MRT Service Disruptions on Newer Lines

Mr Png Eng Huat asked the Minister for Transport if he will explain why almost 50% of the 32 major service disruptions on MRT lines from 2010 to June 2013 happen on the newer lines and almost 30% of the breakdowns are attributed to the Circle Line.

The Circle Line was opened in stages from 2009. There were three service disruptions of more than 30 minutes each year from 2010 to 2012. In 2013, there have been none so far. Most of these disruptions were due to teething issues with its power system, it being a new line with new technologies. LTA and SMRT are now in the process of replacing the power cables. This should be completed this year. The cable replacement programme, as well as more frequent maintenance checks on the cables, will hopefully reduce the number of service disruptions on the Circle Line.

For the North East Line, we have seen more instances of disruptions beyond 30 minutes recently, mostly due to faults caused by stress corrosion cracking of components that secure its overhead power system, particularly in the tunnels between HarbourFront and Outram Park stations. This is due to unique and unexpected climatic conditions in these tunnels which are not observed in the tunnels of other lines, or even in the other parts of the North East Line further away from this particular stretch. These occurrences of stress

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corrosion cracking took place over time and did not show up in the initial years of operation. SBST has already replaced the affected components in this stretch of the tunnels and has stepped up the frequency of checks. LTA and SBST are also assessing the suitability of using more corrosive-resistant materials in the longer term. The service reliability of the North East Line should improve as these measures are put in place.