon (38%) or evening (33%) and to have the withdrawal option available at least for 24 hours (44%). Many respondents (68%) self-stated a medium level of green attitude, based on the interest in/concern about environmental problems. Finally, about half of the sample foresees a successful crowdshipping service in urban areas, while only a quarter in the case of suburban areas.

4.2. Economic and Environmental Impacts

According to the results obtained, three demand scenarios have been considered ( Table 4). The "base scenario" is the one assuming the most likely configuration of the possible crowdshipping service. The base scenario is compared with others called "favorable" (with lower shipping fees) and "unfavorable" (with no flexibility in delivery date and time schedule), respectively. The probability of choosing such a service ranges from 16% to 66%.

The potential crowdshipping demand is mainly generated by the same users of the metro network, as well as by the inhabitants located in the surrounding areas of the metro stations (the latter computed adopting a catchment area of 800 m radius for each stop and reducing the number by the modal share of the metro service in Rome). Then, it is converted in potential daily orders considering an e-shopping rate of 0.0262 orders/day per inhabitant, both for the current state and the year 2025. E-shopping rate is calculated taking into account the percentage of the population making at least one online purchase, the percentage of orders requiring a physical shipment and the annual average rchase [ 66, 67, 68].

Below we report the environmental-related benefits for the 2017-2025 period, based on the above assumptions, for the implementation of a crowdshipping service in Rome ( Figure 2).

One can, on average, save 239 kg of particulates per year, with oscillation between 66 kg and 265 kg. Nitrogen oxide will, on average, be reduced by 3.76 tons per year with a variation between 1.04 and 4.17 tons. For carbon monoxide, the reduction is 2.24 tons per year with a minimum of 0.58 and a maximum of 2.49 tons. Finally, for carbon dioxide, the emission avoidance is 1098 tons per year with extreme values reaching 304 and 1215 tons.

The growth of e-commerce implies that the number of equivalent vehicles replaced by crowdshipping will increase with a consequent upsurge of emissions saved.

Without considering public benefits, the NPV obtained is negative, underlining that costs prevail over revenues for the platform operator ( Figure 3). However, considering that environmental benefits and accident reduction impact on society as a whole, it is reasonable to suppose that their economic value can be converted into public incentives and, therefore, be deducted from the total costs of the platform. Following this assumption, the NPV takes a positive sign, indicating the economics as well as the environmental sustainability of the platform during the eight years has been considered.

The biggest challenge policy-makers have to face is the redistribution of costs and benefits among stakeholders. In particular, policy-makers should provide the subsidies needed to cover platform costs due to the collective benefits it would produce.

In fact, as shown in Figure 4, if the collective benefits were converted into subsidies for crowdshipping operators were less than 100%, then a reduction in net income occurs compromising the economic sustainability of the platform. A 25% reduction in subsidies implies a non-sustainable scenario should an "unfavorable scenario" materialize. A 50% subsidies reduction makes no scenario economically sustainable.

5. Conclusions

Cities need new logistical solutions to deal with the requirements of the on-demand economy. Crowdshipping is a promising solution for sustainable urban freight distribution.

This paper provides an assessment of economic and environmental impacts of a "green" crowdshipping service based on public transport for the city of Rome, Italy. It starts with an SP survey in order to study the potential crowdshipping demand. Then, adopting discrete choice modeling, scenario analyses are performed to calculate the reduction in externalities, the revenues for the crowdshipping operator, as well as the investment and management costs for the crowdshipping platform.

The environmental assessment suggests that implementing such a crowdshipping service in Rome produces a total savings of 239 kg of particulates per year. Moreover, the economic sustainability is reached only with public incentives justified by the reduction of externalities to the society that such a system can produce.

Future research endeavors will focus on providing: (i) A more detailed environmental evaluation using micro-simulation modeling both accounting for realistic traffic conditions and availability of commercial bays, and comparing traditional versus public transport-based crowdshipping; (ii) an in-depth analysis of both technical requirements (e.g., parcel lockers location and size) and the needed coordination between shippers, logistics operators and crowdshipping platform providers; and (iii) a comprehensive analysis investigating, under a multidisciplinary approach, the full range of critical elements (e.g., economic, legal, social, psychological issues) that might hinder the adoption of a successful business model.

Author Contributions

Conceptualization, V.G., E.M. and M.N.; Data curation, S.M.P. and S.S.; Formal analysis, S.M.P. and S.S.; Funding acquisition, V.G. and E.M.; Methodology, V.G., E.M. and M.N.; Project administration, E.M.; Supervision, V.G. and E.M.; Writing-original draft, V.G., E.M., M.N., S.M.P. and S.S.

Funding

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 2. Estimation of pollution emissions saved: particulate ( a), nitric oxide ( b), carbon monoxide ( c), carbon dioxide ( d).

Figure 3. ( a) Estimation of monetized collective benefits. ( b) Net present value.

Features

Levels

Shipping fee (with respect to current national shipping companies)

● Lower (+1)

● Typical (−1)

Shipping time (with respect to current national shipping companies)

● Lower (+1)

● Typical (−1)

Parcel tracking

● Available (+1)

● Not available (−1)

Delivery date and Time schedule flexibility

● Yes (+1)

● No (−1)

EURO Class

Vehicle Category (EURO) *

km/year **

km Cumulative ***

LCV-Petrol

LCV-Diesel

MNL

Coeff. (β)

Stand. Error

t-Test

p-Value

Attributes

Age

0.0905

0.0118

7.65

0.00

* base level: "Typical"; ** base level: " Typical"; *** base level: " Not available"; **** base level: "No". [a] with respect to current national shipping companies

Model Fit Statistics
MNL

Simulation test

Demand SCENARIOS

Crowdshipping Service Adoption Probability

Potential Demand Current State (Orders/Day)

Potential Demand Year 2025 (Orders/Day)

Favorable

66.10%

14,100

29,540

Base

59.70%

12,730

26,680

Unfavorable

16.40%

3500

7330

# data[].attributes.attachment_link.title
Public Transport-Based Crowdshipping for Sustainable City Logistics: Assessing Economic and Environmental Impacts

# data[].attributes.attachment_link.description
This paper aims at understanding and evaluating the environmental and economic impacts of a crowdshipping platform in urban areas. The investigation refers to the city of Rome and considers an environmental-friendly crowdshipping based on the use of the mass transit network of the city, where customers/crowdshippers pick-up/drop-off goods in automated parcel lockers located either inside the transit stations or in their surroundings.

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Department of Forest and Wood Products Economics and Policy, Faculty of Forestry and Wood Technology, Mendel University in Brno, 613 00 Brno, Czech Republic

Author to whom correspondence should be addressed.

Received: 27 January 2019 / Revised: 2 April 2019 / Accepted: 4 April 2019 / Published: 10 April 2019

For decades, transportation has been considered as a link to all aspects of life worldwide. In this case, the world's natural environment, social well-being and economic development all usually depend on transportation systems. In most cases, safe, clean, sustainable and equitable transport systems help countries, especially in cities and urban centers, to thrive. However, a wide range of research shows that transportation systems in most of the cities and urban areas are unsustainable. In fact, some of these transportation systems are considered to be a threat to the environmental, social and economical aspects of future generations. In this perspective, therefore, changing such trends in transportation requires the collaboration of various stakeholders at regional, national and international levels. In this paper, therefore, a wide range of definitions of sustainable transport are discussed. More so, some of the aspects of smart transport for modern cities such as cycling and the role of women in sustainable transport were explored. With the aim of getting to the core of the subject, cases of women in bicycle transport, especially in the Netherlands and Germany compared to Kenya and Uganda are equally elucidated. Although not fully outlined, the idea of smart cities and sustainable transport have heterogeneous characteristics globally as discussed herein.

1. Introduction

We discuss sustainable transport in its various forms. Herein an extensive review of definitions on the subject matter is carefully studied. The aim of the study was to analyze the concepts of sustainable transport and smart cities. Also, the study aimed at showcasing the global efforts towards achieving sustainable transport and smart cities, as well as gender issues such as cycling in respect to different parts of the world, as one of the examples of sustainable transport means.

Sustainable transportation exists as one of the primary gears driving development, a trend that has existed for a long period of time [ 1]. Köhler [ 2] speculates that sustainable transport is considered to be a global concept. In fact, most developed countries continue to invest in the physical environment such as infrastructure and mobility, which are considered to be core drivers for sustainable transport. Like never before, achieving sustainable development in smart cities requires the integration of reliable transport systems. The driving factor of smart cities is to ensure the connection of human capital, infrastructure and social capital in a bid to achieve a more sustainable economic development as well as a better lifestyle for residents in these cities. In other words, sustainable transport is one of the driving elements as far as achieving smart cities is concerned. In this case, the continued steady movement of resources, be it human labor or goods across given locations, leads to domestic and global prosperity.

In their research investigation, Rassafi and Vaziri [ 3] explain that economic growth necessitates flexible transportation which eases access to resources and trade markets. Furthermore, transportation is positively linked to better standards of life through connecting people to places of education, work, health services, and recreation [ 2, 3, 4, 5]. As such, transportation is a primary concept that actuates social and economic development. However, for such rewards, there are equally reproachable effects, and for transport, these include resource depletion, pollution and over-congestion [ 3]. As such, this necessitates the need for a stable form of transport that would reduce these spillover effects, being in the form of sustainable transport. Hence, sustainable transportation ( Figure 1) is an aspect of global sustainability, which involves meeting present needs without reducing the ability of future generations to meet their needs [ 4, 6, 7].

As indicated in the study conducted by Malasek [ 8], the idea of smart cities rotates around intelligent approaches ( Figure 1) that focus on the needs and interests of people regarding economic development. Malasek [ 8] highlights that the concept of smart cities looks at the long-term element of economic development and quality of lifestyle of people living in cities. The idea is to provide improved and smarter public services, which are considered to be not only citizen-centered but also economically viable and sustainable.

In fact, there has been a number of definitions quoted for sustainable transport, but most relate to the environment, economy, and social equality [ 5]. Similarly, Zhou [ 9] stated that sustainable urban transportation would entail soliciting modes of transport that would not implicate human or environmental safety.

Furthermore, in the same report, Zhou [ 9] went on to further stress that the goals of sustainable transportation are aimed at providing mobility that safeguards regional economic development while at the same time ensuring long-lasting future for natural resources. As such in, its simplest of forms, sustainable transport would entail satisfactory to and from movement without negatively implicating the capacity of future generations. Also, the symposium on Sustainable Transport: Definitions and Responses [ 10], defined it as transport with a stable capital value, capital being of human, monetary, and natural value.

Transport Canada [ 7] also gave a detailed definition of sustainable transport consisting of three core values. First, such a system would be permitting of safe and consistent access to individual and societal basic needs, while securing both human and ecosystem health to ensure stability for future generations. Second, sustainable transport must have value for money through efficiency in operation and affordability, while offering various alternative transport means to choose from such as road and cycling routes, public buses and trains. Third and finally, the report vehemently revealed that emissions control and global waste management would be the core goals of sustainable transport. In fact, Transport Canada [ 7] further expressed the role of such a transport system in limiting the consumption of both renewable and non-renewable resources. Consequently, this would be attained through operation components of sustainable transport that would allow for justifiable resource use, recycle and reuse, control of land use and noise pollution. Ultimately, only through careful consideration for safeguarding the environment, society, and economy can this much sought after sustainability be achieved.

Scholl et al. [ 11] further defined sustainable transport as a form of transportation where consumers would have to pay their full social costs, including those that would have been paid for by future generations. Actually, this was parallel to Friedl and Steinninger [ 12], who stated that sustainable transport would have to account for the future. In fact, through careful projected estimates of future generation preferences, evaluation of cost-benefit analyses of transport volumes and modes would ensure that the net-benefit of the transport did not decline. To proceed, Scholl et al. [ 11] further stated that sustainable transport would demand changes in energy use in transport because it increases CO ₂ emissions. This, therefore, would be achieved through careful maintenance of production opportunities for the transport sector [ 2]. However, there are rather common cases where it is impossible to substitute natural capital stocks with manmade alternatives. In this case, careful steps should be taken to ensure sustainability [ 13]. Consequently, the underlying result to ensure sustainable transportation would entail a reduction in the energy and material needs required for transport [ 14]. Entirely, this would therefore stem in streamlining land use patterns, thus reducing any resulting societal need for energy-intensive forms of transport [ 11].

