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We are making improvements to the A470 and M4 corridor.

Region / County:
south east
First published:
13 December 2019
Last updated:


Why we are doing it

Congestion on these roads is making journey times longer.

Other issues include:

  • high private car use
  • poor accident records
  • noise pollution
  • traffic pollution affecting air quality
  • sub-standard walking and cycling routes

The WelTAG stage 2 study recommends major interventions to solve the issues. This includes the planned Metro upgrade of the Valley Lines rail network. This upgrade should encourage the use of public transport.

Studies also identified the need for improvements on the A470 and M4. These proposals should manage the above issues.

Current progress

We have identified improvements for these roads.

On the A470 corridor proposals might consist of:

  • new signals
  • widening of slip road to ease queues
  • improved pedestrian and cycling links, including crossings at the A470 Nantgarw Interchange and Taffs Well Interchange
  • adding a third lane where possible to the A470 between Nantgarw and Coryton
  • better use of lanes on the A470 to help exiting vehicles
  • reducing the speed limit on the A470 from Pontypridd to Coryton to improve air quality and road safety
  • more signs with messages about current traffic problems

On the M4 corridor proposals might consist of:

  • improved widening at M4 junction 34
  • widening of entry lanes M4 junction 33
  • work will take place on the eastbound lanes to help exiting vehicle levels between M4 junction 33 and junction 34
  • an additional lane on three-lane westbound carriageway between M4 junction 33 and junction 34
  • more signs with messages about current traffic problems

There is potential for longer term metro and other public transport works.

Next steps

We will carry out WelTAG stage 3 studies to form the business case which will aid how we work out what schemes will improve vehicle flow.


Reports, environmental statements and plans