Tackling disruptions during the morning peak hour should be a priority for the two train operators, said Transport Minister Lui Tuck Yew on Tuesday.
He said incidents during peak hours need to be reduced, as these cause the greatest inconvenience to the most commuters.
To do that, both SMRT and SBS Transit need to ramp up maintenance works at night and conduct more stringent checks on the condition of trains before launching them into service, said the minister.
But he also acknowledged that both firms have invested more money in maintenance, and are adopting a more predictive approach to detect and prevent problems from occurring.
Mr Lui was responding to five MPs who raised the issue of reliability, after a spate of delays that hit the rail network this year, several of which happened during the morning rush hour.
Government Parliamentary Committee for Transport chair Cedric Foo (Pioneer) said there were 10 incidents in the first three months of this year on various lines.
"Although nowhere as severe as the two major service disruptions in December 2011, the increased frequency of train disruptions has further diminished the commuter's confidence in the public transport system," he said.
Mr Lui said this year's incidents are a stark reminder that improving reliability is "a lengthy and painstaking journey".
Still, he noted that withdrawal rates have fallen by at least 25 per cent for the North-South, East- West, North East and Circle lines.
The overall trend of fewer trains being pulled out of service shows a move in the right direction, he said, adding that the goal is to bring the withdrawal rate below that of 2008 by 2016.
With tighter operating performance standards in effect since January, operators are also now accountable for short delays even if they do not lead to service disruptions, he said.
Mr Lui also took issue with a Straits Times report which alleged that the MRT system was less reliable than the New York City subway.
This was inaccurate, he said, as train reliability in the American city was measured in car-kilometres whereas Singapore uses train-kilometres.
As for capacity, new trains due this year and next year will allow the operators to improve frequency so commuters need not wait more than five minutes for a train, said Mr Lui.
Meanwhile, the Punggol West LRT loop will open in the middle of this year, with more rail lines to open in the coming years.
Mr Lui said: "As these new lines open, I think... crowdedness on certain existing stretches of the network should improve."
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