East West Line
The East West Line and the North South Line utilized identical rolling stock up until the recent years, when the C151A was temporary suspended from operating on the North South Line between January 2012 and November 2013 following the 2011 Train Disruptions. The C151B, which was introduced in April 2017, did not begin revenue service on the full-stretch of the East West Line until the line's trial of the CBTC signalling system in May 2018.