SINGAPORE: Public transport operator SMRT will be fined S$3 million (US$2.33 million) fine due to lapses which led to an incident and subsequent six-day disruption along the East-West Line in September 2024.
In a report released on Tuesday (Jun 3), the Land Transport Authority (LTA) said these lapses included maintenance intervals being extended beyond stipulations, due to COVID-19 delays on new train arrivals.
A warning system that malfunctioned on the day of the incident also could have prevented the disruption, according to a report from the Transport Safety Investigation Bureau (TSIB) also released on Tuesday.
On Sep 25, a defective component known as an axle box dropped from a train and onto the tracks, causing a bogie - or an undercarriage with wheels - to come off the running rail between Dover and Clementi MRT stations.
This resulted in extensive damage to the tracks and other equipment, and disrupted MRT services along nine stations from Boon Lay to Queenstown.
An estimated 500,000 out of 2.8 million train journeys were affected on each day, with train services resuming six days later on Oct 1.
Buses offering free bridging services wait at Buona Vista station, as disruptions to the East–West line continued on Sep 26, 2024. (Photo: CNA/Vanessa Lim)
The train in the incident was among 66 in SMRT's first-generation KHI fleet which were rolled out in the late 1980s. They are progressively being replaced by new Movia trains.
Initially, 66 Movia trains were to be handed over to SMRT by March 2024, with the first batch in October 2021.
But due to the COVID-19 pandemic there was a delay of 1.5 years, and the first Movia train was only handed over in May 2023.
Upon receiving the first Movia trains, SMRT began decommissioning the KHI trains.
But SMRT was required to continue carrying out regular maintenance for the KHI trains still in service, including preventive works and overhaul - which refers to a complete tear-down and rebuild to restore it to an "as-good-as-new" condition.
But by the time of the incident on Sep 25, 18 KHI trains had been overhauled, but the incident train was not among them.
The stipulated overhaul interval was 500,000km, but SMRT twice extended the interval: First to 575,000km in August 2022, and then to 750,000km in August 2024.
At the time of the incident, the train had logged 690,000km since its last overhaul in 2018.
“These extensions were carried out based on SMRT’s internal procedures, and SMRT had relied on analysis of the performance of the KHI train fleet and their continued reliability in deciding on these extensions of the overhaul intervals for the incident train,” said LTA in its report.
The authority also noted that since axle box failures were not common, SMRT did not undertake a detailed engineering risk assessment on extending the axle box overhaul interval.
The root cause of the axle box failure could not be determined as key train components involved were too badly burnt and damaged in the incident, said LTA.
These parts were the axle box itself, which secures the wheels to the axle; the axle bearings, which reduce friction so the wheels spin smoothly; and the chevron springs which contain rubber to absorb shocks to keep the ride smooth.
They are part of the train’s bogie, which is the wheel assembly under a train car. The bogie had come off the third carriage of the train, causing extensive damage to the tracks.
A total of 46 rail breaks were identified in a 2.55km stretch between Dover station and stretching beyond Clementi station, which took days to repair.
Graphic: TSIB
Graphic: TSIB
While the root cause could not be determined, investigations concluded that the likely cause was degraded grease in the axle box, said LTA.
Grease is supposed to keep the components moving smoothly and prevent overheating. The grease can degrade when impurities enter, causing more friction than intended.
This can increase wear and tear on axle bearings, eventually causing overheating and failure.
The presence and location of burnt rubber and metal pieces from the chevron springs, found along the incident train’s path of movement, indicate the axle box had generated sufficient heat to burn the rubber of the springs.
The springs then progressively dropped off and eventually caused the axle box to dislodge, said LTA.
Graphic: TSIB
Missing axle box and chevron springs on bogie of the incident train. Photo: TSIB
Both LTA and TSIB noted the incident could have been prevented with a more timely overhaul of the train systems.
“Had the incident train been overhauled in a more timely manner, the condition of its axle box assemblies would have been checked and any degraded grease could have been replaced earlier,” said LTA.
TSIB noted that SMRT’s experience was that the axle boxes had been problem-free when its trains were overhauled at 500,000 km.
“However, when the overhaul interval was stretched beyond 500,000 km, the quality of the axle boxes and chevron springs, as well as their components, were no more assured,” said TSIB.
TISB noted in its report that on the morning of the incident, the defective axle box reached a temperature of 118 degrees Celsius, much higher than the typical operating range of 30 to 65 degrees Celsius.
This was detected by SMRT’s Hot Axle Box Detection or Hotbox system, which is set up along the tracks on both the East-West and North-South lines. The system has been in place since 2014, and consists of a trackside infrared sensor which measures the temperature of each axle box when a train passes by.
When the temperature of an axle box is detected to have exceeded a predefined value, the Hotbox system generates a warning. At the same time, an RFID sensor will detect which train is experiencing the issue.
