SINGAPORE - As of November, a third of this year's train delays lasting more than five minutes were signal-related, said rail operator SMRT.

In a post on the SMRT blog last Friday, SMRT Trains managing director Lee Ling Wee wrote: "We expect these to reduce significantly after we successfully migrate our ageing signalling system to the new Communications-Based Train Control (CBTC) system."

The signalling systems on both the North-South (NSL) and East-West lines (EWLs) are being upgraded. The upgrade will allow trains to run at shorter intervals of 100 seconds, instead of 120 seconds now, thus increasing train frequency and reducing crowds in trains.

The current fixed-block signalling system divides the track into blocks of between 200m and 300m, and can detect where a train is only when it moves into a new section. For safety, trains are always kept at least one block apart from each other.

The new CBTC system relays the exact location and speed of every train to a computer, so they can travel closer together at distances of between 60m and 70m. Similar CBTC systems are already in use on the newer North-East and Circle lines.

SMRT said in its latest blog post that the new signalling system will be activated on the NSL in 2017, and that it is working hard to complete the project on the EWL by end-2018.

Faulty signalling hardware on a train was responsible for the mysterious interference which led to multiple delays on the Circle Line in late August and early last month, leading to slower train speeds and reduced service frequency.