In June 2003, SBS Transit Ltd began operations of the North East Line (NEL), a highly advanced fully automated underground heavy rail system that sets new engineering and technological benchmarks in mass transit systems. Built at a cost of S$5 billion, the NEL is 20km long and comprises 16 stations covering Punggol to HarbourFront.

It also operates the 42km Downtown Line (DTL), the longest underground line in Singapore with 34 stations. The first stage of DTL commenced passenger service on 22 December 2013, while the second stage of DTL commenced passenger service on 27 December 2015. It became fully operational on 21 October 2017.

SBS Transit also operates the Sengkang and Punggol Light Rapid Transit Systems.