A55 J7 Cefn Du Interchange

Layout and signage

Gaerwen
Pentre Berw
A5152 (A5)
  A5152
(A5)
      Gaerwen
Llanfair Pwllgwyngyll
A5152 (A5)
Star

Lane configuration

LanesLanesLanesLanes

  • Lane 1 continues, with option to exit.
  • Lane 2 continues ahead.

LanesLanesLanesLanes

  • Lane 1 continues, with option to exit.
  • Lane 2 continues ahead.

In this section

What's new

The forever bottleneck, part 2

The second part of the story, where we learn why exactly the M4 gets narrower on the final approach to Europe’s biggest city.

The forever bottleneck, part 1

The M4 into London was one of the UK's earliest and most ambitious motorway projects. It was bold, pioneering... and almost instantly regretted.

Hello, here's my ridiculous side project

An introduction to what I write, and why I write it, and where my strange new road sign simulator fits in to all this.

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Have you seen...

Smart Motorways

Motorways used to be really simple. Now they have electronic signals, variable speed limits, emergency lay-bys, part-time hard shoulders... Just what is so smart about Smart Motorways?

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