The Land Transport Authority (LTA) is concerned about the fourth incident of a rail crack that has occurred on the North South East West Line (NSEWL) in recent weeks1, and is investigating the root causes of the incidents. In the interim, LTA will require SMRT to carry out more stringent checks and replace the running rails earlier where necessary.
2 LTA is investigating whether there is a systemic cause of the rail cracks. In the first two incidents, the cracks occurred at weld joints done by the same contractor. For the other two occurrences, cracks were detected on the rail itself, at two separate locations on the North-South and East-West Line. All four rail cracks occurred at locations where the tracks curve.
3 It is too early at this stage to determine if there is any underlying link or systemic issues that contributed to these four recent rail cracks. Nevertheless, SMRT has put in place various precautionary measures. First, SMRT has completed ultrasound checks on all 81 rail joints welded by the contractor involved with the rail joints in the first two incidences, and no defects have been identified. Second, SMRT will be stepping up checks on all curved track segments, including the rail joints and running rail itself. Third, SMRT is stepping up its running rail replacement programme and will replace rails earlier. The threshold for replacement has been reduced from a wear-limit of 14mm, to 12mm, as an interim precautionary measure, and LTA will review this threshold for replacement as part of its review of the MRT running rail maintenance regime.
Stepped up Audit Checks
4 Mr Chua Chong Kheng, Deputy Chief Executive, LTA: “LTA is monitoring SMRT's remedial actions very closely. While the design of the NSEWL ensures that trains are stopped when there is a rail crack, and passenger safety is not compromised at any time, we nevertheless take a very serious view of the recent occurrences. LTA will be stepping up audits on SMRT’s maintenance works. Audits will be stepped up to a fortnightly basis, instead of monthly, to ensure that checks are done thoroughly and rigorously. We will also focus our audits on the track curves, as the recent rail cracks have occurred along such stretches."
Appointment of international trackwork specialist
5 SMRT's system of running rail replacement is similar to the approach adopted by operators in other cities, whereby individual running rail segments are replaced when there are defects, or when the wear and tear for that rail segment warrants it. Nevertheless, to better determine what further measures can be taken to address the situation, LTA will be appointing an international trackwork specialist to assess the condition of rail and to advise on possible changes to the operator’s running rail maintenance regime.
6 LTA will carry out a detailed investigation into the four rail crack incidents to ensure that all contributory causes are properly addressed and will update the public at a later date.
1 The four incidences are: i) on 29 April along Somerset – Orchard northbound; ii) 18 May along Braddell – Bishan northbound; iii) 30 May along Yio Chu Kang – Ang Mo Kio southbound and iv) 31 May along Tiong Bahru – Outram Park eastbound.