MRT Trains collide at Joo Koon

This article will be progressively updated as more information is released. Last updated 16 Nov 2017.

Just over a month after the flooding incident, another major accident plagued the MRT system during the morning peak hours of 15 November 2017. At around 8:20am, a moving train collided into the rear of a stationary train at the westbound platform of Joo Koon MRT Station, leaving at least 36 people injured.

Two C151A trains, trainsets 535/536 and 547/548 were involved. These trains are the fourth generation of rolling stock on the North South Line (NSL) and East West Line (EWL), entering service between 2011 and 2014.

The incident was attributed to a software glitch in the Communications-based train control (CBTC) signalling system which was in the undergoing implementation at the time of the incident.

How the incident unfolded:

Prior to social media postings by the public, SMRT had reported the incident as a “Train Fault”. Netizens took their experiences to social media, posting photos and their experience of the collision on Facebook. The Singapore Civil Defence Force (SCDF) later confirmed that there were injured passengers in a tweet at 10:45am.

At the onset of the incident, SMRT announced a 20-minute delay as bi-directional train services were routed through the unaffected eastbound platform at Joo Koon.  Later in the day, train services were suspended between Joo Koon and Tuas Link to facilitate the recovery of the trains. A full timeline is attached at the bottom of this article.

A strong initial suspect in this rail collision incident was the operability of the signalling system during the incident. Trains operate on the new Communications-based train control (CBTC) signalling system from Pioneer to Tuas Link. Implemented earlier last year, faults with the new signalling system have plagued both the North South Line (NSL) and Tuas West Extension (EWL) with a history of regular signalling faults, although most issues have been ironed out prior to the incident.

Trains switch from the old Westinghouse fixed-block system to the Thales CBTC system at Pioneer Station in both directions of the EWL. As Joo Koon is firmly within CBTC operating zones, emergency brakes should have activated on the moving train when it violated its limit of movement authority. 

At 11:18am, SMRT released its first official statement via its Facebook page:

This incident was the second collision incident to affect the Singapore MRT network. The first MRT collision occurred during the morning peak hours of 5 August 1993 at Clementi station towards Jurong, resulting in 156 injured passengers. It was caused by a 50-litre oil spill from a maintenance locomotive.


Preliminary Sequence of Events

In a press conference on the night of 15 November 2017, LTA, SMRT Trains & Thales elaborated on their preliminary reconstruction of events. Details of the incident were extracted from the press conference, including the LTA-SMRT joint statement as well as the Question & Answer segment of the press conference.

Another press conference was held on Tuesday, 21 November 2017 with more details regarding the incident.

 

Two days before the incident, Thales connected the passive CBTC system with the active CBTC system. Prior to this, both passive and active CBTC systems on the East West Line were isolated.

On the morning of 15 November 2017, at 5:38am, trainset 535/536 (a Kawasaki-Sifang C151A train) departed Ulu Pandan Depot in the eastbound direction and began revenue service on the East West Line, turning around at Pasir Ris. At the reception track of Ulu Pandan Depot, before joining the eastbound mainline, the train encountered “an abnormal condition within the CBTC train borne signalling equipment”. This condition is likely to be the interrupted connection between the 2 Vehicle On-Board Controllers (VOBC) located at both ends of the train, resulting in the train to be reflected as a “3-car configuration” on the new (Thales SelTrac CBTC) signalling system instead of the actual 6-car operation configuration of NSL and EWL Trains. This is referred to as the first CBTC protective bubble.

As a protection layer against faults like the above-mentioned, Thales has developed and implemented the Non-Communicating Obstruction (NCO) “software protection module”. When the NCO is activated, trains are only able to move in Restricted Manual (RM) mode, at a maximum speed of 18 km/h. This is referred to as the second CBTC protective bubble.

The NCO was disabled when the train passed by Point W210B near Clementi MRT Station whose circuit was yet to be modified for the new CBTC signalling system. By design, the train should only able to operate in RM at 18km/h under the CBTC system. However, as the CBTC signalling system is only operated under a shadow mode between Pioneer and Pasir Ris, the train continued to operate normally under the Legacy signalling system.

Train Captains are only required to monitor instruments related to the Legacy signalling system between Pioneer and Pasir Ris as it is the signalling system used by trains for that stretch. The CBTC signalling instruments are not visible to Train Captains at that stretch.

While transiting between the old (Legacy Westinghouse fixed block system) and new signalling system at Pioneer MRT Station towards Tuas Link, the train can only travel, by design, only at 18km/h in RM due to the earlier signalling abnormality which is only visible to the Train Captain from Pioneer to Tuas Link. The Train Captain reported the abnormally to the Operations Control Centre (OCC) immediately at Pioneer. By procedure, the train was planned to return to Ulu Pandan Depot after de-training passengers at Joo Koon.

