M4 set to be expanded to four lanes in peak times
Government plans have been put forward to expand the M4 motorway to four lanes in a bid to ease congestion during peak periods.
The Highways Agency, which manages the core road networks in England, wants to create a 'managed motorway' between junctions three and 12 to help relieve congestion on the busy commuter link.
The changes, which would affect 31 miles of motorway between the A312 at Heathrow Airport and Theale, propose introducing a system of varied speed limits and allowing the use of the hard shoulder as a running lane during busy times.
Treasury secretary Danny Alexander announced the Government's commitment to the project in his spending review last month.
The Highways Agency hopes to deliver the scheme in the early years after the next spending review period after 2015.
The project is estimated to cost between £525m-£720m and would see cameras, information signs and signals installed as the variable speed limits are enforced.
The agency hopes the changes will improve journey times and road safety, while minimising the environmental impact, particularly on trips to Heathrow and between London and Reading.