Train services on the North-South Line (NSL) and Downtown Line (DTL) were delayed by two separate and unrelated faults this morning.  Engineers from the Land Transport Authority (LTA), SMRT and SBS Transit (SBST) were deployed immediately to identify the root causes of these faults. Regular train services on the NSL and DTL resumed by 9.15am and 9.00am respectively.

NSL Train Services

2.  Preliminary findings indicate that the fault may have been caused by a defective train transmitting erroneous signals to the Wayside Radio Units (WRUs)^[1] along the NSL. This caused the WRUs to fail, and trains had to move at a slower speed for safety reasons. Reduced train frequencies led to congestion at NSL stations. The defective train has since been pulled from service, and a team of engineers from LTA, SMRT and Thales, the supplier of the new signalling system, are conducting further investigations into the cause of the fault.

DTL Train Services

3.  Preliminary findings indicate that a fault in the DTL’s Automatic Train Supervision^[2] (ATS) system prevented trains from being automatically launched from the depot this morning.  Subsequent trains were then manually driven to the main line at a lower speed, leading to delays.  The fault has since been rectified and a team from LTA, SBST and Siemens, the supplier of the ATS system, is conducting further investigations into the cause of the fault.

Alternative Transport Options

4.  Free regular bus services, together with bridging bus services were made available to commuters  this morning along affected stretches of the NSL and DTL. Additional staff were also activated to assist commuters. The Singapore Examinations and Assessment Board (SEAB) was also alerted to the delays, and station staff were on hand to assist students heading to examination centres.

5.  We are sorry for the inconvenience commuters faced this morning. LTA continues to work closely with SMRT and SBST and both incidents will be thoroughly investigated.
 

^[1] A WRU, which is part of the Communications-Based Train Control (CBTC) signalling system, is used to transmit signals between trains and MRT stations.

^[2] The ATS ensures that train services operate according to a prescribed timetable.