A421 Harrowden Interchange

Layout and signage

Hitchin
Shefford
Bedford
A600
  A600     A600  

Lane configuration

LanesLanesLanesLanes

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

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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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Ringways

The story of an incredible plan to reshape London into a city of motorways, with the history from creation to cancellation and details on every unbuilt road.

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