Shropshire Council apologised for the disruption and added there were “multiple slips which are undermining the road edge along a 900m section”.

A number of lights were required and traffic control “over this distance is challenging”, resulting in lengthy delays, a spokesperson said.

“These can be exacerbated, and understandably so, by frustrated drivers who sometimes ‘run’ red lights, causing the lights to reset.”

Council engineers were sourcing signals that would work on a semi-permanent basis, off the electricity grid, until permanent repairs could take place, they added.

It was anticipated these signals would be installed about 10 March, subject to manufacture and connection to the grid.

The spokesperson said the council was investigating to ensure the valley remained open to traffic and so permanent repairs could take place over the summer.

It was anticipated road closures may be needed then, they added.