All-day performance checks of the new signalling system on the North-South Line are necessary to 'work out teething issues', said rail operator SMRT in a blog post on Tuesday (6^th June). The new communications-based train control signalling system allows trains to run closer together, and arrive at intervals of up to 100 seconds during peak hours, instead of 120 seconds currently. Tests on the 30-year old North-South Line began in March, initially during the last hour of service on weekdays.

It then progressed to all-day tests on Sundays in April, and all-day weekday testing the following month (May). "As there are limited engineering hours each day (from 1:30am to 4:30am), it is not possible for us to accumulate adequate testing hours if we do not run the new signalling system during weekdays," said the rail operator. It added that trains fitted with the new system were put through 'rigorous checks' before being cleared for passenger service.

There were two delays on the North-South Line last week, following the beginning of the weekday signalling tests. A delay on Thursday (1^st June) was caused by a glitch in the computer server used to manage train schedules, while on Friday (2^nd June), delays were due to a fault in signalling equipment known as the Movement Authority Unit , said the Land Transport Authority and SMRT in a joint statement last Friday. "As we continue to intensify the testing of the new signalling system and until the system stabilises, there may potentially be more disruptions," warned SMRT on its blog, adding that it seeks the understanding of commuters during these tests.