M4 smart motorway project in Berkshire completed

Work started on the M4 smart motorway scheme in 2018

Work to turn part of the M4 into a smart motorway has been completed.

A 32-mile section from Greater London through Berkshire is now fully open following the final closure at the weekend.

Smart motorways involve turning the hard shoulder into a running lane and using variable speed limits to control the flow of traffic.

Highways England said the completion of the £814m project would "cut congestion and further improve journeys".

• What are smart motorways and are they dangerous?

• How smart are smart motorways?

In January, the government paused the rollout of smart motorways amid safety concerns until five years' worth of data had been collected and assessed.

Schemes already under construction - including the M4 - have continued as it was deemed leaving cones and barriers in place during the pause would be disruptive.

Following the closure of the motorway between Slough and Maidenhead, the eastern section of the M4 between junctions 3 for Hayes and 8/9 for Maidenhead is now fully open with a 70mph limit.

A section between junctions 3 and 4 in west London will remain at 60mph to help manage air quality in the area.

If drivers get into difficulty, there are 34 emergency areas providing a place to stop, every 1.3 miles on average, National Highways said.

A new radar Stopped Vehicle Detection (SVD) system is also supposed to identify a stopped vehicle, typically within 20 seconds.

Mike Grant, National Highways delivery director, said drivers would benefit from "improved journey times".