SINGAPORE — Transport operator SMRT has warned commuters to be prepared for potential glitches on the North-South Line from next Monday (May 29), as it expands tests on a new signalling system to include weekdays.

The tests, which began in March, have been progressively expanded from the last hour of weekday services to Sundays, and to include more trains. The new weekday tests will involve the NSL's full fleet of 124 trains, though SMRT did not specify the exact date and time the latest checks will commence.

"During the weekday system checks, the new signalling system may continue to encounter some glitches as it settles in to full-load operations," the operator warned in a press release on Friday (May 26).

"Commuters on the NSL could experience instances of train and platform doors not opening or closing promptly, trains held at stations slightly longer than usual, or trains stopping momentarily between stations."

It added that during earlier rounds of the signalling tests, the safety system halted trains momentarily so that engineers could fix the signal glitches.

SMRT said this is a safety feature to ensure trains are kept at a "proper distance from one another at all times", adding: "Such situations are not safety critical and SMRT, the Land Transport Authority and (SMRT's contractor for the system) Thales will have more engineers on standby to respond quickly to situations that may arise. More station staff will also be on hand to assist commuters."

Mr Alvin Kek, SMRT senior vice president for rail operations, said: "We continue to ask for commuters' patience and co-operation as we work round the clock to settle the system in as quickly as possible."

The latest checks on the NSL - Singapore's oldest MRT line - are timed to coincide with the June holidays to minimise commuter inconvenience, and will eventually allow trains to operate at intervals of as short as 100 seconds, the train operator said.

The checks will also help to ensure more accurate train and station door alignment and coordination, familiarise train captains with operating the new system in foul weather conditions, and allowing maintenance teams to troubleshoot and rectify faults.

The new system was originally slated to run by the end of last year, but the LTA had said it needed to conduct more tests to ensure its reliability.