In discussing sustainable transportation, Zhou [ 9] stated that early focus was overtly placed on environmental degradation, and exhaustion of resources resulting from the usage of petroleum. Evidently, unsustainable forms of transport are those that directly cause harm to the environment, in both short- and long-term estimations [ 6]. More so, Zhou [ 9] argued that sustainable transportation in a way was vehemently brought forth following growing public unease over global warming, primarily after the effects of motor vehicle emission. As such, sustainable transport would entail an enhancement of vehicle fuel efficiency to reduce the amount of fuel consumed, thus lowering resulting emissions. Therefore, reducing CO ₂ emissions partaking to road transport through the use of low emission trucks and presenting incentives for less polluting transportation modes is a core value of sustainable transport [ 9]. To elaborate, examples of less polluting transportation modes popularly adhered to in the sustainable transportation model include walking, cycling, and sailing. Zhou [ 9] gave a number of other strategies, apart from reducing CO ₂, that have been adopted across the world to actuate sustainable transport as mentioned here. First, in Europe, the European Conference of Ministers of Transport (ECMT) promoted improving road safety, traffic management, marketing and telematics as a tool to enhance public transport. Furthermore, they aimed at improving the competitiveness of road transport alternatives such as trains. Also, in Canada, improvements were made to enhance the performance of carriers and operator services. Actually, this was achieved through increasing the decision-making capacity of government offices mandated with management of the transportation sector, thus bettering the management of Transport Canada operations [ 9].

In the USA, a number of government organizations have been mandated with the realization of sustainable transport, and through them, a number of approaches have been adopted. For one, transportation planners were granted strict operational freedom to cultivate the culture of sustainable transportation in the country [ 2]. Furthermore, the transportation sector was provided its own operational budget and a steady funding base to ease operation while scrupulously paying attention to accountability, thus easing transportation planning [ 9]. However, there has been a number of barriers that have limited sustainable transport across many countries in the world, as elucidated here. Transport Canada [ 7] stated that most decision making campaigns have been biased to promote already present unsustainable transportation types. Secondly, the common misconception that sustainable transportation would be economically unfeasible has further limited the successful implementation of the policy. Third and finally, the issue of soliciting a working and acceptable alternative to oil or petroleum is a major challenge, given that the suggested alternatives also implicate environmental stability. Nonetheless, sustainable transport clearly is the answer to the rather lacking present transportation entities in the world, thus suggesting strong opportunities for its wholesome adoption in the future.

Sustainable transport is one aspect of achieving smart city status. Both terminologies have a lot in common in terms of elements and outputs. They both aim at achieving better living conditions for urban communities ( Figure 1). Therefore, our study discusses this interconnection of smart cities and sustainable transport. Also, a significant focus was given to cycling as an approach for sustainable transport and smart cities with cases of women cycling in the Netherlands and Germany compared to Kenya and Uganda.

2. Materials and Methods

The study employed a content analysis technique [ 15]. This is considered to be a complex research approach practice that aims at exploiting, analyzing and coding numerous words of textual data, thus attaining valid replicated inferences [ 15]. In this study, content analysis was used as an approach to comprehend message content as the basis from which inferences and conclusions about sustainable transport research are drawn. More so, this method was unique in authenticating authorship, and this usually allowed one to determine authorship through correlating the frequencies of nouns or function words following thorough examination of prior writings by disagreeing authors [ 15, 16]. While reviewing literature, a wider range of internet sources were searched by entering keywords in popular search engines, scientific data banks such as Web of Science, Scopus and ScienceDirect among others. In a bid to easily access materials on the subject under study, the researcher used various keywords such as 'sustainable transport', 'smart transport for modern cities', and 'smart cities' to mention but a few. At this point, this method was used to analyze written literature material on sustainable transport in smart cities. In other words, content analysis methodology was used to analyze a wide range of content in the subject while applying text evaluation techniques [ 15]. Being one of the popular research methods adhered to for a multiplicity of disciplines, it was considered to be a reliable approach for this investigation.

Furthermore, this methodology helped in availing knowledge, and fresh perceptions on sustainable transport for smart cities. At this point, this was done through objective representation of facts collaborated with holistic courses of action. In this way, the transparency in this research method presented the researcher with high level of abilities to formally summarize content within written content. More so, this was coupled with competence for comprehending the author's perceptions of that material. In this case, therefore, content analysis allowed the researcher to understand the intended message from several literature materials on sustainable transport through deriving rational, and replicable assumptions [ 15].

Also, the study analyzed several cases of bicycle cycling transport from all over the world in terms of geographical location, but mainly Europe and Africa. These involved women in another case in the Netherlands, Germany, Kenya, and Uganda. Global perspectives were also captured and discussed extensively. Both approaches are qualitative in nature [ 17]. Also, qualitative investigation methods have main essentials of narrative research, phenomenology and case studies among others.

3. Literature Studied

3.1. Smart Transport for Modern Cities

The ever persistent trend of global development has primarily been a result of progressive infrastructure development to meet the constantly evolving modern demands by any given population. In fact, it is imperative for any given modern city to sustainably develop transportation systems to further advance any intended prosperity. Rassafi and Vaziri [ 3] stated that infrastructures solicit critical public services, essential for economic development and improved standards of living. More so, the same report reveals that a majority the global populated cities contribute a staggering 80% to global GDP (Gross Domestic Product). As such, this therefore affirms without a doubt that these modern urban cities to a large degree are the cornerstone on which global development is hinged. However, there comes risks of such large numbers primarily in the form of transportation. To elaborate, Dia [ 7, 18] stated that traffic congestion costs an average of 1-3% of a country's GDP while the global road fatality rates soar at 1.2 million and cost USD $100 billion per year. Ultimately, modern cities have gone the extra mile to establish smart transport systems to enhance the flow of urban traffic better while improving the mobility of their inhabitants. Recently, it has become a trend for many modern cities to transition into the digital age through purposeful integration of information and communication technologies into transportation and administration at large [ 7, 18].

More so, the study further revealed that the fundamental mass transit systems for a number of modern cities are trains, subways, and buses. To elaborate, in Singapore, the Mass Rapid Transit (MRT) is the nation's flagship smart transportation transit solution to the demanding masses. While looking at the numbers, the system's efficiency sees over 2.5 million people from the nation's total population of 3.5 million using its services daily. In fact, over 100 stations in Singapore use MRT, with trains having 5-minute intervals between each other. Thus, subway and train systems are a fundamental smart transportation feature for many modern cities, with regular improvements being made to the system annually on a global scale.

On the same note, Olaverri [ 20] further stated that vehicle-to-pedestrian and pedestrian-to-vehicle information systems are ultimately aimed at improving road safety by issuing warnings to application users on impeding collision risks. In this case, this form of road safety campaign has been vigorously researched, with most of the modern cars being equipped with motion detection softwares together with automatic braking systems. Likewise, Sugimoto et al. [ 22] explained that most of the invented wireless local area connection communication systems are used to alert pedestrians, thus warning them of collision risk.

Cycling is a common form of smart transportation commonly practiced in modern cities. In many countries, public bicycle systems under local governments or non-governmental organizations have been set up to share bicycles amongst inhabitants. Hirst [ 19] associated cycling with reduced traffic congestion, considering cyclists have individual cycle lanes. Also, the same report affirms that cycling reduces pressure on public transport, while improving the individual health of inhabitants who regularly use this mode of transportation. In the same light, Banks [ 23] revealed that over half of the inhabitants in Copenhagen commute by bike. As such, to support this, over 380 smart traffic signals have been installed all over the city to give cyclists first priority to speed up their mobility times through traffic. Hence, Copenhagen achieved a 10% reduction in travel times through cycling, a common trend steadily catching on through the whole nation at large [ 24]. Similarly, the United Nations Commission on Science and Technology for Development [ 21] also stated that in Budapest, a cycling network consisting of 98 stations to rent and over 1000 bicycles was established with a success rate of over 1 million rentals.

In truth, modern city traffic is significantly composed of large vans and delivery trucks doubling the routine of carrying goods and products between a multiplicity of stores and shops, a strenuous routine [ 19]. Thus, therefore, smart transportation offers remedial alternatives such as the exploitation of rail systems and water freighters to transfer and distribute products on demand to different modern cities. Ultimately, through cycling and electric vehicles, these goods are then supplied to individual households. In this case, smart transportation helps smoothen trade. Hence, smart transportation systems have been generally attributed with positive rewards in the different modern cities where such projects have been implemented. Hirst [ 19] similarly revealed that implemented smart transport measures in the United Kingdom were provided an investment for energy efficiency and waste management development under the European Union Cohesion policy estimated at £100 million for London and £100 million for North West England respectively.

Furthermore, the same report stated that the wireless electronic parking permit system, a particular form of smart transportation implemented in a section of New York saved the government a massive USD $8 million from a mere USD $50,000 investment. Similarly, Banks [ 23] found out that over 380 smart sensors were installed in Copenhagen to ease mobility for the large cycling faithful of the city. In this case, the sensors detect a group of cyclists headed towards a busy intersection, then signal the traffic lights to turn green thus allowing them safe passage through. More so, the sensors went on to study the cyclist's speed data based off recordings from camera, then adjusted the timings of the lights to further increase travel time. Primarily, he was of the view that enhancing mainstream traffic lights systems with digital sensing and communication technologies lessened traffic delay times by over 40%. In this case, this enormous improvement was attributed to the digital feature that allowed cars to be the control panel for the traffic light, unlike the traditional opposite. Thus, traffic lights have a fundamental role in actuating smart transportation for modern cities.

Also, traffic control systems are designed to account for public transport priority as a form of smart transportation for modern cities. In this case, a report for the European Union by CIVITAS [ 25] revealed that traffic control settings are implemented to allow for less stops by buses at traffic lights. In fact, the traffic systems are programmed in such a way that signal priority to buses does not to a large degree negatively impact traffic flow of other road users such as cyclists and pedestrians. To actuate this, CIVITAS [ 25] stated that two approaches are adhered to for fluid implementation of public transport priority. First, the passive control system allows for public transport vehicles to smoothly move without stopping, thus bypassing the system easily. Second, for the active system, traffic light signal timing is adjusted in real time based off the expected arrival of the desired public transport vehicle at the intersection, hence this is the more vigorous form of the system. To elaborate, such systems have been implemented and actively used minimally in Toulouse in France, with future options for full integration citywide. Ultimately, the results revealed a significant 52% reduction in waiting times at traffic lights for public transport systems, thus a successful smart transportation module for modern cities.

Benevolo et al. [ 26] also stated that technological advancements have allowed for the development of hybrid cars and car-sharing as similar examples of smart transportation for modern cities. In fact, as a core underlying value of smart transportation, hybrid vehicles that partly alternatively use electricity, would allow for reduced emissions resulting from motor vehicles. Also, the car-sharing social platform works through allowing inhabitants of modern cities to reserve vehicles of choice, driving it and returning it from the point of picking while incurring a reasonable fee for service costs. Ultimately, Benevolo et al. [ 26] affirmed that this form of smart transportation kills two birds with one stone through allowing for emissions control while at the same time reducing traffic congestion in modern cities.

3.2. Cycling for Sustainable and Smart Cities

Larsen [ 33] also revealed that it was observed on Sundays in Mexico City that over 15,000 cyclists cycle in unison through the city while following along the established cycle lanes in the city. Mexico City is among the worst affected cities in the world as resulting from traffic congestion with the average rush hour speed of a car being 4 km/h [ 38]. The same report extensively states that Mexico City has since introduced a bicycle sharing system through ECOBICI (Eco Bikes sharing system) while introducing over 170 kilometers of cycling lanes and hubs to further support cycling. ECOBICI received considerable public attention with over 265,000 registered users and about 35,000 daily trips cycling trips by inhabitants of Mexico City, with a recorded increase in bicycle trips of over 500%.

In this case, this can entirely be down to two reasons, the first being that bicycles occupy little space and are hence easy to navigate, and also the expansive cycling lane systems which make it easy to reach such places. Marqués et al. [ 41] were of the same view after they observed an increase in the number of cyclists in Seville following the growth of isolated cycling lanes for the period 2006 to 2011. Resultantly, the number of people whose commute was by bike surged considerably even though Seville had no prior history of cycling. Hence, sustainable and smart cities must have necessary infrastructure development to readily accommodate cycling for it to have full prosperity.