Graphic: TSIB
SMRT's standard operating procedure requires a train controller at the maintenance engineering centre to monitor the Hotbox system and take follow-up actions in response to warnings.
On the incident day, a warning was displayed, but the train ID was not detected due to a system error. Instead, a “Null ID” was indicated.
The controller thus believed the warning was a false one, and did not take any follow-up action.
TSIB said SMRT’s prevailing procedures at the time of the incident, for resolving issues relating to the Hotbox system, were “not robust enough”.
The same issue of the train ID being undetected had occurred before, but the issue was not resolved, with staff treating these as false warnings.
“Operational staff could have been desensitised, resulting in diminished response to warnings and alerts over time,” TSIB concluded.
Had the warning been followed up on, the incident might have been prevented as the train would likely have been withdrawn to the depot earlier, the bureau added.
Engineers and technicians at Ulu Pandan depot working to conduct repairs and checks on the damaged tracks and equipment. (Photo: Facebook/Chee Hong Tat)
In determining the S$3 million fine, LTA said it took into consideration that SMRT had borne the cost of repairs as well as provided free bridging buses, regular bus services and shuttle train services at the affected stations.
SMRT also provided free travel to passengers alighting at Jurong East and Buona Vista stations for the six days of disruption.
The total cost of SMRT’s service recovery amounted to over S$10 million.
The financial penalty collected by LTA will go to the Public Transport Fund, which helps lower-income families with their public transport expenditures.
SMRT will have the opportunity to appeal the fine to the Minister for Transport.
In 2018, SMRT was fined a total of S$1.9 million over the Bishan Tunnel flooding incident in 2017 as well as a separate accident near Pasir Ris station in 2016, which left two SMRT trainees dead.
In 2015, SMRT was fined S$5.4 million for Singapore’s worst train disruption at the time, which affected 413,000 commuters.
SMRT was found to be fully responsible for the incident and to have fallen short in maintenance — failing to address water seepage in the tunnel between Tanjong Pagar and Raffles Place stations, for example.
In 2014, SMRT was fined S$1.6 million for four incidents that took place over 2013 and 2014, which included SMRT train drivers running red light signals.
SBS Transit was fined S$50,000 in 2014 for a 40-minute disruption caused by carelessness during maintenance works at Potong Pasir station.
In 2013, both SMRT and SBS Transit were fined a total of S$1.1 million for incidents over 2012 and 2013.
SMRT was fined S$860,000 for rail defects on the Circle Line, a safety breach at Ulu Pandan depot, its handling of a trackside fire at Newton Station (which incurred the highest fine of S$300,000) and for launching only three trains — instead of the scheduled four — from Bukit Panjang LRT Depot.
SBS Transit was fined S$250,000 for a service disruption on the NEL which led to stranded commuters having to wait in the haze for shuttle bus services.
In 2012, SMRT was fined S$2 million for two disruptions in Dec 2011 that affected 221,000 commuters.
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After the incident, SMRT preemptively withdrew from service all KHI trains that had exceeded 500,000 km mileage since their last overhaul, LTA noted. They then underwent overhaul activities for axle boxes before being put back into service, and this was completed in October 2024.
LTA has also developed an accelerated delivery programme for its new Movia trains, with the support of additional resources from SMRT and various contractors, to mitigate the delays from COVID-19. This will allow all KHI trains to be decommissioned by the third quarter of 2025.
SMRT has also worked with the Hotbox system manufacturer to rectify the Null ID indication issue.
It now requires its maintenance engineering centre to share system warnings with the operations control centre.
In consultation with LTA, SMRT has also implemented the use of data analytics for earlier detection of abnormal axle box temperatures, so that pre-emptive action can be taken.
TSIB also noted in its report that LTA was not involved in and did not review SMRT’s proposed extensions to the overhaul intervals of the trains.
LTA said that as asset owner, it has since strengthened its oversight of operators’ management of assets, including their internal procedures to adjust maintenance schedules.
“LTA and operators will work together for future overhaul decisions,” said LTA.
This means that LTA now requires rail operators to inform them of extensions to overhaul intervals.
LTA will further conduct an audit to assess the completeness of rail operators’ engineering assessment; and the appropriateness of any mitigating measures implemented such as operational adjustments, enhanced monitoring and increased maintenance, noted TSIB.
A Rail Safety and Reliability Review Workgroup has also been set up by SMRT, LTA and the National Transport Workers’ Union to review and enhance systems in areas such as life cycle management, asset renewal, system enhancements and maintenance practices across the rail ecosystem.
“As part of the review, the workgroup has engaged overseas metro operators in Guangzhou and Taipei for mutual learning,” said LTA.
