Weekday system-level performance checks on the new signalling system for North-South Line (NSL) commenced on 29 May 2017. As the new signalling system is fine-tuned by engineers, commuters may expect teething issues from the new system while aboard NSL trains between Marina South Pier and Jurong East. This guide explains some of the situations you may encounter on the NSL during the signalling checks.

1. Why is SMRT Trains changing to a new signalling system? What are the benefits to commuters?

The new signalling system will be more efficient than the current system, which has been in use since 1987. We will be able to safely reduce the distance between trains travelling on the network, and further increase the number of trains. This means shorter waiting times for commuters.

2. Why does the train stop between stations?

For safety reasons, all trains are programmed to maintain a distance between one another. Trains will not proceed if there is another train up ahead.

3. Why did the train overshoot the platform and have to reverse?

The new signalling system comes with various pre-set programmes to run and stop trains at various speeds. These pre-set programmes are being fine-tuned to suit different weather conditions. For example, the braking distance for a train arriving at Ang Mo Kio MRT Station (aboveground) on a clear day, would differ from that required during a thunderstorm. Wet tracks would require a longer distance for trains to come to a stop.

Trains may therefore not align correctly at station platforms. It is important to note that passengers will remain safe, as all trains are programmed to maintain a safety distance between one another. Trains will not proceed if there is another train up ahead. If the alignment is incorrect, trains will reverse for passengers to board and alight. In the rare event that the misalignment is more than 15 metres, trains proceed to the next station as programmed.

4. Why do the doors close so fast?

As we work towards the target of having more trains, and shorter waiting times for commuters, trains will have to stop for fixed intervals at stations. The new signalling system will also open and close doors automatically. The dwell time (i.e. the duration of trains stopping at station platforms) remains the same. Doors continue to remain open for about 30 seconds at most stations.

Please do not rush to board the trains. Please look out for light indicators and audio chimes, which indicate that train doors are closing. Train doors will close automatically soon after the lights flash and door chimes go off.

5. Why did my train brake suddenly?

Signalling systems are used to direct railway traffic. Trains move when the system indicates so, and stop when they receive a signal from the system. Signalling systems are built with safety as the top priority. Emergency brakes are applied when trains receive incorrect or conflicting signals, do not receive any signals momentarily, or when there are trains ahead. The signalling system is then reset, to ensure trains only move according to assigned signals.

6. Why are the performance checks carried out during peak hours? Can’t the checks be done during off-peak hours?

Trains fitted with the new signalling system have been put through rigorous checks before they were cleared for passenger service. Earlier trials took place during the last hour of passenger service, and progressed to whole of Sundays. Unlike new MRT lines where intensive testing can be conducted with a single type of train before passenger service commences, we are testing the new signalling system on an existing line with various train fleets. As there are limited engineering hours each day (from 1.30am to 4.30am), it is not possible for us to accumulate adequate testing hours if we do not run the new signalling system during weekdays. The June school holidays present the best opportunity for us to do so. We have to conduct all-day performance checks to work out teething issues that may arise when a new signalling system is introduced to a train network. The system-level performance checks on weekdays will allow us to further intensify tests of the new signalling system’s reliability. Our engineers will continue to monitor the system’s response to different situations, and trains services’ adherence to their schedules.

7. There were delays on 1 & 2 June 2017. What happened?

The first incident at 6.20pm on 1 June 2017 was due to a glitch in the computer server used to manage train schedules. This unfortunately caused all trains on NSL to halt. Although the back-up server kicked in quickly, operations controllers needed 30 minutes to manually reassign train schedules.

On 2 June 2017, a signalling equipment known as the Movement Authority Unit (MAU) registered a fault at around 4.48pm. The MAU fault resulted in slower train movement between Kranji and Admiralty stations. Signalling trials are part and parcel of new signalling systems and carried out to help train operators identify and resolve teething problems that may occur. As we continue to intensify the testing of the new signalling system and until the system stabilises, there may potentially be more disruptions. We seek the understanding of commuters.