Traffic gate to help alleviate M4 accident problems
A gate is to be installed on the central reservation of the M4 in Wiltshire which would stop motorists becoming stuck if the road is closed.
The Highways Agency said problems occur because of the 12-mile distance between junctions at Swindon and Newbury in Berkshire.
The gate would allow the agency to turn traffic around to the opposite carriageway after accidents.
A spokesman said the work would make the "vital artery" more resilient.
Highways Agency project manager Rob MacKenzie added the work would be complete by the end of January.
"The distance between junctions 14 and 15 is around 12 miles, which means that - if an incident closes the road - a lot of drivers can become stuck on the motorway," he said.