THE Rail Accident Investigation Branch has started an inquiry into an incident on the West Coast Main Line, in which it is said a DB Schenker freight train rolled backwards for more than 1.5km towards Tebay from Shap Summit last Tuesday.

Four track workers were killed at Tebay when a trailer being used for permanent way maintenance ran away in 2004.

The RMT claimed only quick action by signallers at Carlisle had prevented another accident on Tuesday.

The union's general secretary Bob Crow said: "This is just the latest runaway rail vehicle, following incidents on London Underground and in Scotland, yet Network Rail is playing fast and loose with safety in the name of cutting costs.

"We have been calling for secondary protection for track workers during track possessions since Tebay."

Network Rail promised that safety would not be compromised. A spokesman said: "The Rail Accident Investigation Branch is looking into an incident in the early hours of Tuesday 17 August involving a freight train operated by DB Schenker.

"There were no people working on that section of railway and there were no passenger trains in the vicinity either."

He also said lookouts were still being used, and that workers were protected elsewhere in any case.

"Nonetheless, we are happy to talk to the RMT about any legitimate concerns it may have," he added.