Most modern cities are ultimately designed to be traversed with cars. In this case, therefore, planning is made largely for large distances, hence mobility of using bicycles is hard in such cities. It is beyond doubt that most of the urban plans for sustainable and smart cities largely center on cars as the primary form of transportation [ 40]. Hence, it is imperative for any given city venturing into cycling to invest a considerable amount of effort and wealth in establishing necessary infrastructure that secures safety while allowing for efficiency [ 31]. This security has been offered by the cycling lanes and bike-sharing systems which always puts cyclists first as the center of traffic on roads in these cities that staunchly practice cycling.

Larsen [ 33] revealed that theft and vandalism had hampered the success of cycling for a number of cities, but the modern bike-sharing systems offered remedial solutions to this problem. In most cases, the mode of operation and management of bike-sharing systems has purposely over time evolved to account for securing the safety and durability of their merchandise. Gasiorowski [ 38] also stated that cycle parks account for anti-theft through using lock mechanisms on their bikes that lock the bicycle frames to cycle parking stands thus securing the bike.

On the same note, Larsen [ 33] highlights that modern bicycles popularly used in the bike-sharing systems are specially made from unique material that would fetch little to no value if stolen and sold by a thief. Furthermore, other bicycles come equipped with GPS trackers which emit radio frequency, allowing for constant monitoring and tracking, thus prohibiting theft. More so, the fact that the only way of accessing a locked bicycle for most systems is after payment by credit card payment or use of membership smartcard ensures safe storage for these bikes. It is common for a majority of systems to allow the rider a specified period of use following payment. Hence, the cyclists can select bicycles from the securely placed bicycle racks or docking stations and return them back after the user's time has expired. In this case, it is not surprising that research indicates that bike-sharing continues to experience the fastest growth as one of the modes of transport [ 33].

Traffic congestion is a serious global issue, with a number of major world cities succumbing to it in one way or the other. In this case, many people opt to use bicycles as a quicker mobility option. Gasiorowski [ 38] speculates that a multiplicity of urban cities are plagued with traffic congestion, with cycling offering a remedial solution to this issue whilst improving the health of the cyclist. In Annecy, France, a great percentage of in city trips are made by bike, which is affordable unlike cars and are thus owned by the majority of the population.

Also, given the fact that modern cities are space sensitive, bicycles take up less space than cars, and their parking is much easier and convenient. Truthfully, a cyclist will park their bicycle at a bike-stage close to their destination as opposed to vehicle parking slots which are hard to come by. Gasiorowski [ 38] further implicates cycling with better and improved health of cyclists since it is a reliable source of physical exercise. Indeed, cycling improves cardiac health through allowing for regular muscle exercise, along with expanding lung capacity, thus generally improving population health. Todhunter [ 34] was of the same view as far as the contribution of cycling to health is concerned. The more people ride, the more chances they stand to be healthy ceteris paribus.

Pinna et al. [ 42] observed a surge in the use of bicycles by inhabitants of major Italian cities. Consequently, the report revealed that cycling was very popular in northern Italy with a number of cycle lanes connecting a number of different locations within these cities. Furthermore, bike-sharing programs were also seen to have expanded recently from one city in 2005, Bologna, to over nine by 2010. In truth, the report vehemently expresses the fact that ongoing plans are already in place to further extend bike-sharing schemes to other cities across Italy as per directive by the Italian national government. Also, Pinna et al. [ 42] explained that the number of bikes available for cycling in these bike-sharing cities significantly increased.

In truth, sustainable transport such as cycling has a lot to offer to most smart cities across the globe. For example, efficient cost-friendly mobility routines usually offer easy connectivity within and around smart cities. However, there is a need to scrupulously adhere to a number of measures to ensure a prolonged actively functional cycling culture in sustainable and smart cities. Poppe [ 32] stated that it was crucial for cycling lanes to have high connectivity even to the city while operating separately from main roads to ensure utmost safety. Furthermore, it is important for the traffic lights systems to be bike-friendly, with the ability to detect cyclists along busy streets and intersections, signposts along roads. Finally, there should be bike management facilities and parks.

Nonetheless, cycling continues to be one of the most common transportation means across the globe that comes with a range of health, social and environmental benefits. In fact, Garrard et al. [ 43] highlighted that cycling is an active mode of transport that most developed countries continue to harness and use. However, Garrard [ 44] explained that cycling among women in some countries is still limited because of substantial gender differences. According to Garrard et al. [ 45], cycling among women has always contributed to their social inclusion since it offers them an affordable and at the same time convenient mode of transport. [ 43] claimed that in most European countries, women cycle more frequently than men. In most cases, traffic safety usually acts as bottlenecks for women to fully participate in cycling.

3.3. Role of Women in Sustainable Transport

According to Kronsell et al. [ 6], the role of women and transport has attracted the attention of many city leaders across the globe. However, studies indicate that there are various factors that affect women when it comes to public transport [ 48]. As a result, many countries have allowed women to participate in finding better solutions for sustainable transport. Based on the United Nations Global Sustainable Transport Conference [ 1], there is a great link between women, transport and employment patterns in most urban areas. In other words, sustainable transport systems are considered to be the fulcrum, which allows most women in various cities to participate in the economic development of their countries. As much as this remains true for most smart cities, most women in some countries such as India rely heavily on public transport or walking. Nonetheless, women continue to play a significant role in transport policies and systems despite their limited level of participation. Therefore, it is not surprising that the United Nations Global Sustainable Transport Conference [ 1] recommends an inclusive approach for sustainable transport in various countries, especially in urban centers.

In the study conducted by Kunieda and Gauthier [ 50], women play a critical role in current transport infrastructure. In most cases, women are always concerned with the safety and personal security element of transport. In this case, women have been the source of policies that drive sustainable transport in most cities. More so, Kunieda and Gauthier [ 50] explained that better transportation systems have always contributed to people's quality of life in a given society. In this case, allowing women to participate in policymaking, especially on sustainable transport, has brought economic growth and efficient transport systems in most cities.

Furthermore, Root et al. [ 51] speculated that this change is largely attributed to the changing role of women in various societies, especially in modern cities. According to Kronsell et al. [ 6], most of the modern cities are experiencing a significant increase in the number of women entering the workforce. As a result, this has increased the roles or importance of women in the process of making transport policies. More so, it is worth mentioning that the increasing number of women on the road has a great implication on the sustainability of transport based on these policies. In other words, there is no doubt that an issue of women in terms of the approaches in which transport policies are devised cannot be ignored. In his study, Buckingham [ 52] depicts that involving women in sustainable development is one of the key elements that can help change the world based on the level of new demands. In this perspective, transport cannot be ignored in any level of sustainable development. It is from such a background that [ 10] paints that the role women have in sustainable transport is increasing in one way or the other.

Despite the improvements in travel patterns and the role of women in sustainable transport, their contribution is still less compared to men [ 53]. For example, women still tend to have shorter commutes, especially in terms of time traveled and distance. As a result, this continues to limit their influence in policies that can favor them in one way or the other. As Root et al. [ 51] posited, the limited participation of women in sustainable transport is often explained while looking at the aspects of socio-economic issues they face. For example, most women in various countries still have access to private vehicles, and others are overwhelmed by domestic work. In this case, such circumstances limit them from playing bigger roles in the process of formulating sustainable transport policies that can transform their cities like never before.

According to Aljounaidi [ 53], women still have less control over resources, and this usually limits them from accessing private means of transport. In Gaza and Yemen, for example, Aljounaidi [ 53] explains that most women still struggle to use public transport despite the challenges amidst the services. Some of the challenges women in Yemen and Gaza face as far as transport is concerned include costs, timing and routing. In addition, most women who live in rural areas usually find it challenging to access sustainable transport while going to and from work. Just like Aljounaidi [ 53], AFCAP [ 54] explains that most governments in developing countries are working hard to promote the role of women in the transport sector. In countries such as Ghana, women are getting involved in providing transport related services, and some are appointed as managers at different levels. Nonetheless, studies indicate that women's involvement in sustainable transport is generally still low because of several reasons [ 53, 54]. For example, most women lack enough money to afford to pay for services or buy their own vehicles. In fact, this explains why there is a higher incidence of walking to work among women compared to men.

Furthermore, AFCAP [ 54] paints the transport sector as one of the sectors that are most gendered in many of the African countries. In fact, most commercial drivers, people involved in transport management and bus conductors, to mention but a few, are male. According to Aljounaidi [ 53], social factors, which are imposed on women's mobility in most of the African countries are so high that they always impact on the role of women when it comes to transport infrastructure as well as services.

4. Cases of Women in Bicycle Transport: The Netherlands and Germany Compared to Kenya and Uganda

This section explores how the Netherlands, Germany, Kenya and Uganda have made bicycling among women a possible or inconvenient, and practical practice to move around their cities. The analysis relies on the available information collected from a wide range of online databases, and mostly scientific sources such as Scopus, Web of Knowledge Information collected on each of these case studies highlights the key factors helping or affecting levels of cycling among women as one of the factors facilitating sustainable transport and smart city options.

4.1. Case of the Netherlands

While reflecting on the study conducted by Pucher and Buehler [ 55, 56] and Harms et al. [ 57], the Netherlands remains one of the most famous countries known for its high levels of cycling. According to BBC Magazine [ 58], most cities in the Netherlands have high levels of cycling compared to other countries across the globe. In this case, the success of cycling in these countries usually depends on favorable policies implemented by governments. For example, Pucher and Buehler [ 56] speculated that the Dutch government motivated various companies in the country to pay people to cycle while going to work. More so, the same research shows that the government encouraging cycling in a bid to fight congestion on the roads. Cycling infrastructure is one key element that has enabled the Netherlands to embrace cycling as a sustainable means of transport ( Figure 2). The Netherlands also has parking structures for bicycles on all the bus stations, railway stations, and most buildings across the country. Cycling culture in the country is very developed, with less stereotypes attached to gender or age. Women and children embrace riding whether it is raining or shining [ 55, 56, 58].

In their study, Pucher and Buehler [ 59] depicted that Dutch and other western countries take cycling to be practical and utilitarian. In fact, it is not surprising that there are more bicycles in the Netherlands than residents, especially in cities such as Amsterdam and Hague. BBC Magazine [ 57] indicated that more than 70% of the journeys made by men and women are by bicycles. It is such sustainable transport approaches that continue to help the Netherlands to have smart cities. Cycling for both men and women and integration of technology are enablers of smart city transport measures.

For both men and women, Pucher and Buehler [ 56] added that most cities in the Netherlands lead the way as far as cycling is concerned. For example, it is estimated that there are more than 22 million bicycles in the country. Surprisingly, there are about 17.1 million people who live in the Netherlands, and more than a quarter of the people cycle to work. Women participate equally with their male counterparts when it comes to cycling. Pucher and Buehler [ 56] painted that since 2005, the number of bicycles in the Netherlands has increased by more than 10%. In Amsterdam, for example, it is indicated that 32% of men and women journey by bike. More so, the government of the Netherlands implemented financial rewards in a bid to motivate people to cycle frequently. However, after the financial rewards stopped, many people continued to cycle, especially when going to work. It is worth mentioning that cycling has helped employees in the country to maintain good health as well as flexibility in their movements especially in and around the cities.

4.2. Case of Germany

With the aim of encouraging many people to switch to cycling, Germany is promoting cycling among men, women and the youth [ 59]. For example, it is indicated that Germany has improved express roads for cycling to make it easier for everybody to cycle, and this contributes to achieving 'smart city' status. As BMVI [ 59] explains, most of the cycling superhighways implemented by Germany are well suited for urban areas. As a result, this has motivated many people, especially women, to cycle even when going to work. In this case, it is not surprising that the government of Germany is providing an annual €25 million dedicated for improving cycling superhighways.

4.3. Case of Uganda

In Uganda, cycling among women is not common. In fact, bicycles are commonly used in rural areas where young men use them for transporting commodities, especially cash crops to the markets. More so, bicycles are intensively used in Northern and Eastern Uganda compared to Western and Central areas. According to New Vision [ 60], very few women cycle in Uganda, and this is attributed to the terrain and cultural beliefs regarding women in most parts of the country. For example, in some cultures (rural areas) in Uganda, some people still believe that women are not supposed to cycle. The reason is that their culture prohibits them from sitting with their legs apart.

