The report, along with recommendations and measures to counter these lapses, was submitted to Transport Minister Lui Tuck Yew on Tuesday.
SMRT said that they are reviewing and looking into the feasibility of the recommendations given by the COI before making the required implementations.
The COI was appointed to inquire into the disruption of MRT train services on December 15 and 17 last year, which affected more than 220,000 people and disrupted the train services for at least 10 hours in total over the two days.
It has since been found that there were several contributing factors and reasons that caused the disruptions.
Aside from the shortcomings in maintenance and monitoring of the ageing assets, there was also an inefficiency in the maintenance work culture at SMRT, stated the report.
However, it was stressed that the incidents was an issue of reliability of the train systems and not a safety issue.
Among the several recommendations listed, COI believed that SMRT could look into making improvements to their backup power supply in trains, examine the feasibility of equipping older trains to provide real-time information to detect train faults, and also to have better detection and monitoring of defaults in the train tracks and on the train itself.
Backup power supply
During the evening rush hour of December 15, four trains lost traction power and stalled on the north-bound track between City Hall and Braddell stations.
One of the trains' backup power system failed prematurely and passengers were left in the darkness and with limited ventilation before the train was hauled to a nearby station.
Another train had to detrain onto the track and passengers were made to walk through the tunnel.
COI recommended that SMRT could have improved on the trains' backup power supply as it was found that the capacity of the battery had deteriorated since the last check about two years earlier.
An increase in the frequency of such checks would have remedied the problem.
COI further notes that the batteries in the first generation trains are more than ten years old and the battery technology may have improved tremendously over the last few years.
If so, SMRT is recommended to consider replacing the existing batteries with news ones.
Multi-Function Vehicle
Another major fault was the lack of efficiency in SMRT's Multi-Function Vehicle (MFV).
The MFV conducts rail checks on various sections and it was sent out during engineering hours in the early morning of Dec 17, 2011.
However, because of a failure of the dated software of the MFV and reactive work processes, SMRT staff failed to detect and remedy the sag.
Four noth-bound and south-bound trains were stalled on their tracks and another train was pre-emptively detrained.
About 94,000 commuters were affected by the ensuing seven-hour disruption.
Besides an additional MFV that SMRT will be purchasing, COI recommends that SMRT replace the existing MFV and enhance the Standard Operative Procedure (SOP) for MFV operation to ensure that staff operate it in a manner that ensures accurate track measurements.
This incident could have been prevented if the existing MFV had been given a long-overdue software upgrade.
Hence a number of trains again encountered power supply problems on the morning of Dec 17.
Installation of steel caps
Expert witnesses have also concluded that the incident on Dec 15 was initiated by a defective fastener in the Third Rail Support Assembly (TRSA) which had a latent crack in its tongue.
Further investigation found that the TRSA claws had been dislodged and caused a sag in the third rail, which supplies electrical power to the trains.
This sagging caused damage to the trains' Current Collector Device (CCD) "shoes" and the trains were not able to draw electricity from the third rail, hence causing the disruption.
The third rail initially sagged by 40mm but the spring-mounted CCD shoes have a tolerance for sagging of up to 60mm. However, the sag caused the two adjacent
TRSAs to be more vulnerable to vibration and they gradually started to fail.
This caused the third rail to progressively sag further.
Although these material defects took time to develop, they were not identified and remedied under SMRT's maintenance regime.
It is believed that one or more trains had passed by the incident site just before the onset of the Dec 15 incident and they experienced some damage to their CCD shoes.
This then led to the Dec 17 incident.
The damaged CCD shoes from the trains rubbed against the third rail covers and further destabilized the third rail system elsewhere along the network.
This has led the COI to conclude that the design of the current third claw rail is also ineffective as it makes the claw susceptible to dislodgement.
They recommended installing steel caps to reduce the likelihood of dislodgements.
SMRT should also study if the design of the TRSA covers and claws can be improved to facilitate inspection.
Maintenance
COI also mentioned that SMRT should consider strengthening maintenance regime for the third rail system, train wheel defects and CCD's maintenance regime.
The COI concludes that the December incidents could have been prevented had adequate maintenance measures and checks been carried out.
COI's view is that SMRT exercised due prudence with regard to commuter safety, however, they paid inadequate attention to the well-being of passengers in stalled trains and stations.
The Committee has expressed confidence that the likelihood of similar occurrences in the future will be better managed if SMRT carries out the recommendations in the report.
Since the incidents, LTA and SMRT has been working together to implement measures to enhance the system's reliability. LTA said they will "carefully go through the findings and recommendations" and will provide a response when ready.
Mr Lui will make a Ministerial Statement at the July Parliament sitting to give the Government's response to the COI's report.
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