Passengers who have suffered an ever-lengthening catalogue of problems on the months-old new Caledonian Sleeper fleet have been hit with yet another – emergency exit windows being locked shut.
Operator Serco told Scotland on Sunday it had been caused by a “circuit fault”.
Rail safety regulators said the move was to prevent windows opening and being hit by another train.
News of the latest problem with the troubled £150 million fleet comes days after new figures showed passenger complaints had trebled since it was introduced.
Previous glitches include toilets and showers not working because of pipework damaged by chemicals, software locking doors and poor room cleaning.
There have also been staff shortages and strikes, emergency brakes being triggered and a train failing to stop in Edinburgh.
The window exits are designed for use when passengers cannot escape through their room doors and out along the corridor, such as if a carriage crashed on its side.
Staff are said to be unhappy.
A rail source said: “There is a coach in service at the moment which has all the emergency windows locked shut so you can’t use them. Though not the primary escape route, they are still an escape route in an emergency.
“It’s a bit alarming to know that should there be an emergency, escape would’ve been delayed because of locked exits, and, depending on the emergency, could pose a real risk.”
The Rail, Maritime and Transport union (RMT), which represents most Sleeper staff, said it had been informed.
A spokesperson said: “RMT is fully aware of the problem and its serious nature. We are consulting with our reps on the Sleeper over both a solution and any further action required to ensure safe operation.”
The Office of Rail and Road, which regulates safety, said: “Normally in an emergency situation, the safest place is inside the train, as the vehicle is designed to protect the passengers.
“Should evacuation be necessary, the primary route is via the doors.
“In an extreme situation, such as the vehicle being on its side, windows can be used.
“Normally, windows are secured but not locked, and have sensors to notify the train manager if they are open.
“On rare occasions, a false signal may be sent and the train manager is required to assesses the situation and may need to lock the window.
“Windows are secured to prevent an open window fouling the path of trains on adjacent lines.”
Ryan Flaherty, Serco’s managing director for Caledonian Sleeper said: “Clear processes and standards exists to assess and manage any risks so the safety of our guests and staff is not compromised.
“The emergency windows have been designed, approved and risk assessed and if there is a fault with a window they can be locked until the problem is resolved.
“As you would expect, guest and staff safety is always our number one priority and the new Caledonian Sleeper fleet is fully compliant with all mandated safety standards. We would never run a service unless it is compliant.”