Motorists are being advised to leave extra time for their journeys, while work is undertaken to repair a damaged bridge near Carlisle.
St John’s Bridge, which carries Houghton Road North over the M6 between junction 43 and 44, is currently closed overnight so that the repairs can be carried out after it was hit by a high vehicle.
Work began on Monday and is expected to take two weeks to complete.
It means that the southbound carriageway of the M6 has been shut between the two junctions from 8pm until 6am.
Drivers must leave the southbound M6 at junction 44 and use the eastbound A689 towards Brampton and the westbound A69 to rejoin the motorway at junction 43.
During the day, the southbound carriageway will be reduced to two narrowed lanes with a 50mph speed limit in place.
The lane one closure is in place to allow the concrete used in the overnight repairs to harden during the day.
The local road, Houghton Road North, which uses the bridge to cross over the motorway, will be closed around the clock during the work.
Paul Hupton, project manager at Highways England, said: “The collision, several months ago, took a large chunk of concrete out of the bridge deck, exposing the steel reinforcement.
“There is no imminent risk to motorway users but the steel will corrode if the bridge deck is left unrepaired, resulting in concrete becoming loose and posing a safety risk to M6 traffic.
“We have looked closely at how best to do the work from a road user and contractor safety point of view and this is why we have opted for the overnight carriageway closures.
“While the diversion routes are able to absorb the relatively low volumes of traffic travelling overnight it would be worthwhile drivers allowing an extra 20 minutes for their journeys.”
The closure of Houghton Road North is causing minimal disruption, with many locals aware and finding alternative routes.
It was expected to cause the biggest disruption to motorists travelling from further afield who might be unaware.