SMRT will continue to do "everything possible" to improve the reliability of its rail network, said chief executive Desmond Kuek, giving his strongest comments yet on minimising train delays.
They come just weeks after three disruptions last month, which prompted Transport Minister Lui Tuck Yew to express his disappointment with SMRT.
In an interview with The Straits Times, Mr Kuek said SMRT has invested "significant resources" to improve reliability on the ageing North-South and East-West lines. It is refurbishing all major systems on older trains.
For instance, it has replaced the power supply units on its first-generation trains and upgraded software on third-generation trains to reduce propulsion faults, which accounted for nearly a third of trains withdrawn from service in 2011 and 2012.
Signalling issues, another significant cause of withdrawals in the past three years, are also being addressed.
SMRT Trains executive vice-president Lee Ling Wee said the operator is replacing all ageing signalling equipment on the trains first, even though these have to be changed again by 2018 when a new signalling system is in place.
Apart from investing in better hardware, including new sensors to detect faults such as sags in the power-supplying third rail, SMRT will also beef up its technical workforce by about 100 to 200 engineers in the next few years, to complement the more than 100 already onboard. More technicians will also be brought in.
Improvement works on the ageing lines may affect commuters, however - SMRT is planning to close the two lines earlier on some evenings from April so its engineers have more time to work.
Closures on weekends are also a possibility.
The changes, said Mr Kuek, are in line with SMRT's "zero-defect" attitude to its operations.
"Every delay or disruption is investigated, and we do this to address the root cause of every incident so that we can bring out the relevant lessons to be learnt to avert future occurrence," said the former chief of defence force.
The renewal programme - co-funded by the Government - is unlikely to cost $900 million, as estimated earlier.
The measures implemented have caused the number of delays to come down overall. There were 302 incidents that caused delays of above five minutes on these two lines in 2011, and 277 in 2012. This dropped to 229 last year.
The number of trains withdrawn due to technical faults also decreased by 32 per cent.
SMRT shared how it compares with other metros in terms of delays. In 2012, it ranked 10 out of 29 metro operators in the CoMET Nova Group, which includes operators such as the Hong Kong MTR and the London Underground.