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In a report released on Tuesday (Jun 3), the Land Transport Authority (LTA) said these lapses included maintenance intervals being extended beyond stipulations, due to COVID-19 delays on new train arrivals.
A warning system that malfunctioned on the day of the incident also could have prevented the disruption, according to a report from the Transport Safety Investigation Bureau (TSIB) also released on Tuesday.
On Sep 25, a defective component known as an axle box dropped from a train and onto the tracks, causing a bogie - or an undercarriage with wheels - to come off the running rail between Dover and Clementi MRT stations.
This resulted in extensive damage to the tracks and other equipment, and disrupted MRT services along nine stations from Boon Lay to Queenstown.
An estimated 500,000 out of 2.8 million train journeys were affected on each day, with train services resuming six days later on Oct 1.
Buses offering free bridging services wait at Buona Vista station, as disruptions to the East–West line continued on Sep 26, 2024. (Photo: CNA/Vanessa Lim)
BEFORE THE INCIDENT
The train in the incident was among 66 in SMRT's first-generation KHI fleet which were rolled out in the late 1980s. They are progressively being replaced by new Movia trains.
Initially, 66 Movia trains were to be handed over to SMRT by March 2024, with the first batch in October 2021.
But due to the COVID-19 pandemic there was a delay of 1.5 years, and the first Movia train was only handed over in May 2023.
Upon receiving the first Movia trains, SMRT began decommissioning the KHI trains.
But SMRT was required to continue carrying out regular maintenance for the KHI trains still in service, including preventive works and overhaul - which refers to a complete tear-down and rebuild to restore it to an "as-good-as-new" condition.
But by the time of the incident on Sep 25, 18 KHI trains had been overhauled, but the incident train was not among them.
The stipulated overhaul interval was 500,000km, but SMRT twice extended the interval: First to 575,000km in August 2022, and then to 750,000km in August 2024.
At the time of the incident, the train had logged 690,000km since its last overhaul in 2018.
“These extensions were carried out based on SMRT’s internal procedures, and SMRT had relied on analysis of the performance of the KHI train fleet and their continued reliability in deciding on these extensions of the overhaul intervals for the incident train,” said LTA in its report.
The authority also noted that since axle box failures were not common, SMRT did not undertake a detailed engineering risk assessment on extending the axle box overhaul interval.
Related:
ON THE DAY ITSELF
The root cause of the axle box failure could not be determined as key train components involved were too badly burnt and damaged in the incident, said LTA.
These parts were the axle box itself, which secures the wheels to the axle; the axle bearings, which reduce friction so the wheels spin smoothly; and the chevron springs which contain rubber to absorb shocks to keep the ride smooth.
They are part of the train’s bogie, which is the wheel assembly under a train car. The bogie had come off the third carriage of the train, causing extensive damage to the tracks.
A total of 46 rail breaks were identified in a 2.55km stretch between Dover station and stretching beyond Clementi station, which took days to repair.
Graphic: TSIB
Graphic: TSIB
While the root cause could not be determined, investigations concluded that the likely cause was degraded grease in the axle box, said LTA.
Grease is supposed to keep the components moving smoothly and prevent overheating. The grease can degrade when impurities enter, causing more friction than intended.
This can increase wear and tear on axle bearings, eventually causing overheating and failure.
The presence and location of burnt rubber and metal pieces from the chevron springs, found along the incident train’s path of movement, indicate the axle box had generated sufficient heat to burn the rubber of the springs.
The springs then progressively dropped off and eventually caused the axle box to dislodge, said LTA.
Graphic: TSIB
Missing axle box and chevron springs on bogie of the incident train. Photo: TSIB
Both LTA and TSIB noted the incident could have been prevented with a more timely overhaul of the train systems.
“Had the incident train been overhauled in a more timely manner, the condition of its axle box assemblies would have been checked and any degraded grease could have been replaced earlier,” said LTA.
TSIB noted that SMRT’s experience was that the axle boxes had been problem-free when its trains were overhauled at 500,000 km.
“However, when the overhaul interval was stretched beyond 500,000 km, the quality of the axle boxes and chevron springs, as well as their components, were no more assured,” said TSIB.
Related:
OVERHEATING COMPONENT NOT PICKED UP
TISB noted in its report that on the morning of the incident, the defective axle box reached a temperature of 118 degrees Celsius, much higher than the typical operating range of 30 to 65 degrees Celsius.
This was detected by SMRT’s Hot Axle Box Detection or Hotbox system, which is set up along the tracks on both the East-West and North-South lines. The system has been in place since 2014, and consists of a trackside infrared sensor which measures the temperature of each axle box when a train passes by.
When the temperature of an axle box is detected to have exceeded a predefined value, the Hotbox system generates a warning. At the same time, an RFID sensor will detect which train is experiencing the issue.
