In the past five years, there have been on average 20 cases a year of irregular speed changes or sudden acceleration of MRT trains, said Second Minister for Transport Ng Chee Meng in Parliament yesterday.
The LRT lines had about two cases a year in the same period, he added in response to Non-Constituency MP Leon Perera, who had asked how often such incidents occurred.
Unexpected speed changes may occur because of temporary speed restrictions, put in place as a result of track maintenance or other renewal works being conducted.
Mr Perera asked how often train doors closed without warning. Mr Ng said there were 125 cases of this occurring in the MRT network each year over the same period, and fewer than one case a year for LRT trains.
The majority of such cases - irregular acceleration and doors closing suddenly - were on the North-South and East-West lines, which operate on an older signalling system, where drivers are responsible for opening and closing doors. "This introduces an element of human error," he said.
When the two lines complete their move to the new signalling system, doors will open and close automatically. "Barring any unforeseen developments, we are on track to complete the resignalling programme this June," said Mr Ng.
Earlier closures and later openings, as well as partial line closures, on the two lines on weekends since last December have helped speed up upgrading works, he said.
Responding to a request by Mr Henry Kwek (Nee Soon GRC) for an update on the shutdown of lines to facilitate work, Mr Ng said the shorter service hours have added the equivalent of 40 extra nights towards the installation and testing of the new signalling system.
He said the shortening of operating hours to facilitate other works, such as upgrading the power supply system, on the two oldest MRT lines was also being considered.