The Land Transport Authority (LTA) and rail operator Singapore Mass Rapid Transport Corp. (SMRT) are accelerating and expanding an ambitious programme to rejuvenate the ageing North-South and East-West lines.

This will mean an expanded budget - last estimated by SMRT to be in the region of $900 million - though the operator and LTA have yet to find out the total bill, or decide how it should be split.

In addition to replacing the wooden sleepers which the metal tracks rest on and the signalling system, the network's power-supplying third-rail system will also be changed. The latter has been in the spotlight since two major breakdowns in December 2011 sparked a high-profile public inquiry.

SMRT Chief Executive Desmond Kuek said, "We've moved beyond pointing fingers. We just want to get the system back in shape. We realise that the system is as reliable and as robust as its weakest link."

According to the LTA, incidents on the North-South and East-West lines lasting more than 30 minutes each in the first quarter stood at 0.05 per 100,00km operated - 67 percent more than a four-year average between 2009 and last year.

But there were fewer incidents shorter than 30 minutes and disruptions caused by trains were also down. As of March, the number of trains withdrawn stood at 2.5 per 100,000km - down from 3.43 at the same time last year.

LTA Deputy Chief Executive Chua Chong Kheng said the aim is to bring this down to 2.11 by this year and 1.9 by the next.

Another fault highlighted at the public inquiry has also been all but resolved - that of poorly profiled wheels, which result in flat spots that are detrimental to the ride comfort and integrity of the rail system. Refurbishment of the oldest first generation trains - to change propulsion, electronic and pneumatic systems - is ongoing.

Mr Chua also revealed that three more three-car maintenance tracks will be built at the Bishan depot, in addition to the two six-car and five three-car-long tracks that are already there.

He added that a $195 million project to replace the signalling system - which will allow trains to run every 100 seconds instead of the current 120 - is now in the design stage. Resignalling will be completed in stages between 2016 and 2018.

At the same time, Mr Chua aims to finish a massive project to replace most of the network's 188,000 timber sleepers by 2016. SMRT has started on its own initiative to replace 28,300 of the oldest sleepers, which will cost $23.2 million. So far 11,000 have been replaced.

Going by that figure, the cost of the entire re-sleepering project could be between $150 million and $180 million. Again, it is not known how any such cost would be split.

Meanwhile, SMRT has been inspecting and monitoring the third rail and has carried out repairs and replacements where needed. The operator has also installed sensors on trains for live monitoring of the third rail.

Also under development is a laser scanner system that monitors the profile of 'collector shoes' - the parts of a train making contact with the third rail.

The Straits Times understood that the LTA will be reviewing the two lines' power cables - sections of which have suffered insulation faults in recent years.