although there were some c151bs housed in tuas depot since the inception of the tuas west extension, c151bs did not begin revenue service on the full-stretch of the east west line only until on 27 may 2018, when the line switched to the new signalling system. c151bs running on the ewl before that only ran on the tuas west extension, between gul circle and tuas link. only that section had the new signalling system installed. on 27 may 2018, all 45 c151b trains have entered service on the north south line and east west line.