Train conductors are to be equipped with smart watches from Monday to help them ensure trains depart exactly on time.

Rail operator NS has spent two years developing an app which buzzes exactly 42 seconds before a train is due to leave the station, giving the conductor just enough time to get ready to blow the whistle.

The 1900 conductors who have requested the device say it will mean they can concentrate on helping passengers at other times without needing to check their watches.

A spokesman for NS did not disclose how much the project cost, but insisted the money was well spent. ‘Every second counts on the railway, so every second that we can run closer to schedule is a profit.’

A second batch of smart watches is due to be issued later this year to conductors who applied too late to be included in the first round.