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 sunlit uplands
On Saturday 31 May something historic happened. The Heads of the Valleys Road was finally complete.
Grand openings
Our much-loved Opening Booklets section has two new publications for you to explore, and we’re making some overdue changes to make them easier to find and easier to read.
Silver bullet
The Silvertown Tunnel is finally open for business. One question remains: what’s it for?
Have you seen...
Junction Three
The M621 has one junction where everything leaves the motorway and heads for the city, and a very bizarre junction it is too.
About this page
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