4.4. Case of Kenya

Just like in most of the developing countries, a reliable means of transport is considered to be one of the core factors in economic development in Kenya. According to Alando and Scheiner [ 62] cycling in most cities in African countries including Kenya faces unending exclusion, especially from the street spaces. Much as cycling is one of the cheapest transport means in East African countries, there is still limited infrastructure that supports cycling in the country. Besides general challenges, women in Kenya still experience exclusion when it comes to the transport sector [ 62]. In fact, few women cycle as many are limited by cultural beliefs that women are not supposed to ride bicycles. In this case, therefore, it is worth mentioning that these cultural beliefs continue to limit cities like Nairobi and other developing countries when it comes to achieving sustainable transport and smart city status.

5. Discussion and Conclusions

Based on a wide range of literature reviewed, it is worth mentioning that sustainable transportation remains one of the core drivers for socio-economic and environmental development across the globe. More so, various definitions have been explored in a bid to understand all aspects that rotates around sustainable transport in smart cities. For example, one of the definitions of sustainable transport capture three core values, which are basic for most people to understand. First, such a system would be permitting of safe and consistent access to individual and societal basic needs, while securing both human and ecosystem health to ensure stability for future generations. Second, sustainable transport must have value for money through efficiency in operation and affordability, while offering various alternative transport modes to choose from. Thirdly, it should be environmentally friendly in terms of GHG emissions among other variables.

In all three core values, it was revealed that sustainable transport focuses on the ability of societies to make development sustainable while ensuring that it meets the needs of the present without compromising those of future generations. On the same note, it was noted that any unsustainable forms of transport are those that directly cause harm to the environment, in both short- and long-term estimations. In other words, sustainable transportation is a primary concept that actuates social and economic development. Thus, various studies concluded that sustainable transport clearly is the answer to the rather lacking present transportation entities in the world, and this suggests strong opportunities for its wholesome adoption in the future.

When it comes to smart cities, it was highlighted that the ever progressive infrastructure developments must be sustainable as well. More studies indicated that smart cities require flexible transportation systems such as cycling. However, this investigation revealed that smart solutions for smart cities requires safe infrastructure and integration of technology to allow travelers to get more connected while monitoring their movements. Sustainable transport is one aspect of smart cities and contributes to numerous other components that make up a smart city. Both sustainable transport and smart cities' main goal aims at facilitating a better life for the communities in the cities especially with reducing carbon emissions, and when it comes to bicycles, they are ranked cutting edge, and the same goes for the food-print of excess energy used when cycling.

In this paper, we concentrated on understanding the major concept of 'sustainable transport and smart cities'. However, we zeroed on one aspect which is cycling and the role women play herein, with many examples and cases given from given countries ( Figure 1).

Cycling is a common form of smart transportation commonly practiced in modern cities. In many countries, public bicycle systems under local governments or non-governmental organizations have been set up to share bicycles amongst inhabitants to allow traffic flow. A wide range of examples of smart cities were cited, as well as the mode of transport such cities are using. For example, it was found out that most of the modern Western cities have gone the extra mile to establish smart transport systems to enhance the flow of urban traffic better while improving the mobility of their inhabitants. On the same note, it was indicated that it has become a trend for many modern cities to transition into the digital age through the purposeful integration of information and improved infrastructure.

However, most of the transport systems being implemented by various cities still face several bottlenecks. For example, much as cycling system is doing well in most of the Western countries such as the Netherlands, the majority of developing countries face many challenges. To rigorously support cycling, there is a need for infrastructure development such as building cycling lanes and bridges to accommodate this smart transportation, funding which might not come cheap for many cities. Nonetheless, smart transportation offers flexibility and greener transportation alternatives for a multiplicity of modern cities, and is thus a great necessity. More so, it is beyond doubt that most of the urban plans for sustainable and smart cities largely center on cars as the primary form of transportation. Nonetheless, it is imperative for any given modern city venturing into cycling to invest a considerable amount of effort while focusing on establishing necessary infrastructure that is secured and at the same time sustainable.

For women in transport, it was indicated that women play a critical role in current transport infrastructure. In most cases, women are always concerned with the safety and personal security elements of transport. More so, several studies [ 35, 51, 57] indicated that better transportation systems have always contributed to people's quality of life in a given society. In this case, allowing women to participate in policymaking, especially on sustainable transport, has brought economic growth and efficient transport systems in most cities. Further studies revealed that despite the improvements in travel patterns and the role of women in sustainable transport, their contribution is still less compared to men. For example, women still tend to have shorter commutes, especially in terms of time traveled and distance. As a result, this continues to limit their influence over policies that can favor them one way or another.

With the aim of getting to the core of the concept, various cases have been explored. Some of these cases represent Western countries and other African or developing countries. Western countries where they have achieved a high level of sustainable transport in smart cities include the Netherlands and Germany. On the other hand, Uganda and Kenya cases represented developing countries, especially on the aspect of women in cycling as mode of transport in smart cities. Based on various cases of women cycling, it is worth mentioning that the Netherlands continue to lead Germany, Kenya, and Uganda. More so, research indicates that cyclists in the Netherlands and Germany [ 57] have better infrastructure when it comes to cycling as compared to East African countries (Uganda and Kenya).

Compared to Germany and the Netherlands, Uganda and Kenya have different backgrounds in terms of bicycle transport. We observed that it is very normal and healthy for both women, men and children to ride for health, environment and transportation in the former, while in Uganda and Kenya, women are not accepted as far as riding bicycles is concerned. In some cultures, it is even completely prohibited. In general, most African families do not allow the girls to even learn how to ride. It is in the most recent times that actually women can comfortably ride bicycles in Africa, and yet they still face a lot of societal unacceptance, and are sometimes laughed at or even abused if not punished. Additionally, its considered transport for poor people in most African societies.

Nonetheless, this research revealed that cycling is not the only element that can help cities to develop sustainable transport systems. In fact, it was indicated that cities need to build strong partnerships with various actors in a bid to enable the smart city level. Based on this investigation, sustainable transport for smart cities require research and innovation in both big and small cities. In this case, smart cities should aim at engaging all citizens with better policies, and by bringing together hard infrastructure, local skills, social capital and technology to mention but a few. It is through setting up safe infrastructure, the integration of technology and women inclusiveness in the transport sector that Kampala, the capital city of Uganda, can start the journey of becoming a smart city, and the setting goes for other aspiring cities.

For cities like Nairobi, Kenya to become one of the smart cities in the world, the current transport sector should be reshaped to experience a paradigm shift. In one way or the other, this paradigm shift should focus on achieving smart city objectives including the integration of technology in transport systems, public bicycles and bike-sharing to mention but a few. Nairobi, the capital city of Kenya, can achieve smart city status by ensuring that travelers including women in the city are more connected. In other words, all public transport users such as cyclists and those using vehicles and other means can use technology to monitor their movement. Various benefits including traffic flow and other health advantages for both men and women can be achieved.

For example, with its high cycling mode share, there is no doubt that the Netherlands has better policies and motivations that encourage people to cycle on frequently. In fact, research indicates that women in the Netherlands cycle more than men. As indicated in the above case studies, there is a significant difference between the Netherlands, Germany, Kenya, and Uganda as far as women in cycling transport is concerned. For example, the Netherlands and Germany have made it easier for women and men to cycle by providing advanced infrastructure that favors cycling. In Uganda and Kenya, cultural differences continue to limit women from cycling, and there is still poor infrastructure for safe cycling. Despite the challenges, sustainable transport clearly is the answer to the rather lacking present transportation entities in the world, thus suggesting strong opportunities for its wholesome adoption in the future.

Much as the study provides a comprehensive analysis of sustainable transport for smart cities, there is a wide range of drawbacks that limited this investigation. One of the limitations is that the scope of the study is limited to a few cases, especially Germany, the Netherlands, Kenya, and Uganda. Notwithstanding the fact that sustainable transport for smart cities presents complex aspects regarding economic development, this study focused much on cycling. Nonetheless, this study addressed the existing gap in literature regarding sustainable transport for smart cities. However, more research with wider case studies and primary information should be carried out to shed more light on this subject.

Author Contributions

Conceptualization, D.B.; methodology, D.B.; software, D.B.; validation, D.B. formal analysis, D.B.; investigation, D.B.; resources, D.B.; data curation, D.B.; writing-original draft preparation, P.H.; writing-review and editing, D.B.; visualization, D.B.; supervision, PH.

Funding

This research received no external funding

Acknowledgments

The study is highly indebted to Edison Turyatemba who helped in proof reading as well as his paramount comments and recommendations.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The inter-connection between sustainable transport and smart cities.

Figure 2. Cycling in the Netherlands-Deventer City.

Figure 3. Cycling in Uganda (Photo credit: Amanda Ngabirano).

# data[].attributes.attachment_link.title
Analysis of Sustainable Transport for Smart Cities

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For decades, transportation has been considered as a link to all aspects of life worldwide. In this case, the world’s natural environment, social well-being and economic development all usually depend on transportation systems. In most cases, safe, clean, sustainable and equitable transport systems help countries, especially in cities and urban centers, to thrive.

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ABSTRACT

ABSTRACT
This paper investigates where and how sustainable transport goals are translated into public transport planning and operations. The case where this is explored is the Regional Public Transport Authority (RPTA) in Stockholm, Sweden. By drawing upon recent discussions on policy translation and political-administrative relationships, sustainable transport is found to be translated in two different collaborative spaces in the RTPA. In the market side of the authority, which is mainly preoccupied with procurement of traffic and compliance issues, sustainable transport is translated into quantitative goals (including biofuels, emissions, noise, etc.) and mechanically reproduced from the politicians via the civil servants to the private operators. In the planning side of the authority, sustainability measurements have been hard to quantify and the challenge to integrate land-use and transport planning is resolved in an organic manner, in specific projects, between the strategic transport planners in the RPTA and the land-use planners in the municipalities, at a distance from the politicians' involvement. Throughout the RPTA, sustainable transport has broadened to also include social sustainability, although this has been difficult to translate into quantitative measurements, which is the desired mode of governance by the politicians.

Introduction

During the last three decades, sustainability has emerged as an overarching societal goal across the globe, crossing different sectors and policy fields. Transport stands out as one of the policy fields that perhaps face the greatest challenges. According to IPCC, transport is responsible for roughly 23% of total energy-related CO ₂ emissions (Sims et al., 2014, p. 603). Despite more efficient vehicles and new mitigation policies being implemented during the past decades, the level of greenhouse gas emissions from transport has continued to grow globally.

Public transport plays an important role in lowering the transport sector's levels of CO ₂ emissions and increasing its energy efficiency (Sims et al., 2014). To reduce greenhouse gas emissions from passenger and freight transport, IPCC presents four main mitigation strategies that policy-makers could pursue: (1) avoiding journeys where possible, (2) a modal shift to lower carbon transport systems, (3) lowering energy intensity and (4) reducing carbon intensity of fuels (Sims et al., 2014, p. 603). Public transport is mainly concerned with realizing the second strategy, i.e. increasing its market share of total motorized transport. But the third and fourth strategies are also of relevance as non-renewable fuels are increasingly being substituted by renewable ones in public transport, and as newer vehicles replace older, their energy efficiency increases.

Public transport is comparatively more sustainable than other modes of motorized transport (Banister, 2008; Sims et al., 2014). Yet, public transport authorities across Europe are increasingly being expected to respond to the global ambitions of transforming their activities and operations so that they become sustainable in and of themselves. But how do they respond to this challenge and where is sustainability translated into their activities and operations? This paper seeks to probe the question how and where sustainability is translated in the context of public transport by studying the relationships between politicians and civil servants in the Regional Public Transport Authority (RPTA) in Stockholm, Sweden.

Sustainability is perhaps one of the most used and misused concepts in political and corporate discourse (Farley & Smith, 2013; Redclift, 2005), plagued as it is by a myriad of indicators and incommensurable metrics (e.g. Lyytimäki, Tapio, Varho, & Söderman, 2013). Critical research on sustainability has, moreover, suggested that sustainability has undergone so much mainstreaming that it virtually has become depoliticized. Since hardly any group would oppose the idea that the survival of humankind and the planet is vital, this makes sustainability an empty signifier, whose meaning is so ambiguous that it may be used to mean anything (Avelino, Grin, Pel, & Jhagroe, 2016; Kenis & Lievens, 2014; Kenis, Bono, & Mathijs, 2016; Swyngedouw, 2010). Moreover, studies have found that, when global sustainability policies are translated and subsequently operationalized into national policies and organizational practices, they tend to collide with local knowledge and institutionalized routines, leading to the emergence of trade-offs and thereby exhibiting its political implications (Temenos & Mccann, 2012; Uittenbroek, 2016).

