Union leaders have demanded double-crewing of all Northern Line trains and daily safety checks after the emergency braking system failed for the fourth time in as many weeks.
The RMT union said it would give complete support to drivers exercising their right to refuse to move Northern Line trains on safety grounds.
The emergency ‘trip-cock’ braking system, designed as a ‘failsafe’ that triggers automatically if a train passes a signal at danger, has failed on four occasions since 9 September, most recently on Wednesday.
“This system is designed to prevent the potentially disastrous consequences of trains passing signals at danger, and the seriousness of these failures cannot be understated,” said RMT general secretary Bob Crow.
“After last night’s failure, we are no longer asking but insisting that all Northern Line trains are double-crewed and that each train is checked daily before coming into service until the problem is identified and eliminated.
“The disruption to services that these enmergency measures will cause is preferable to running the risk of a potential disaster – it is as simple as that,” he added.