Skip to main content
Traffic Wales information line 0300 123 1213
The Welsh Government’s traffic information service for motorways and trunk roads in Wales

M4 J24 Coldra to J28 Tredegar Park– Installation of Average Speed Enforcement System 16/11/20-15/03/21


Where and Why?

Works will be undertaken to decommission the existing Variable Speed Limit (VSL) system between J24 Coldra and J28 Tredegar Park of the M4, and to introduce a new 50mph Average Speed Enforcement (ASE) system. 

These scheme is expected to: 


  • help manage on-going congestion issues along this stretch of the M4.
  • improve journey time reliability during peak times and provide smoother traffic flows.
  • reduce the risk of collision.
  • provide better air quality as toxic emission levels are reduced.

Diversions and Safety Measures

The majority of the scheme will be undertaken utilising lane 1&2 and lane 2&3 closures. Total closures will be required to complete the gantry works, finalise signs in the verge and central reserve, and to remove the VSL camera markings on all lanes unobstructed.

The diversion route for total closures between J24 Coldra and J28 Tredegar Park will utilise the A48 Southern Distributor Road (SDR). During full closures, signed diversions routes will be in place to manage the flow of traffic and advance notification signs will be provided.


Programme of Traffic Management Restrictions*

  • Due to associated safety requirements, these works will be undertaken overnight Monday to Friday, between 20:00 hours and 06:00 hours.
  • Total road closures will be in place on the M4 between junctions 24 Coldra to junction 28 Tredegar Park eastbound from March 1st-5th  and westbound from March 8th-12th. 
  • The 50mph speed limit between junctions 24 and 28 on the M4 will be live by Monday, March 15th.

**Please note, programme may be subject to change.


For further information, please contact Traffic Wales on 0300 123 1213 or via Twitter @TrafficWalesS

Call the Traffic Wales information line
0300 123 1213
Contact us