Previous studies on collaboration in the governance of sustainability have predominantly focused either on horizontal relationships between different stakeholders or governmental entities (e.g. Hull, 2008; Lafferty & Hovden, 2003), or on vertical relationships between different levels in multi-governance structures (e.g. Bulkeley & Betsill, 2005; Newig & Fritsch, 2009). But little has been done when it comes to empirically investigating the governance structures and collaborative efforts between politicians and civil servants in the context of translating the concept of sustainability (see e.g. Lange, Driessen, Sauer, Bornemann, & Burger, 2013; Meadowcroft, 2007). This paper intends to fill this gap by investigating how collaborative spaces shape the interpretation and definition - that is, the translation - of the concept.

Interpretative policy analysis has questioned the idea that policies and planning concepts are 'transferred' from one context to another (Dobbin, Simmons, & Garrett, 2007; Dwyer & Ellison, 2009; Stone, 2012). By studying translation both as a social process and as assemblages, interpretative policy analysis has developed and sensitized the understanding of both policy transfer and implementation (Yanow, 2007; Clarke, Bainton, Lendvai, & Stubbs, 2015). Some of these works draw inspiration from Callon's ( 1986) seminal study that sparked the study of the sociology of translation, to which I will return in a moment. Even though the translation of sustainability and transport policies has been studied before (e.g. Boussauw & Vanoutrive, 2017; Lagendijk & Boertjes, 2013; Montero, 2017), the collaborative spaces in which translations occur have, as mentioned earlier, only received little attention. By connecting the literature on political-administrative relationships (Overeem, 2005; Svara, 2006a, 2006b) with the one on policy and planning translation (Clarke et al., 2015; Healey, 2012; Healey, 2013; McCann & Ward, 2011), this study will contribute with new knowledge on how sustainability is translated in the political-administrative nexus in the context of public transport.

The outline is as follows. I begin by describing the methodology used to collect the empirical material and continue by reviewing the theoretical debates and by defining the key concepts needed to analyse the material. Then, I proceed to describe the background and context. This is followed by narrative accounts of civil servants, who describe their relationships with the political level in the County Council of Stockholm, as well as their collaborations with the procured traffic operators and the local planners in the municipalities. Finally, the conclusion and results are presented.

Methodology

The question guiding this paper is explored through a unique case study: The RPTA in Stockholm. Stockholm is often seen as a successful case in both public transport and environmental policies. Its metro system has been heralded as a good example of how to integrate public transport and land-use planning (e.g. Cervero, 1998). In 2010, Stockholm was also the first city to be entitled the Green Capital of Europe, an annual award granted by the European Commission's DG Environment (European Commission, DG Env, 2017). While recognizing that success and failure are far from neutral labels, constructed as they are in political-cum-ideological processes (McCann & Ward, 2015; Peck, 2011), Stockholm was here chosen not because it has been labelled a successful case per se, but because this labelling enables an investigation of how and where sustainability - being understood as an empty signifier - has been translated.

This case study is built upon interviews and public documents. Six in-depth interviews were taped and transcribed during late 2015 and early 2016. Patterns and recurring themes were identified and further analysed. The interviewees worked predominantly in the Department of Strategic Development in the RPTA. Two of the interviewees worked as managers in the department and had comparatively closer contact with the politicians than the rest of the strategic planners. As the staff in the Department of Strategic Development were strategically located within the organization, they also had a broad overview of the entire organization, which ensured reliable interview material.

Besides 'following the people' and understanding how they make sense of and translate sustainability, I have also been 'following the materials', and so traced how sustainability has been translated in key documents (Wood, 2015b). Public documents, including decision-making protocols and sustainability strategies, were also collected and analysed. The documents covered a period of approximately 10 years, stretching from the first sustainability strategy in 2004 to the Global Compact Communication on Progress Rapport in 2014. This allowed me to gain insights into the relationships between the politicians and the civil servants as well as insights into how the translation of sustainability has changed over the years. Following the purpose of the paper, the questions guiding the analysis of the empirical material were twofold: first, how has sustainability been translated from 2004 and onwards and, second, where, in which collaborative spaces, have these translations occurred?

Theorizing the collaborative spaces of policy translation

The theoretical discussion builds on the rich debates about the political-administrative relationship, as it has been discussed over the past 10 years. Policy translation is here understood as taking place in the collaborative spaces where politicians and civil servants meet, exchange documents and work together. The theoretical contribution of this paper lies in the connection between the research on the political-administrative relationship and its potential synergies with policy translation studies.

The political-administrative relationship

The political-administrative relationship is a classical topic of discussion that resurfaces time and time again. It received a renewed interest in the mid-2000s when Svara ( 2006a) suggested that politicians and civil servants are interdependent and mutually influence each other. By arguing that complementarity captures the nature of political-administrative relationships, Svara ( 2006a, 2006b) supplanted the traditional view, in which the relationships between politicians and administrators are marked by separate and dichotomous roles. Overeem ( 2005, 2006) has argued that most contemporary scholars deem the dichotomy to be outdated, as it appears inappropriate for understanding the current configurations of the politics-administration continuum. While doing so, however, they blur the boundary surrounding politics, he contends. This increases the risk of losing sight of the point where civil servants are drawn into partisan politics. Reflecting on the same topic, Aberbach and Rockman ( 2006) have argued that the increased influence of experts and civil servants in policy-making has become more common since the 1980s, but also heavily criticized. Rather than overlapping roles, civil servants have continued to bring facts and expertise to the policy-making process, while politicians still tend to absorb values and represent interests in society.

This very much echoes Wildavsky's ( 1979) frequently quoted idea that civil servants, who work with policy development and implementation, should 'speak truth to power'. But the ability for planners to engage in and mobilize fearless speech, or parrhesia, has become more limited. Grange ( 2017) has recently argued, for example, that Swedish local planners have become under pressure to conform and be loyal to current neoliberal politics. Lack of critical discussions and expressions of resistance have also been reported in other local government contexts (e.g. Paulsson, 2014). Although the relationships between politicians and civil servants continue to be marked by the institutionalized expectations on their respective roles, civil servants are increasingly being pressured to align with political ideas and ideals that go counter to their professional ethos (Grange, 2017). Opposed to this is the trend where 'inside activists', i.e. politically enlightened civil servants advocate and implement policies in the fields of sustainability and human rights (Briscoe & Gupta, 2016; Hysing & Olsson, 2011; Olsson, 2009; Olsson & Hysing, 2012).

Moving beyond the relationships between politicians and civil servants, there is a substantial literature on the role and function of the latter group. Civil servants can serve many roles and functions. He or she can either be a tool for the politician, or an ombudsman for the citizen or client. A third role is the role of the civil servant as a power broker, who takes part in shaping policies and decision-making processes. A fourth role is the knowledge-expert who builds society (Lundquist, 1998). Drawing upon the rich literature in planning studies (e.g. Healey, 2010), I suggest that collaboration is an appropriate concept to describe the multifaceted character of contemporary political-administrative relationships.

Collaboration has been proposed as a solution to the problems associated with the lack of democratic influence on urban developments (Healey, 2010) or as a device for public sector organizations to harnessing the private sector's capital, knowledge and skills (Emerson, Nabatchi, & Balogh, 2012). Collaboration, moreover, suggests that the silo-mentality often attributed to public sector bureaucracies comes with a host of problems and challenges related to capacity building. Yet, collaboration is also a time-consuming process and as an official policy, it risks adding a new layer of bureaucracy on to public sector organizations (Pell, 2016).

Here, collaboration is primarily understood as a space where relationships between politicians and civil servants evolve over time. A collaborative space is, thus, a space under continuous renegotiation, as well as a space that contributes to reproducing or producing new configurations of prevailing power and governance structures. Understanding the collaborative spaces in which translations occur is vital for understanding both how and where key concepts, in this case sustainability, are interpreted and defined in the translation process (Clarke et al., 2015; Healey, 2013).

The translation of policy

The debates about political-administrative relationships have many interesting insights to offer, but it is the intricate relationships between politicians and civil servants, or more precisely, the collaborative spaces where they meet and translate the concept of sustainability, that is of interest here.

Translation is here understood as the process in which a concept travels from one context to another (Clarke et al., 2015). It is neither an outcome that is inferior to an authentic or original meaning, nor entirely wrong or right, but a process where the outcome is to a varying degree meaningful (Freeman, 2009). Should the translation be as literal as possible, or should the task of the translator be to transfer the meaning of a body of text or a concept to a new audience are questions that have been debated for ages and different normative theories give different answers (see Buden, Nowotny, Simon, Bery, & Cronin, 2009). Yet, both approaches agree that meanings sometimes get 'lost in translation', e.g. when the translation process is too literal, or involves too much editing or deletion (Freeman, 2009). Translation should therefore be understood as a process placed both within and beyond language, imbued as it is with the taken-for-granted assumptions that give concepts and phenomenon meaning in a cohesive culture (Temple, 1997).

To understand why certain translations gain legitimacy while others do not, I want to return to Callon ( 1986) and his much-discussed study on the sociology of translation. He suggests that experts, professionals and laymen are 'locked into place' once the key issue for all involved actors has been established. These actors, then, gather support for their interpretation of the foreign practices and of the imported concepts from such diverse groups as consumers, other experts and scientific communities, as well as from colleagues and people in the industry. Based on this, the actors portray themselves as spokespersons for larger communities of people and thereby seek to gain legitimacy for their translation. Even though Callon does not employ the concept of a collaborative space, his study nonetheless vindicates the usefulness of this concept, as it provides a basic framework for understanding how translation processes are spaces imbued with negotiations, which are ultimately shaped by power relations.

In both policy (Clarke et al., 2015) and planning studies (Cook & Ward, 2012; Healey, 2012; Healey, 2013; Roy, 2011), investigations of translations as socio-technical processes have propagated recently. Rather than emphasizing the straightforward transfer or diffusion of policies, as they move from one context to another, Murray ( 2017, p. 152) has suggested, following Healey ( 2012, 2013), that 'it is more instructive to emphasize the translation (i.e. open to multiple interpretations) of these "travelling ideas" that assume hybrid "lives of their own" as they mutate and evolve under place-specific circumstances'. Although this interpretative approach enables a historical and contextual sensitization of the processes in which policy concepts and ideas are translated, I would add that these processes largely occur in, what I have termed, collaborative spaces.

In view of the purpose of the paper and the theoretical discussion above, I continue with a brief background on the governance of public transport in Stockholm, Sweden, which is followed by an analysis of how sustainability has been translated there from 2004 and onwards, as well as where, in which collaborative spaces, these translations have occurred and how these spaces have shaped the translation processes.

The governance of public transport in Stockholm, Sweden

The RPTA in Stockholm has seven organizational units. These units are clustered into two groups, each representing two spaces of public transport: the market space and the planning space. Whereas the market space is preoccupied with customer satisfaction as well as contract management and compliance, the planning space is preoccupied with long-term planning, strategic development as well as complying with policies, rules and laws. As will be explicated in the following chapters, these two sides not only have diverse and dissimilar informal relationships with the political level of the organization, they also translate sustainability differently. This, I argue, is due to the two different collaborative spaces where the concept is translated.

The market space of public transport: sustainability and the procurement of traffic

As in the rest of Europe, public transport in Stockholm has undergone several reforms that have involved the introduction of market mechanisms. Although no traffic is operated in-house anymore, the influence and the political control over operations have not diminished. By setting targets and deciding on larger investments and procurement contracts, politicians still exert influence and decide the strategic direction of public transport.

Environmental requirements and targets decided by politicians

The first comprehensive environmental policy was adopted by SL's politically instituted board only four days before Christmas Eve in 2004. It included goals on reducing the use of fossil fuels; reducing emissions of pollutants into the air; increasing the share of renewable resource; lowering the level of noise caused by its traffic; and so on. The environmental policy was originally developed by the staff working with environmental impact, but then re-examined by the politicians every two years and revised if necessary. In 2008, the environmental policy was transferred into a new template, while the content remained untouched compared to the previous version.

For the civil servants working on the so-called market side of the organization, translation was largely about developing environmental requirements to be used when procuring new traffic. When the fourth generation of the environmental policy was presented in April 2009, it included updates both in the policy itself and in the underlying principles, which then were to be translated by the civil servants into the new contracts that were to be developed (SLL, 2013a, 2013b). Due to SL being by far the largest procurer of public transport in the entire country, SL has been able to dictate the terms of the procurement contracts without meeting much explicit resistance (Bergström & Khan, 2007, p. 18). Although the RPTA no longer produced these services in-house, they ensured that the operators fulfilled the environmental requirements as specified in the procurement contracts, including the requirement to comply with ISO 14001: 2004, by closely monitoring and controlling their performance. This led the then CEO to proclaim that SL was Stockholm's largest 'environmental movement' (SL, 2009, p. 3).

In 2011, SL met or even surpassed the environmental requirements decided by the politicians in the County Council for the period 2007-2011. For example, the goal of having at least 50% of the buses powered by renewable fuels turned out to be 58%.¹ Another goal was to reduce nitrogen oxide emissions from the buses by 15%, but the outcome was 22%. A third goal was to reduce emissions of pollution particles from the buses by 25%, but in practice, it was reduced by 46% (SL Press release, 2012).

The same year, a new environmental policy for the entire Stockholm County Council was presented for the period 2012-2016 (SLL, 2011a). Civil servants from SL went through the proposal and devoted special attention to the parts that touched SL's operations and business model. The interim target of 75% renewable fuel in transport was considered to have the greatest impact on SL's operations. Raising the target from 50% to 75% would result in additional costs of about 15 million/year, which was considered both feasible and economically reasonable by the politicians in the County Council (SLL, 2011b).

Emerging here is the prevalence of quantitative measurements to manage public transport performance and evaluate its environmental impact. This is also reflected in the collaborative spaces where politicians and civil servants meet to exchange ideas and documents, but also where they decide on how sustainability should be translated. The more market mechanisms introduced, the broader the definition of sustainability. One example of this is how sustainability was broadened to include social aspects.

The emergence of social sustainability

SL signed UN's Global Compact in 2009. Global Compact contains guidelines and requirements for companies wanting to take social and environmental responsibility for achieving sustainable development. Global Compact includes principles regarding human rights, labour, environment and corruption (SLL, 2015). In addition to Global Compact, SL had to comply with the County Council's endorsement and interpretation of UN's Convention on the Rights of Persons with Disabilities and contribute to the County Council's goal of achieving its public health objectives (SLL, 2013b, p. 15).

When the newly instituted RPTA presented its first Regional Traffic Supply Program in 2012, sustainability stood in focus. The overall theme of this strategic document was: 'Attractive and sustainable transport system - goals for public transport' (SLL, 2012). The Vice-Head of the Department of Strategic Development told us that 'attractive travel' was supposed to imply a modal shift, where car owners leave their car in the garage at home and instead use public transport.

Figure 1 shows the RPTA's Target Model, which is the performance management model used to evaluate how well the entire organization lives up to its vision. The Target Model had some shortcomings though, the RPTA acknowledged in the Regional Traffic Supply Program. Social sustainability, including equality and equity, was mentioned in the Regional Traffic Supply Program but not included in the Target Model. The politicians were not too happy about this, so for the second edition, this had to be included, we were told by a senior strategic planner. Similarly, economic sustainability was only briefly mentioned in the first edition, but this was also to be included in the revised, second edition. Even though Global Compact had been part of the organization since 2009, this was not visible in the Target Model either. But work on this was under way in 2012, the RPTA stated in the first Regional Traffic Supply Program (SLL, 2012, p. 17).

Ecological sustainability was still much in focus, but social sustainability emerged as a recurring theme throughout the Regional Traffic Supply Program. For the RPTA, social sustainability meant that 'different social groups and their socio-economic conditions and needs of public transport' had to be considered (SLL, 2012, s. 10). This was crucial for public transport was supposed to contribute to greater equity and equality in the region, the politicians in the County Council had decided. But social sustainability, the way the RPTA expressed it, echoed the discourse of (corporate) social responsibility, which was not very surprising, given that Global Compact was already adopted in the organization. This resulted in the following general statement in the Regional Traffic Supply Program: 'all people should have equal rights and opportunities regardless of, e.g. ethnicity, faith, sexual orientation, opinion or disability' (SLL, 2012, s. 10). But the real challenge was to translate this stated ambition into measurable targets and to map the development of them over time under the rubric of social sustainability, I and my college were told by one senior planner.

While the first Regional Traffic Supply Program was a product of the civil servants' work, it was the politicians in the Traffic Board who set up the instructions, commented on draft versions and ultimately decided on its implementation. The policy process was subject to continuous discussions and balancing of various objectives, several interviewees explained. Some of the conflicting objectives and targets were also explicitly discussed in the Regional Traffic Supply Program, e.g. that the goal of cost efficiency may conflict with attractive public transport (SLL, 2012, p. 21). The task of balancing conflicting goals and prioritizing between different targets, though, was part of the political process, the RPTA stated explicitly in the Regional Traffic Supply Program (SLL, 2012, p. 21).

Developing a strategy for sustainable development

Unsatisfied with the lack of targets on social sustainability, the politicians instructed the civil servants to develop and come up with specific goals for social sustainability, one strategic planner explained (see also SLL, 2013a, 2013b). In March 2013, the result of this work was presented by the sustainability manager, along with senior staff in the Department of Strategic Development, in a strategic policy document called The Strategy for Sustainable Development. This document began by stating that it is not enough that public transport is more sustainable compared to other modes of motorized transport, but public transport must also 'be developed in a way that is viable from the three sustainability perspectives: environmental and social and economic' (SLL, 2013b, p. 2). The collaborative space in which this strategy developed was made up of cooperative and sympathetic relationships between the politicians in the Traffic Board and the group of civil servants in the unit of Sustainable Development. As these relationships were largely mediated through the production and circulation of documents, it was by examining these documents, it became possible to trace the relationships that made up this collaborative space. Eight principles were to guide the work towards sustainable development. Each of the principles was also explained in detail in terms of (i) what it meant, (ii) why it was included and (iii) how it would be realized. In addition to the environmental principles - which included use of renewable fuels, reduced noise, recyclable materials in new construction and so on - a definition and measurements of social sustainability were included for the first time. The RPTA, the document stated, would work systematically for achieving 'social responsibility in accordance with international conventions' (SLL, 2013b, p. 2) Social responsibility can include, for example, (i) not employing or benefitting from child or forced labour; (ii) non-discrimination; (iii) work against corruption; (iv)) fair wages and working hours; (v) freedom of association and (vi) ensuring health and safety (SLL, 2013b). To ensure that 'the fundamental human rights and working conditions are met' in the production of goods and services, SLL [the RPTA] should monitor and secure compliance among its pool of procured operators. While working on a new and updated version of the Regional Traffic Supply Program, where the Strategy for Sustainable Development would be an integrated part, the RPTA also updated its website with the following definition: 'Social sustainability is the goal, ecology sets the framework, while the economy is a means and a prerequisite for sustainable development' (SLL, 2017).

In sum, procurement and contract compliance is an important part of the RPTA's operations. While procurement has a time frame that usually ranges between 5 plus 5 years, physical planning and infrastructure projects work with a time frame that stretches much further ahead into the future, for they are both capital-intensive and difficult to undo once in place. As will be explained further below, this has meant that the market space and the planning space render different translations.

The planning space of public transport: integrating transport and land-use development

In Sweden, the municipalities are the sole land-use authority and they decide on the design of streets as well as on new areas for housing development. Integrating land-use and public transport constitute one of the main challenges for enabling sustainable transport, according to our interviewees. The civil servants in the Department of Strategic Development carry out a wide array of work tasks, including meeting representatives from the municipalities to discuss long-term planning as well as specific projects. Rather than having tough and challenging meetings, where everyone sits down to discuss the challenges with the long-term planning, and possibly face the risk of conflict, these meetings were often couched to be pleasant and not supposed to lead to, or involve, heated debates, explained one planner. For sustainability to be achieved, however, tough decisions that implicate trade-offs are unavoidable, he added. The challenge with multi-level collaboration, as between the RPTA and the municipalities, continued the same planner, is that 'we always must trust that our counterpart understands what is best for them, but there are situations where they do not'. When this is not the case, collaboration becomes a challenge, as mutual understanding becomes difficult to achieve, he concluded. Emerging here is a picture where the collaborative space is crucial in and of itself and for maintaining a positive atmosphere, while tough negotiations, which potentially could lead to improved outcomes in terms of sustainability, are avoided.

Organizing the measurements, locating the data sources

Sustainability remains a key issue and a boundary concept, around which actors gather to deliberate and discuss different courses of actions. Despite being a household concept, sustainability is elusive, unless it is broken down into smaller components and measured accordingly (Lyytimäki et al., 2013). This view was reflected by many of those being interviewed and by the fact that the responsibility for measuring sustainability was divided among three civil servants; one working on mainly environmental issues, another on social issues and a third on economic issues. The civil servant working on environmental issues had the responsibility to gather data on levels of noise, use of bio and fossil fuels, levels of emissions and so on. Other civil servants, working with measuring social sustainability, gathered data on accessibility, as well as data on public health and elderly transportation services. A third civil servant was responsible for keeping track of the economic impacts of public transport on society at large, e.g. by providing data on crowding on busses and trains, as well as data on traffic congestion. Thus, the task to measure sustainability was organized and entrusted to three persons. The politicians and the civil servants in the top-management team used these data to assess how well the RPTA as a whole managed to fulfil its objectives in The Target Model.

One planner reverberated the claim that sustainability is an ambiguous concept to which everyone has their own definition, but she qualified this claim by adding that this ambiguity also has implications for the funding of public transport. Although a bit long, her quote on this matter is well formulated and therefore worth including in its entirety.

Quarrelling about whose resources will be used is meaningless when those resources come from the same source would be a fair summary of her main argument. Yet, within each organization, those resources are understood as scarce as they come from either the County Council's or the municipalities' budgets, which both are limited. What this boils down to, the same planner explained, are priorities. Even though all strategic documents and plans contain the same set of keywords, priorities must be made for policy and planning to move forward in a sustainable manner, and politicians are far from being involved in this on a regular basis.

Returning to the first version of the Regional Traffic Supply Program, the Vice-Head of the Department of Strategic Development told us that some of the objectives in the Target Model had been recycled from previous strategic documents. What is new, and substantially so, he told us, was the targets to increase the market share for public transport of all motorized transport and the speeding up of travel time. To achieve this, traffic signals that prioritize busses and trams, as well as right-of-way lanes, are necessary. These initiatives, he suggested, require collaboration with municipalities about land-use and urban development. But as much as these targets are related to the long-term planning of public transport and the collaboration between the RPTA and the municipalities, they are also connected to the procured traffic operators' way of operating the buses and to traffic congestion, which, once again, are contingent on the integration of transport and land-use planning.

Conflicting goals in planning

When developing public transport, priorities are most difficult to agree upon when it comes to the questions of how land will be used, and at what cost. Several planners mentioned this in various ways. As concepts are translated and edited according to local configurations, sustainability means different things to different groups of people. Sustainable public transport is no exception. For example, in the plan to develop the Southern Tramway, a large-scale project to the South and South-West of Stockholm, sustainable public transport meant at least two different things. On the one hand, it meant that the tramway should run on separate embankments to speed up travel time and to make public transport an attractive option for car drivers. This translation was most clearly expressed in the statements by the RPTA. On the other hand, sustainable public transport also meant that the tramway should mix with other modes of urban traffic, to calm down car traffic and create a more urban streetscape. This translation was vibrantly expressed by the municipalities through which the tramway would run.

Conflicts also emerge because incommensurable objectives are embedded in the different laws and in political objectives (e.g. de Roo, 2000). It is in this intricate policy landscape and legislation that the RPTA not only procure traffic, but also develop understandings of sustainability in its planning space. Besides the formal changes coming with the new law in 2012, public transport in Stockholm has undergone other changes, epistemic ones, as well. From being understood and treated 'as some sort of welfare for people who did not have the sense to buy a car, public transport is now seen as a precondition for survival and growth', explained one planner. This has meant, he added, that public transport policy and planning has become much more interesting and important for the politicians, 'and this is also why public transport is understood as a tool by the politicians', he clarified, before continuing with retelling the history of political-administrative relationships in the public transport authority in Stockholm.

