The idea of constructing a rapid transit line in the country was initiated in 1967, when a four-year State and City Planning study conducted by the Singapore government and the United Nations Development Programme. It was part of an urban renewal and development project which aimed to formulate a long-term comprehensive concept plan for guiding the country's future physical development. It was concluded that physical land constraints faced by the island nation, was not able to accommodate more roads to meet the rise in transportation demands. It was noted that the city state needed a rail transit system by 1992.^[1]

It took 10 years since 1972 to design the MRT system, which continued all the way until the government gave permission to build the MRT.

In 1972, a team of consultants and professional officers seconded from the government embarked on a major transport study known as the Singapore Mass Transit Study. In phase one of the study, the team examined existing and future transport demands, analysed various options and made recommendations for government investment in public transportation. The team recommended the rail mass transit as the best option for meeting the anticipated travel demands of Singapore.

Phase two of the study, which commenced in 1975, examined the technical, economic and financial feasibility of the mass transit system. This study argued that a bus-rail system was a “superior alternative” to an all-bus system, with only a remote chance of a disastrous result.

Despite the study’s recommendation for the development of a MRT system, the high costs involved and the possible impact on patterns of land use and economic activities prevented the government from making an immediate decision. The issue was complicated by a review of the phase two study by a team from the World Bank. The World Bank team had issues with the Singapore team’s costing and assessment of the relative benefits of the bus-rail plan compared to an all-bus system.

Phase three of the study was conducted between 1979 and 1980, and provided a preliminary engineering design for the recommended transit system. In 1980, a Provisional Mass Rapid Transit Authority was appointed to undertake preparatory work for the construction of a possible MRT system.

Despite the findings of the mass transit studies, the government was still hesitant to commit to the MRT system. A team of foreign consultants (also known as the Harvard team) led by team leader Kenneth Hansen was engaged to review the previous mass transit and other transportation studies.

In their report, the Hansen team argued that the earlier studies were based on incorrect assumptions and thus failed to consider other approaches to solve Singapore’s transport problems. Rather than a MRT system, the Hansen team recommended a high performance all-bus system coupled with feeder routes and motorcar restraint. Even if Singapore were to develop a MRT system, the team suggested that only one line be built as they believed that this would be sufficient to relieve traffic congestion and allow the bus system to function.

When the late president Mr Ong Teng Cheong became the then-Minister for Communications (now the Ministry of Transport), he had to convince the cabinet in a debate in early 1980, that the S$ 5 billion needed for the system would be beneficial for the long-term development of Singapore. He argued that

Therefore, a provisional Mass Rapid Transit Authority was established in July 1980, after the debate. However, Mr Ong faced strong opposition from other members of the cabinet, by Finance Minister Goh Keng Swee and Tony Tan, due especially to the heavy investments involved. A team of specialists from Harvard University, recommended that an all-bus system would be sufficient into the 1990s, and would cost 50% less than a rail-based system.

Later on, two independent American transport and urban planning specialist teams were then appointed by the government to conduct their own independent reviews as part of the Comprehensive Traffic Study in 1981. This debate was also brought to national television in September 1980, which was rare at that time. The study came to a conclusion that an all-bus system would be inadequate as it would have to compete for road space which would have been increasingly overcrowded by then. The problem would be solved by building a rail system. Mr Ong hence declared in triumph on 28 May 1982, that

The permission to begin the construction of Singapore's then-largest public works project was given in May 1982. A ground-breaking ceremony commenced the construction on 22 October 1983 at Shan Road. The majority of the work was expected to be completed in 1992. This included 67 km of track to be constructed, with 42 stations, of which 26 would be elevated, 1 at grade and 15 underground. The network was constructed in stages, with the North South Line given priority as the line passed through the Orchard Road corridor as well as the rest of the Central Area, the latter of which faced a high demand for public transport. Also, it was near the more densely populated housing estates such as Toa Payohand Ang Mo Kio. The MRT Corporation, now Land Transport Authority, was established on 14 October 1983, taking over the roles and responsibilities of the former provisional Mass Rapid Transit Authority. On 6 August 1987, it set up SMRT Corporation.

Construction began in various areas:

Toa Payoh MRT Station was the first to do structural works, followed by the tunnels between Outram Park and Tiong Bahru in 1985. The completion of the viaduct for Phase 1 was done on 15 December 1986 at Commonwealth MRT Station. The first C151 train was delivered to MRT Corporation on 8 July 1986, by Yeo Ning Hong at Bishan Depot.

One third of the MRT was completed on 15 January 1985, and the Minister for Communications and Information Yeo Ning Hong visited Orchard MRT and Dhoby Ghaut MRT Station sites.^[2] The pouring of concrete was completed by the end of 1985 at Dhoby Ghaut MRT Station.

On 7 November 1987, the first 6 kilometres of the North South Line from Yio Chu Kang to Toa Payoh went into operation.^[3] The novelty resulted in thousands flocking to the 5 station segment of the line just to experience and try out the system. At the launching of Toa Payoh, the late Mr Ong was quoted as saying that

Nine more stations from Novena to Outram Park were officially opened 12 December 1987 by then Deputy Prime Minister Goh Chok Tong. These trains ran as a through service from one end to the other even though Tanjong Pagar and Outram Park were on the East West Line.

On 12 March 1988, with the opening of six more stations from Tiong Bahru to Clementi on the East West Line, City Hall and Raffles Place becoming interchange stations between the two lines. On the same day, the system was officially launched by the late Mr Lee Kuan Yew, then Prime Minister of Singapore.