How did a safe MRT system indirectly cause delays?

Last Friday (Mar 19), Southbound trains towards Marina South Pier on the North-South Line (NSL) were delayed during the morning peak hours due to a fault with the platform screen doors at Bishan station. But how does ensuring safety for commuters indirectly cause inconvenience then?


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Safety Systems on MRT trains

A platform screen doors summary indicator at the ends of platform for train captains to know whether all 24 platform screen doors are proven closed and locked

A platform screen doors summary indicator at the ends of platform for train captains to know whether all 24 platform screen doors are proven closed and locked

Our MRT trains are equipped with many safety systems. One of which, is the interlocking system between the train doors and the station platform screen doors.

Simply put, if the train does not detect that both the train doors and the platform screen doors are proven closed and locked, it will not be able to depart.

Train Doors Platform Screen Doors Departure Clearance
Opened Opened Not Permitted
Opened Closed Not Permitted
Closed Opened Not Permitted
Closed Closed Permitted

Therefore, to override trains not being able to depart Bishan, the platform screen doors have to be isolated away from the signalling and interlocking systems.

But by isolating the platform screen doors away from safety systems, it will have to be manually operated and be checked visually by staff to ensure that there is no breach of safety.

Click to learn more about Platform Screen Doors »


Restricted Manual train operations

File Photo: A KHI C151 train approaching Bishan station

File Photo: A KHI C151 train approaching Bishan station

With the platform screen doors at Bishan being operated manually and isolated away from safety systems, trains are not allowed to travel in full Automatic mode at that section of track.


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Train captains will have to switch from Automatic to Restricted Manual just before entering Bishan. Under Restricted Manual, trains are limited to a maximum safe speed of 18km/h.

Train Mode Selected Maximum Safe Speed Train Operations
Automatic Mode (AM) Limited to 80km/h Fully Automated
Automatic Train Protection Manual (ATPM) Limited to 80km/h Manually Controlled
Restricted Manual (RM) Limited to 18km/h Manually Controlled

During the mode switchover from Automatic to Restricted Manual and vice-versa, passengers may have experienced some abrupt stopping before arriving and after departing Bishan.


Safe Distancing of trains

File Photo: A KHI C151 train at Ang Mo Kio station with a train queuing behind to arrive

File Photo: A KHI C151 train at Ang Mo Kio station with a train queuing behind to arrive

Trains have to be safely distanced as well. The signalling system will provide trains with a separation distance and a smooth brake curve for trains to decelerate, relative to either the train in front or a restricted section of track ahead (whichever closer).

But if the train behind comes within the safe distance to the train in front, safe distance ambassadors don’t come and saman la. The full service brakes or emergency brakes of the train behind will then be activated.

Especially during the morning peak hours, where more trains are put into the network. The chances of a more jerky ride will be higher. Even more when the train is operated manually and the train captain has to manually adhere to the maximum safe speed provided to them.

Click to learn more about Signalling Systems »


My opinion

At that point in time, I would have reacted the same as well – to feel annoyed and angry that I was affected by delays during peak hours.

But to take a step back and to think through, many people would have been activated to resolve the issue as soon as possible. The station staff who ensure commuters’ safety at the platform, the train service controllers who manage the peak hour traffic of MRT trains, the maintenance personnel who work tirelessly to rectify the issue, and the list goes on.

Although the platform screen doors did cause the fault, especially during the morning peak hours when people from all walks of life are going to school, work, etc., commuters’ safety must never be compromised.


Related Links
Platform Screen Doors – SGTrains
Signalling Systems – SGTrains

External Links
MRT delay on North-South Line during peak hour due to platform door fault – The Straits Times
Platform door fault at Bishan MRT Station slows rail services along North-South Line – TODAY
Peak hour delay on MRT North-South Line on Mar. 19 due to platform door fault – Mothership


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Loh

I'm a train enthusiast who is broadly interested in the different means of technology which powers Singapore's train network.