Understanding the connections between how and where sustainability is translated

Emerging from the interviews is a picture where there are plenty of discussions and collaborations between the politicians in the County Council's Traffic Board and the planners and managers in the RPTA. From what I could understand, these discussions orbited around the question what needs to be done to achieve sustainable transport.

As has been suggested here, procurement and planning are two collaborative spaces in which sustainability is translated. Whereas the former involves setting up requirements when designing contracts and ensuring compliance, the latter is not based on refined contracts, but on mutual understanding between the planners in the RPTA and the planners in the municipalities. Whereas environmental and social requirements on operators can be specified in the designing of contracts, the integration of land-use and transport planning is a much more ambiguous undertaking, as this cannot be broken down into measurable targets. This also has implications for how politicians and civil servants collaborate and how sustainability is translated in the RPTA.

The relationships between (A) the politicians and (B) the civil servants, as well as the relationships between (B) the civil servants, on the one hand, and (C) the traffic operators and the municipalities, on the other hand, can schematically be described as follows.

Figure 2 displays the collaborative space on the market side of the authority, where (A) the politicians in the County Council's Traffic Board formally set targets and decide on goals for (C) the procured traffic (including fuels, emissions, polluting particles, etc.). And this is done with the aid of (B1) the civil servants and their knowledge about measurements and data sources, while (B2) another group of civil servant's design contracts and ensure compliance of (C) the procured traffic. The civil servants are here taking a role as knowledge brokers, as they are intermediaries that develop relationships and facilitate translations, while also bringing their own knowledge and expertise to the extended relationships (Lundquist, 1998).

Figure 3 shows the collaborative space on the planning side of the authority, where (A) the politicians in the County Council formally set targets and decide on goals for the long-term planning, which is contingent on multi-level collaborations, primarily with (C) the planners and civil servants in municipalities. But it is (B) the civil servants (strategic planners) in the RPTA who manage and maintain the collaborative spaces with (C) the planners in the municipalities. Here, the civil servants take on the roles of an ombudsman (Lundquist, 1998), or even an inside activist (Olsson & Hysing, 2012), as they contribute to translating the ambiguous concept of sustainability onto the extended relationships with the municipalities.

The two collaborative spaces render different relationships, which further lead to various types of translations of sustainability. In the market space, the politicians govern at a distance by way of setting quantitative and measurable targets for the traffic operators, rendering the civil servants as intermediaries or knowledge brokers in the translation process (Lundquist, 1998). Sustainability is not only confined to quantitative environmental requirements transferred to operators by contract; it has also broadened over the years. Beginning in 2009, social responsibility formally entered the organization through the adoption of Global Compact, and in 2012, with the first Regional Transport Supply Program, social sustainability was mentioned but not defined in the Target Model. The politicians instructed the civil servants to produce measurable targets also for social sustainability; otherwise, it would be difficult to measure the overall progress towards sustainability both ecologically and socially. While this might suggest that the civil servants were a tool for the politicians, the civil servants were in fact providing the politicians with the knowledge about the measurability of targets and so limiting the scope of interpretation of sustainability.

In the planning space, the planners are rendered as more than intermediates, for they are creating the opportunities and imaginaries that the politicians must consider when deciding on the trajectory of long-term planning. How public transport should be integrated in the urban environment is largely beyond the influence of the politicians, as this is primarily a qualitative undertaking, contingent on the urban landscape and land use. The politicians do have comments on this, obviously, and ultimately also decide on budgetary constraints for specific projects and for planning. As indicated above, however, it is the planners from the RPTA who meet the planners from the municipalities and discuss and subsequently translate sustainable transport into specific projects (e.g. the Southern Tramway). As the civil servants are acting as an ombudsman and occasionally as an inside activist (Hysing & Olsson, 2011), sustainability is translated as the remaking of urban spatial development with the target to increase the modal share of public transport. Unlike the market side of the public transport, where the translation of sustainability follows quantitative measurements, the integration of transport and land use is difficult to measure, let alone evaluate for the politicians, in quantitative terms. But the modal share of public transport works as a proxy for measuring sustainable transport.

Conclusions

This paper has contributed to the understanding of sustainability in general and sustainable transport in particular by investigating how and where this overarching policy has been translated in the context of public transport. By drawing upon the literature on policy translation and political-administrative relationships, an innovative framework was developed around the concept of collaborative spaces. This framework was applied to analyse the how and where sustainable transport was translated in the political-administrative nexus in the RPTA in Stockholm.

Two main conclusions were identified, one related to the question how sustainability has been translated, and another related to the question where, in which collaborative spaces, this has occurred.

Firstly, over the years, sustainability has expanded to include not only ecological concerns, but also social and economic ones. Environmental sustainability has been around since the late 1980s in public transport in Stockholm, when biofuels started to replace fossil fuels. Although the first environmental policy was not presented until 2004, policies pertaining to environmental sustainability had been part of other policies and guidelines. Environmental sustainability was surrounded by a high degree of political consensus, for it has historically been translated as a policy that seeks to increase the modal share of travel by public transport. Environmental sustainability has also been standardized and transferred to the private traffic operators via the civil servants' design of contracts and monitoring of compliance. Environmental sustainable transport was translated into measurements of biofuels, emissions, noise and so on, and so mechanically reproduced from the politicians via the civil servants to the private operators. Following the previously discussed theories of translation, this was a translation process that involved little room for interpretation for the receiving organization. However, in 2009, social sustainability entered Storstockholms lokaltrafik when it decided to adopt UN's Global Compact. This is how the discourse of (corporate) social responsibility entered the organization, a discourse that has become ever more present during the past few years. Yet, socially sustainable transport remains open to a wide range of interpretations, which is why the politicians demanded the civil servants to develop new measurements.

Secondly, sustainability has been translated in two distinct ways in two different spaces of the RPTA. In the market space, the politicians have primarily governed at a distance by setting measurable goals and targets for the procured traffic, and left the designing of contracts and the task of ensuring compliance to the civil servants. Thus, the collaborative space was shaped by what I term quantized relationships. This is because the quantitative measures used to translate sustainability from policy to operations further shaped the relationships between the politicians and the civil servants insofar as the latter were cast as intermediaries or knowledge brokers between the politically set goals and targets, on the one hand, and the private traffic operators, on the other hand. In the planning space, the politicians have generally been preoccupied with administering the budget and deciding on major investments, while the civil servants have been responsible for making sense of and figuring out ways to measure sustainable transport and lately social sustainable development. Yet, sustainability measurements have been hard to quantify when it comes to integrating transport and land-use planning. This was solved in an organic manner, in specific projects, between the strategic transport planners in the RPTA and planners in the municipalities.

These two main conclusions are of relevance to previous studies as they show that policy translation is far from a straightforward process inside the translating organization. Rather, the policy translation process and its outcomes are contingent on the collaborative spaces between the politicians and the civil servants, and their relationships to their respective group of stakeholders. Unlike previous studies investigating policy translation processes in the context of urban development, like Business Improvement Districts (Cook & Ward, 2012; Peyroux, Pütz, & Glasze, 2012) or Buss Rapid Transit (Montero, 2017; Wood, 2014, 2015a), this study has contributed with new knowledge of how and where an empty signifier, in this case sustainability, has been translated. How sustainability is supposed to be achieved in a context that is comparatively already sustainable is, thus, contingent on how it is interpreted and defined - i.e. translated - which, again, is a shaped by where, in which collaborative spaces, this occurs.

Acknowledgements

I would like to offer my special thanks to Karolina Isaksson, Claus Hedegaard Sørensen, Tom Rye, Christina Lindkvist Scholten and Robert Hrejla for their valuable comments and constructive criticisms on earlier versions of this paper.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Additional information

Funding

Financial support was provided by VINNOVA [grant number 2013-03020] and K2, The Swedish Knowledge Centre for Public Transport.

1 Previously, SL bought and owned most of the buses in regular service, while private traffic operators leased them as part of the procurement contract. Nowadays, bus operators increasingly own the buses, but there is still a mixture of owning and leasing, depending on the procurement contract.

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Making the sustainable more sustainable: public transport and the collaborative spaces of policy translation

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ABSTRACT ABSTRACT This paper investigates where and how sustainable transport goals are translated into public transport planning and operations. The case where this is explored is the Regional Public Transport Authority (RPTA) in Stockholm, Sweden. By drawing upon recent discussions on policy translation and political-administrative relationships, sustainable transport is found to be translated in two different collaborative spaces in the RTPA.

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Highlights

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The overview of existing work on smart (and) sustainable cities is comprehensive, thorough, topical, and original.

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Several critical issues remain unsettled, less explored, largely ignored, and theoretically underdeveloped for applied purposes.

*

Numerous research opportunities are available and worth exploring, as the field of smart sustainable cities is still in its early stages of development.

*

One opportunity of high relevance and importance is to develop a theoretically and practically convincing model of smart sustainable urban form or a framework for strategic smart sustainable urban development.

*

This holistic approach is believed to be the first of its kind and hence has not been, to the best of one's knowledge, produced elsewhere.

Abstract

In recent years, the concept of smart sustainable cities has come to the fore. And it is rapidly gaining momentum and worldwide attention as a promising response to the challenge of urban sustainability. This pertains particularly to ecologically and technologically advanced nations. This paper provides a comprehensive overview of the field of smart (and) sustainable cities in terms of its underlying foundations and assumptions, state-of-the art research and development, research opportunities and horizons, emerging scientific and technological trends, and future planning practices. As to the design strategy, the paper reviews existing sustainable city models and smart city approaches. Their strengths and weaknesses are discussed with particular emphasis being placed on the extent to which the former contributes to the goals of sustainable development and whether the latter incorporates these goals. To identify the related challenges, those models and approaches are evaluated and compared against each other in line with the notion of sustainability. The gaps in the research within the field of smart sustainable cities are identified in accordance with and beyond the research being proposed. As a result, an integrated approach is proposed based on an applied theoretical perspective to align the existing problems and solutions identification for future practices in the area of smart sustainable urban planning and development. As to the findings, the paper shows that critical issues remain unsettled, less explored, largely ignored, and theoretically underdeveloped for applied purposes concerning existing models of sustainable urban form as to their contribution to sustainability, among other things. It also reveals that numerous research opportunities are available and can be realized in the realm of smart sustainable cities. Our perspective on the topic in this regard is to develop a theoretically and practically convincing model of smart sustainable city or a framework for strategic smart sustainable urban development. This model or framework aims to address the key limitations, uncertainties, paradoxes, and fallacies pertaining to existing models of sustainable urban form-with support of ICT of the new wave of computing and the underlying big data and context-aware computing technologies and their advanced applications. We conclude that the applied theoretical inquiry into smart sustainable cities of the future is deemed of high pertinence and importance-given that the research in the field is still in its early stages, and that the subject matter draws upon contemporary and influential theories with practical applications. The comprehensive overview of and critique on existing work on smart (and) sustainable cities provide a valuable and seminal reference for researchers and practitioners in related research communities and the necessary material to inform these communities of the latest developments in the area of smart sustainable urban planning and development. In addition, the proposed holistic approach is believed to be the first of its kind. That is, it has not been, to the best of one's knowledge, investigated or produced elsewhere.

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Smart sustainable cities of the future: An extensive interdisciplinary literature review

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The overview of existing work on smart (and) sustainable cities is comprehensive, thorough, topical, and original. * Several critical issues remain unsettled, less explored, largely ignored, and theoretically underdeveloped for applied purposes. * Numerous research opportunities are available and worth exploring, as the field of smart sustainable cities is still in its early stages of development.

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This paper presents a concepualisation of the research and practice challenges facing those of us working towards sustainable cities. I argue that these challenges are quite fundamental and centre around our 'vision' of the sustainable city and the processes required to bring about sustainable urban development. I draw on my own experience and the work of others to suggest that within the sustainable cities discourse there are a number of competing 'visions' of sustainable urbanism, and that it is important that we understand and value this multiplicity of socially-constructed potential futures, rather than adopt a 'one model fits all' appraoch. In terms of sustainable urban development processes, I suggest that research, practise and expertise tend to coalesce around either scientific and technological advances or around social change (largely couched in terms of behaviour, economic or governance shifts). Yet we need to move past this dualistic thinking towards a far deeper understanding of the interplay between social and technical solutions if we are make real progress. I hope this new journal provides a forum to explore different 'visions' and to share knowledge on the 'mulitple-pathways' that sustainable urban development may take.

