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His Royal Highness The Duke of Edinburgh, 10 June 1921 to 9 April 2021

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We want to improve the junction 48 interchange.

First published:
2 March 2021
Last updated:

For traffic news visit Traffic Wales.


Project status: planned
Region/county: south west Wales

Why we are doing it

Junction 48 is the main junction for accessing Llanelli and Pontarddulais. 

Upgrading this junction will improve safety and reduce congestion. We will upgrade the existing path for cyclist and pedestrians.

Presentation explaining the project

What we are doing

There are several issues with the layout of the A4138 and M4 J48 that contribute to congestion. They include:

  • limited opportunity for right turning traffic at A4138 to M4 eastbound on-slip. This impedes traffic heading towards Hendy
  • A4138 from Hendy layout with give way junction to traffic joining the M4 eastbound slip road
  • A4138/M4 westbound slip road layout peak times. The right turn lane junction relies on ‘goodwill’ of the A4138 traffic to exit the slip road at peak times
  • A4138 southbound from the M4 J48 towards Llanelli lane discipline is poor. The offside lane is not used as much as it could be used
  • no provision for cyclists.

We want to:

  • reduce congestion
  • reduce queuing during peak times
  • improve air quality
  • reduce driver frustration
  • improving safety.
  • improve connectivity
  • improve journey times
  • improve active travel through shared use path for cyclist and walkers
  • improve pedestrian and cyclists crossings.

The proposed works will involve:

  • carriageway widening to increase efficiency of the A4138.
  • new traffic signals on the M4 westbound off-slip and Tal-y-Coed junctions
  • lane management measures on the A4138 southbound
  • improvements of all M4 junctions with the A4138
  • shared use facility to tie in new route between the A4138 and Llangennech
  • environmental improvements for habitats such as dormice

Find out more

If you have any concerns or queries you can contact: