Rail operator SMRT Corporation is aiming for no more than one delay per month by 2020 - at least three times better than its performance today.

At its annual review yesterday, chief executive officer Desmond Kuek described this as "a bold target", which "only a handful" of the world's metros can match.

"Our goal is to reduce any delay to less than five minutes, and in the worst, ensure that it does not last longer than 30 minutes," he said.

"It is these major incidents, lasting longer than 30 minutes, that we must strenuously avoid."

Last year, SMRT had nine such incidents, excluding those related to a project to change out the signalling system - which determines how closely trains can travel to one another.

If signalling faults were included, there were 13 such long delays on the North-South, East-West and Circle lines - which are operated by SMRT. This was one more than what these lines chalked up in 2016.

If delays of more than five minutes were included, signalling-related delays totalled more than 140 last year, going by a chart provided by the newly privatised operator. Signalling-related delays formed the bulk of delays on its lines last year.

Mr Kuek said, however, that incidents related to the resignalling project were "temporal", and were thus excluded in its reliability count.

In response to questions on when signalling-related delays would be included in the count, SMRT chairman Seah Moon Ming said that they should be included from the end of June, when the new signalling system is completely operational on both the North-South and East-West lines.

Mr Seah said that the early closure and late opening of the two lines since late last year had provided SMRT with "nearly three times the engineering hours for maintenance, inspection and renewal works".

Asked how long this early closure and late opening would continue, the chairman said it would need to go on for at least the rest of this year.

"We cannot say forever," Mr Seah said. "But if there is a need, we will go for it."

As at the end of February this year, SMRT said the North-South Line had clocked 447,000km between delays, while the East-West Line posted 289,000km, and the Circle Line 564,000km.

Mr Kuek said: "With the com-pletion of key projects and stabilising of the new signalling system, we have seen positive results in rail reliability.

"While this is encouraging, there is more we can do to drive reliability even higher."

He noted that the company currently spends 60 per cent of fare revenue on maintenance, up from 50 per cent.

"Going forward, we are gunning for zero safety breaches and zero delays of more than 30 minutes," Mr Kuek added.

To do so, Mr Seah said the SMRT board has to "ensure that all SMRT assets are well maintained throughout their entire life cycles".