Graphic: TSIB
SMRT's standard operating procedure requires a train controller at the maintenance engineering centre to monitor the Hotbox system and take follow-up actions in response to warnings.
On the incident day, a warning was displayed, but the train ID was not detected due to a system error. Instead, a “Null ID” was indicated.
The controller thus believed the warning was a false one, and did not take any follow-up action.
TSIB said SMRT’s prevailing procedures at the time of the incident, for resolving issues relating to the Hotbox system, were “not robust enough”.
The same issue of the train ID being undetected had occurred before, but the issue was not resolved, with staff treating these as false warnings.
“Operational staff could have been desensitised, resulting in diminished response to warnings and alerts over time,” TSIB concluded.
Had the warning been followed up on, the incident might have been prevented as the train would likely have been withdrawn to the depot earlier, the bureau added.
Engineers and technicians at Ulu Pandan depot working to conduct repairs and checks on the damaged tracks and equipment. (Photo: Facebook/Chee Hong Tat)
WHY A S$3 MILLION FINE
In determining the S$3 million fine, LTA said it took into consideration that SMRT had borne the cost of repairs as well as provided free bridging buses, regular bus services and shuttle train services at the affected stations.
SMRT also provided free travel to passengers alighting at Jurong East and Buona Vista stations for the six days of disruption.
The total cost of SMRT’s service recovery amounted to over S$10 million.
The financial penalty collected by LTA will go to the Public Transport Fund, which helps lower-income families with their public transport expenditures.
SMRT will have the opportunity to appeal the fine to the Minister for Transport.
Past fines for train disruptions and incidents
In 2018, SMRT was fined a total of S$1.9 million over the Bishan Tunnel flooding incident in 2017 as well as a separate accident near Pasir Ris station in 2016, which left two SMRT trainees dead.
In 2015, SMRT was fined S$5.4 million for Singapore’s worst train disruption at the time, which affected 413,000 commuters.
SMRT was found to be fully responsible for the incident and to have fallen short in maintenance — failing to address water seepage in the tunnel between Tanjong Pagar and Raffles Place stations, for example.
In 2014, SMRT was fined S$1.6 million for four incidents that took place over 2013 and 2014, which included SMRT train drivers running red light signals.
SBS Transit was fined S$50,000 in 2014 for a 40-minute disruption caused by carelessness during maintenance works at Potong Pasir station.
In 2013, both SMRT and SBS Transit were fined a total of S$1.1 million for incidents over 2012 and 2013.
SMRT was fined S$860,000 for rail defects on the Circle Line, a safety breach at Ulu Pandan depot, its handling of a trackside fire at Newton Station (which incurred the highest fine of S$300,000) and for launching only three trains — instead of the scheduled four — from Bukit Panjang LRT Depot.
SBS Transit was fined S$250,000 for a service disruption on the NEL which led to stranded commuters having to wait in the haze for shuttle bus services.
In 2012, SMRT was fined S$2 million for two disruptions in Dec 2011 that affected 221,000 commuters.
Collapse Expand
LESSONS LEARNED
After the incident, SMRT preemptively withdrew from service all KHI trains that had exceeded 500,000 km mileage since their last overhaul, LTA noted. They then underwent overhaul activities for axle boxes before being put back into service, and this was completed in October 2024.
LTA has also developed an accelerated delivery programme for its new Movia trains, with the support of additional resources from SMRT and various contractors, to mitigate the delays from COVID-19. This will allow all KHI trains to be decommissioned by the third quarter of 2025.
SMRT has also worked with the Hotbox system manufacturer to rectify the Null ID indication issue.
It now requires its maintenance engineering centre to share system warnings with the operations control centre.
In consultation with LTA, SMRT has also implemented the use of data analytics for earlier detection of abnormal axle box temperatures, so that pre-emptive action can be taken.
TSIB also noted in its report that LTA was not involved in and did not review SMRT’s proposed extensions to the overhaul intervals of the trains.
LTA said that as asset owner, it has since strengthened its oversight of operators’ management of assets, including their internal procedures to adjust maintenance schedules.
“LTA and operators will work together for future overhaul decisions,” said LTA.
This means that LTA now requires rail operators to inform them of extensions to overhaul intervals.
LTA will further conduct an audit to assess the completeness of rail operators’ engineering assessment; and the appropriateness of any mitigating measures implemented such as operational adjustments, enhanced monitoring and increased maintenance, noted TSIB.
A Rail Safety and Reliability Review Workgroup has also been set up by SMRT, LTA and the National Transport Workers’ Union to review and enhance systems in areas such as life cycle management, asset renewal, system enhancements and maintenance practices across the rail ecosystem.
“As part of the review, the workgroup has engaged overseas metro operators in Guangzhou and Taipei for mutual learning,” said LTA.
Continue reading...