Route
Junction number
21
Markerpost
122.8 km
Name
Chiswell Interchange
Type
Non-standard interchange
Terminus
Not a terminus
Other routes
M1
Authority
Restricted turns
Some turns restricted
Services
No services
M25 J21 Chiswell Interchange
Lane configuration
- Lane 1 is gained from the entry sliproad.
- Lane 2 continues ahead.
- Lane 3 continues ahead.
- Lane 4 continues ahead.
- Lane 1 exits and does not return.
- Lane 2 continues ahead.
- Lane 3 continues ahead.
- Lane 4 continues ahead.
Other events
Variable Speed Limits apply
- Variable Speed Limits apply
What's new
The road that made no sense
It was the UK's only single-carriageway motorway, and twenty years ago it ceased to exist. This is the story of the strange fascination it held, and of my place in history.
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.
Have you seen...
Aust to Beachley
Today two motorways cross the Severn near Chepstow. But as recently as 1965, the only crossing was a ferry that carried six cars at a time, from Aust to Beachley.
About this page
Published
Last updated
Published
Last updated
