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Edwina Hart, Minister for Economy, Science and Transport

First published:
6 May 2014
Last updated:

This was published under the 2011 to 2016 administration of the Welsh Government



This statement provides an update on the traffic management system at the M4 Coryton roundabout.

Coryton roundabout is a strategic intersection of the M4 and A470, and a critical part of the motorway and trunk road network serving Cardiff and surrounding areas. We use advanced technology to control the flow of traffic at this junction. Each link of the roundabout is controlled by traffic signals. A central operating system automatically changes the timing of the signals in response to changes in traffic volume. The timing can also be changed manually in response to specific incidents. Driver compliance with the signals is monitored by detection cameras.

When traffic incidents occur at the junction we do all we can to assist and warn motorists of congestion. There are variable message signs on motorway and trunk road approaches to the junction. Traffic Officers can help remove vehicles following minor incidents or help the emergency services manage traffic during more serious incidents. Social media and radio bulletins provide information to road users.  

To ease some of the pressure on the junction, a dedicated slip road between the eastbound M4 and northbound A470 was successfully opened last year. A similar scheme to link the westbound M4 and northbound A470 will allow easier access onto the roundabout. These works are being undertaken outside of peak hours meaning little or no additional congestion during construction. This scheme will be opened in the summer.