Route
Junction number
4B
Markerpost
27.5 km
Name
Thorney Interchange
Type
Terminus
Not a terminus
Other routes
M25
Authority
Restricted turns
Full access
Services
No services
M4 J4B Thorney Interchange
Layout and signage
Lane configuration
- Lane 1 exits and returns after the junction.
- Lane 2 exits and returns after the junction.
- Lane 3 continues ahead.
- Lane 4 continues ahead.
- Lane 5 continues ahead.
- Lane 1 exits and does not return.
- Lane 2 exits and returns after the junction.
- Lane 3 continues ahead.
- Lane 4 continues ahead.
- Lane 5 continues ahead.
Other events
Variable Speed Limits apply
- Variable Speed Limits apply
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.
Have you seen...
M1 under construction
Pictures taken as the first section of the M1 was being built in 1958-9, with all its unique architecture still under construction.
About this page
Published
Last updated
Published
Last updated
