Fourth lane on M4 smart motorway project to open this week

The M4 motorway upgrade will enter its final stage this week, with a new fourth lane and extra road safety features opening between Junction 3 (Hayes) and Junction 8/9 (Maidenhead).

National Highways is lifting the traffic cones and barriers on the upgrade, which started in 2018. A 60mph speed limit and other interim safety measures will remain in place while final technology tests are carried out.  

Due to the length of the upgrade, the removal of traffic management will take place over several nights. It started at 6am on Wednesday, July, 6.

When all the traffic management is removed, the four lanes will remain at 60mph while the new technology, including stopped vehicle detection, is undergoing tests.

Stopped vehicle detection uses radar technology to alert National Highways’ control centre, typically within 20 seconds. Operators can then close lanes with a Red X signal, display speed limits and deploy traffic officers.   

Temporary additional CCTV from the roadworks and a free recovery service will remain in place alongside the new permanent systems during the commissioning period.

Drivers will also be able to use any of the 16 new emergency areas if they need to stop in an emergency. Once the system is performing to an acceptable level at 60mph the maximum speed will be increased to the national speed limit. 

Mike Grant, National Highways Delivery Director, said:  

“Hundreds of thousands of people across the South East are already benefiting from the huge investment on the M4 which has taken place over the last few years when we opened the upgraded western section last year.  

“Virtually all construction work is complete, and as part of our final preparations we will now be undertaking work to calibrate the technology, including stopped vehicle detection. Safety continues to be our top priority, and we will not rush these essential preparations.  

“Once complete it means motorists along this whole 32-mile stretch of the M4 will benefit from improved journey times, and we ask drivers to bear with us while we prepare for opening.”