The Land Transport Authority (LTA) and SMRT have detailed a series of measures to detect and prevent rail cracks on the MRT network, in response to a fourth crack found in five weeks on Friday.
The measures included replacing worn-out portions of the running rail earlier than scheduled, and appointing an international specialist to assess the condition of the rail.
A crack occurred on the eastbound track between Tiong Bahru and Outram Park stations on Friday night, which delayed journeys by up to 30 minutes.
At a media briefing to address that and previous occurrences, LTA deputy chief executive Chua Chong Kheng said the common factor was that all four incidents happened at curved tracks.
The rails are subjected to greater forces at bends, and thus are potentially more vulnerable, he said.
SMRT will thus focus on curved tracks along the North-South and East-West Lines. In all, 246 joints will undergo extensive ultrasonic tests and checks.
SMRT senior vice-president for engineering and maintenance Lee Ling Wee said checks will also be intensified on track components such as bolts and base plates.
The operator had called for a complete overhaul of the ageing MRT system on Friday. Yesterday, Mr Lee said SMRT will replace worn-out rails earlier as an added precaution. Currently, SMRT replaces rails that are worn down by 14mm. This threshold has been raised to 12mm, he said.
Under this new standard, about 40km of rail of the 400km long North-South and East-West lines have to be replaced, estimated to take about five years based on current procedures.
SMRT is in talks with LTA on expanding its facilities so it can produce longer stretches of rail to speed up replacements, he said.
Mr Chua said the LTA would study if more space can be made for pre-fabricating rails at existing or new depots.
The cost of replacing the rail under the new limits will be borne by SMRT, as this falls under the operator's obligation to maintain the railway in a safe operating condition, he said.
He added the LTA would conduct audits of SMRT's maintenance regime every two weeks, down from once a month.
An international trackwork specialist will also be engaged by next week to assess the rail system and advise if the rail maintenance regime needs to be changed, he said.
Both the LTA and SMRT stressed that safety was not compromised at any point. The signalling system is designed to detect rail cracks and prevent trains from entering the area where a crack occurs, Mr Chua said.
The earlier cracks took place on April 29, May 18 and Thursday. Prior to this year, there was an average of one rail crack a year.
Asked why the number of such incidents has gone up, Mr Chua said the cases appeared to be random. "It is too early at this stage to determine if there is any underlying or systemic issues that contributed to these four recent rail cracks."
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