1. Introduction

... the city is rooted in the habits and customs of the people who inhabit it. The consequence is that the city possesses a moral as well as a physical organization, and these two mutually interact in characteristic ways to mold (sic) and modify one another. (Park , p. 578)

At the beginning of a new decade we have the opportunity to look forward and consider what we could achieve in the coming years. With reference to Park's quotation above, we have the chance to consider the desired future of both the 'moral and physical organisation' of the city. The start of 2010 also marks the beginning of this new International Journal of Urban Sustainable Development, which invites us to think about how the subject of 'sustainable urbanism' might develop and about the debates that authors may want to contribute to in the coming issues.

I have been invited to write in this first issue about the research and practice challenges facing those of us working towards sustainable cities. This is a call that requires both reflection on what has been achieved in the 30 years or so that 'sustainable cities' have been the leading global paradigm of urban development (Whitehead ) and to venture some thoughts about where it might be useful to channel our efforts now and in the future.

I have identified two key challenges, drawn from my experiences of working on sustainable urbanism research projects, policies and monitoring strategies. The challenges are quite fundamental. They are the challenge of 'the vision': do we know what 'the sustainable city' is? and the challenge of change: do we know how to bring about 'sustainable urban development'? In addressing these challenges, I am also citing other scholars and practitioners whose perceptive thoughts I have returned to time and again and are highly relevant now. Of course, the challenges I identify are not exhaustive, but I am setting out some ideas that others may want to add to refine or refute: hopefully in the pages of this Journal.

2. Sustainable cities and sustainable urban development

The subject of 'sustainable cities' is endlessly fascinating. There are now global and local commitments to make urban areas into 'sustainable cities' through various processes of 'sustainable urban development'. Numerous actors are involved in the academic and practical aspects of the endeavour. We see, for example, social scientists, built and natural environment specialists, engineers and artists all undertaking research, and developing strategies and programmes, to tackle elements of sustainable urbanism.

Yet knowing if we are actually making any progress towards sustainable cities is problematic. In one sense, so much has been achieved in raising the profile of sustainability and sustainable cities over the last 30 years that the rate of change is inspiring. Urban policies around the world are infused with the language of sustainability and a multitude of exemplary initiatives can be found. Yet, in other ways, we seem to be going backwards, to the extent that it is hard to see where there is any room for optimism. Urban problems in developing countries are becoming more acute as populations rise and resources become scarcer. In the developed world, we see massive new infrastructure and building projects that defy any notion of sustainability, yet are celebrated by the public and professionals. So, although there have been huge advances in some areas of knowledge, and some impressive practical initiatives, a very contradictory, or at least fragmented, picture arises of change 'on the ground'.

Given this complex picture, it is sometimes hard to see where common 'sustainable cities'' challenges may be identified. However, part of the problem in conceptualising progress centres is around what we think we are aspiring to, what changes we want to make and what we assess 'progress' to be. It is this conceptualisation of sustainable cities that lies at the heart of the challenges I set out below.

3. The challenge of 'the vision': do we know what 'the sustainable city' is?

Despite the fact that the 'sustainable city' discourse is now relatively mature, precise conceptualisations are rare and contested. As Bulkeley and Betsill state, 'Despite ... near universal recognition that sustainable cities ... are a desirable policy goal, there is less certainty about what this might mean in practice' (2005, p. 42). We find the notion of the sustainable city immediately appealing, yet complex and intangible.

In reality, most disciplines working in the field of sustainable cities construct their own notion of what the concept means for them. We see 'ideal states' proliferate in many sectors. For example, in engineering, the sustainable city is defined when resources are used most efficiently. Systems are mapped and losses and uncertainties identified. In the social sciences, sustainable cities are often described in terms of the goal of 'social sustainability'. It is the desired 'ideal', realised only when a particular conceptualisation of social equity or justice is evident in a spatial setting. Within the 'sustainable urban form' debate, the idea of the 'compact city' has been favoured, above other settlement patterns in policy for a number of decades (although with less agreement by researchers in the field, (Williams et al. ). Yet these 'ideals', and the debates about them, remain within their discrete worlds and are rarely acknowledged or understood outside their expert communities.

The issue here is that all interest sectors involved in achieving sustainable urban development have genuine but differing 'visions' of the future. As Guy and Marvin state '... within the sustainable-cities debate, a diverse and expanded group of interests can be identified, each developing competing visions of what a sustainable city might become' (1999, p. 269). None of these 'visions' represent the complete picture (although some claim to), as each is only a part of the complex 'whole' that is the city.

I have long agreed with Guy and Marvin that understanding this multiplicity of socially constructed visions (or 'pathways') of sustainable urbanism is at the core of advancing research and practice. It seems sensible to assume, for example, that the 'pathways' towards sustainability for Nairobi will be very different than those for Paris. However, it has been interesting to witness how many culturally and geographically specific ideas have been replicated across the world, with little consideration or investigation of their appropriateness (see, e.g. Williams ( for a discussion of the transferability of the 'compact city' model in developing countries). I also agree with Guy and Marvin's assertion that '... the role of research is to keep alive a multiplicity of pathways by opening a wider discourse and dialogue about the types of future we might be able to create' (1999, p. 273).

This said, we do also need to recognise that these multiple pathways need some coherence of purpose, otherwise the much reported 'conflicts and contradictions' within sustainable urbanism thinking and practice will continue with no conceptual 'anchor'. Here the generally agreed principles at the heart of sustainability discourse, the prudent use of environmental resources and inter- and intra-generational equity still serve us well. However, as we all know, understanding and operationalising these concepts over different temporal and spatial frames are complex and political matters that will, no doubt, be the focus of much debate over the next decade.

4. The challenge of change: do we know how to bring about 'sustainable urban development'?

If we understand and respect that there are multiple visions of 'the sustainable city', and indeed multiple pathways to achieving it, then we need to accept that 'making' our cities more sustainable (through sustainable urban development processes) will be dependent on a similarly wide-ranging selection of actions. Some actions will be 'top-down' and require strong leadership and, perhaps, large-scale investment programmes; other changes may be bottom-up and rely on, for example, shifts in behaviour. These changes shift in prominence in any given place and will happen at different paces (some over weeks, some decades) and at different spatial scales (e.g. the home, street, neighbourhood, city and city region).

This multi-faceted conceptualisation may also help us 'place' our activities when striving to bring about urban change. At present the range of actions focussed on achieving sustainable urban development is often characterised as being split between 'technical' and 'social'. Research, practice and expertise tend to coalesce either around the scientific and technological advances that need to be made or around social change, largely couched in terms of behaviour, economic or governance shifts. These two spheres of action (technical and social) are often seen as separate and opposing. For example, Bulkeley and Betsill argue that 'This propensity for analyses of urban sustainability to focus on technocratic models and wish-lists of measures which should be introduced ... has meant that critical questions concerning the political struggles which take place in defining what urban sustainability might entail have been neglected' (2005, p. 43). They are suggesting that it is the concentration on technical issues that is responsible for an absence of a political debate. We also see engineers and scientists criticised for not understanding how their technologies fit with urban policy or not grasping if and how they will be taken up by end-users.

I suggest that the challenge for the next decade is to move genuinely past this dualistic thinking. We will not make much progress in sustainable urban development with an 'either/or' approach. The huge urban challenges we face, in areas such as climate change, energy, poverty, health, housing and transport, require an integrated approach. We need to continue to advance our understanding of technical and social change. However, we also need a much stronger evidence base around the 'intersections' of social and technical knowledge and practice. We need to understand how social contexts and processes can enable the development and use of sustainable technologies and how technologies can shape and educate us. Guy and Marvin conceptualise a research challenge as being to 'map the multiple constructions of the sustainable city, to understand the changing social contexts that produce them, and to build an understanding of the multiple logics emerging to re-order social relations, resources flows and urban form' (1999, p. 272). To achieve this requires both a deepening of specialised knowledge in some areas, a respect for, and understanding of different research approaches and traditions and some genuinely new ways of working. It also requires different partnerships and coalitions, perhaps between scientists, social scientists, politicians and the public; and it requires open minds.

Of course, many people are working in this way already. We are seeing a growth in inter-, multi- and trans-disciplinary research and practice. It was interesting to see that the outcome of a recent Symposium in the United Kingdom to identify 'Sustainable Urban Environment Grand Challenges' concluded that some of the major problems to address are socio-technical. The Symposium composed mainly of engineers and physical scientists, yet the key challenges included aspects of behaviour, policy and urban governance change. One of a number of the 'visions' that participants developed was that of 'A city where individuals, businesses and organisations can make the most sustainable choices and they are supported through technology, appropriate design of the physical environment, information and feedback' (EPSRC 2009). As a partial working vision this seems useful.

Hopefully, this multi-faceted view of sustainable cities will also enable us to be more aware and, perhaps, optimistic about the processes of 'sustainable urban development'. It may help us take on board that not all changes can be planned and managed and that some unforeseen outcomes may still lead us up desirable 'pathways'. This is particularly important in an era of globalisation, when even the best-laid plans can be incredibly difficult to implement. We have seen recently that, in developed countries, some of the most ambitious and interesting sustainable development projects (e.g. new eco-settlements and public transport infrastructure projects) have been abandoned or postponed as a result of the global economic crisis. However, the downturn has also allowed some smaller-scale, innovative schemes to be realised and has provided time for some developments to be improved in terms of their sustainability credentials. There has also been a renewed interest in community-based approaches to sustainable living and some significant pro-environment behaviour shifts, as people try to make limited resources go further. Of course, we do not know what the net effect of the crisis will be for the sustainability of urban areas; there will be winners and losers. But we can, at least, see opportunities within the crisis for maximising chances to move along desirable pathways in some cities.

5. Taking the challenges forward

I have highlighted what I see as two of the most interesting and critical challenges in sustainable urban development: understanding the 'vision' (or visions) and developing a deeper understanding of the multi-faceted processes of change required to achieve more sustainable cities. I have offered a conceptualisation of multiple pathways and processes (drawing on Guy and Marvin ) and have argued that a move to a deeper understanding of the interplay between social and technical solutions for sustainable cities is required. I hope that this journal provides a forum to explore 'visions' from a number of perspectives and to share knowledge on the multiple pathways that sustainable urban development may take. One of the Journal's main aims is to present multi-disciplinary work, and this is to be welcomed.

Park said, in , 'It is the structure of the city which impresses us by its visible vastness and complexity, but this structure has its basis, nevertheless, in human nature, of which it is an expression. On the other hand, this vast organization which has arisen in response to the needs of its inhabitants, once formed, impresses itself upon them, in turn, in accordance with the design and interests which it incorporates' (1915, p. 578). Let us hope that in the coming decades cities develop in response to their inhabitants' needs for a sustainable future and that, as Park suggests, the design and interests of sustainability are impressed upon the people too. It will be critical that we move towards a sustainable future through both the 'moral and physical organisation' of the city.

References

and 2005. Rethinking sustainable cities: muilti-level governance and the urban politics of climate change. Environmental politics, 14(1): 42-63.

[EPSRC] Engineering and Physical Sciences Research Council, 2009. Outputs from the sustainable urban environment programme grand challenge workshop, 14 and 15 July 2009. Swindon: EPSRC.

1915. The city: suggestions for the investigation of human behavior in the city environment. The American journal of sociology, 20(5): 577-612.

Whitehead, M. 2003. (Re)Analysing the sustainable city: nature, urbanism and the regulation of socio-environmental relations in the UK. Urban studies, 40(7): 1183-1206.

Williams, K., 2004. Can urban intensification contribute to sustainable cities? An international perspective. City matters [online]. Official Electronic Journal of Urbanicity, UN Habitat Partnership Initiative, Available from http://www.urbanicity.org (Accessed: ).

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Sustainable cities: research and practice challenges

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This paper presents a concepualisation of the research and practice challenges facing those of us working towards sustainable cities. I argue that these challenges are quite fundamental and centre around our 'vision' of the sustainable city and the processes required to bring about sustainable urban development.