Route
Junction number
1
Markerpost
30 km
Name
Denham Roundabout
Type
Non-standard interchange
Terminus
Terminus at end of exit list
Other routes
A40, A412, A4020
Authority
Restricted turns
Full access
Services
No services
M40 J1 Denham Roundabout
Layout and signage
| N/A | A412 A4020 |
|
A40 |
Central London A40 Slough (A412) Uxbridge (A4020) |
Lane configuration
- Lane 1 exits and returns after the junction.
- Lane 2 continues ahead.
- Lane 3 continues ahead.
- Lane 1 continues, with option to exit.
- Lane 2 continues ahead.
- Lane 3 continues ahead.
Other events
Start of motorway regulations
End of motorway regulations
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...
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.
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