The Train Captains and Train Controllers were taught that there would always be at least a protective bubble under the active CBTC system.

At 0818hrs, this faulty train pulled into Joo Koon MRT Station (Platform B) to detrain passengers due to “an anomaly in the train signalling system”. The station’s Half-Height Platform Screen Doors had to be manually operated via a switch located at the HeadWall of the Platform (front end of the platform). Once the platform screen doors were opened, Track Circuit Protection (TCP) was applied, which indicates to the new signalling system that the entire Platform B of Joo Koon MRT Station was occupied.

Joo Koon MRT Station - Platform B
Joo Koon MRT Station – Platform B, prior to the opening of the Tuas West Extension

At 0819hrs, the rear train, another C151A Train (trainset 547/548), stopped 36m away from the rear of the faulty front train which was at Joo Koon MRT Station Platform B. This was due to the TCP that was in place for the faulty train at the platform. (Log findings indicated 36m instead as revealed during the second press conference instead of 10.6m estimation from video footage during the first conference)

At 0820hrs, after the detrainment of the faulty train at Joo Koon Platform B, the Train Captain closed the Platform Screen Doors, which resulted in the TCP being lifted to allow the faulty train to move off. As the faulty train was only reflected as a 3-car configuration in the signalling system, the rear train (547/548) started to move forward automatically under the control of the new signalling system which wrongly assumed that it was clear to proceed. It collided with the stationary train at about 16 km/h, pushing it forward by the length of roughly two doors.

At least 36 people on the rear train (trainset 547/548) were injured, including the Train Captain, an Assistant Station Manager and 6 Malaysian commuters. There were a total of 517 passengers onboard the rear train at the time of the incident, while the front train had no passengers onboard. The 36 injured people also included commuters who independently sought medical attention at hospitals after the incident.

The Train Captain of Trainset 547/548 had 1.5 years of driving experience on the North South and East West Lines at the time of the incident.


Aftermath

East West Line

As a result of the train collision at 0820hrs, SMRT advised commuters via various channels such as in-train/in-station announcements as well as on Social Media.

  • 0825hrs: To add 20 minutes additional train travel time from Jurong East to Joo Koon due to “a train fault at Joo Koon”
  • 0835hrs: Free regular bus services between Jurong East and Tuas Link stations activated
  • 0837hrs: To add 30 minutes additional train travel time from Jurong East to Tuas Link due to “a train fault at Joo Koon”, and that train service is still available
  • 0926hrs: To add 30 minutes additional train travel time from Queenstown to Tuas Link due to “a train fault at Joo Koon”
  • 0958hrs: To add 15 minutes additional train travel time from Jurong East to Tuas Link
  • 1031hrs: To add 10 minutes additional train travel time from Boon Lay to Tuas Link
  • 1358hrs: No Train Service between Boon Lay and Tuas Link. Free bridging bus services and free regular bus services available between Boon Lay and Tuas Link
  • 1715hrs: Train Service between Boon Lay and Tuas Link resumed, with an additional 10 minutes travelling time from Boon Lay to Tuas Link
  • 1734hrs: Free bridging bus services and free regular bus services between Boon Lay and Tuas Link ended
Reduced North South Line Trains

As a precaution to prevent a similar incident on the North South Line, as it is operated using the new CBTC signalling system, the number of trains deployed during the evening peak hours on 15 November 2017 were reduced to allow for a larger gap between trains.

SMRT advised commuters via various channels such as in-train/in-station announcements as well as on Social Media regarding this as well.

  • 1705hrs: Additional 15 minutes train travel time on the entire North South Line due to fewer trains serving. Free one-way bus bridging service from Bishan to Yishun were available, as well as two-way free regular bus boarding at Bishan, Ang Mo Kio, Yio Chu Kang, Khatib & Yishun.
  • 1745hrs: Additional 25 minutes train travel time on the entire North South Line
  • 1829hrs: Additional 40 minutes train travel time on the entire North South Line
  • 2019hrs: The free one-way bus bridging service from Bishan to Yishun as well as the two-way free regular bus boarding at Bishan, Ang Mo Kio, Yio Chu Kang, Khatib & Yishun has ceased
  • 2218hrs: Normal train service on the North South Line

The Days Ahead

Following the incident on 15 November 2017, more arrangements were made by the Land Transport Authority as well as SMRT Trains to facilitate the investigation to the incident. Changes to train services are detailed at Suspension & Changes to Train Service on Tuas West Extension.

To facilitate the speed up the works for the new signalling system on the East West Line as well as additional engineering works, several East West Line and North South Line stations will close earlier, open later as well as remain closed on selected days.


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