Quick answer
If a speed limit is displayed on a smart motorway, follow that limit. Variable speed limits can be used during busy periods, incidents, hazards, roadworks or poor conditions.
Do not assume the national speed limit applies when lower overhead signs are active. A speed limit shown in a red circle is mandatory.
What common smart motorway signs mean
50 / 60 in a red circle
Mandatory variable speed limit. You should not exceed the displayed speed.
Red X
Lane closed. You must not drive in that lane.
Amber warnings
Hazard, queue, incident or road condition warning ahead.
END or national limit sign
Restriction ends, but only increase speed when safe.
Why smart motorway limits change
- ✓Heavy traffic congestion
- ✓Breakdowns or collisions
- ✓Roadworks or lane closures
- ✓Poor weather or reduced visibility
- ✓To smooth traffic flow and reduce stop-start braking
Red X lane closure rules
A Red X means the lane is closed. There may be a broken-down vehicle, debris, road workers, emergency services or another hazard ahead.
- !Do not drive in a lane showing a Red X.
- !Move safely into an open lane when instructed.
- !Do not move back into the lane until signs show it has reopened.
- !Leave gaps to allow other drivers to merge safely.
Smart motorway cameras
Smart motorway cameras may enforce displayed variable speed limits and national speed limits where applicable. Treat cameras as active and follow the signed limit.
Average speed cameras and motorway cameras work differently. For a separate guide, read Average Speed Cameras: How They Work.
Important driver rules
- ✓Obey displayed speed limits.
- ✓Never drive in a Red X lane.
- ✓Keep a safe following distance in slower traffic.
- ✓Watch gantries ahead, not just the car in front.
- ✓Do not accelerate until restrictions end and it is safe.
Helpful UK speed limit guides
Frequently asked questions
Are smart motorway limits enforceable?
Yes. Mandatory variable speed limits shown in a red circle can be enforced.
Can smart motorway limits change quickly?
Yes. They may change because of traffic flow, incidents, lane closures, roadworks or weather.
What if one lane shows a Red X?
That lane is closed and must not be used until signs show it has reopened.
Does no sign mean 70 mph?
Usually the normal motorway limit may apply for cars, but always check nearby signs, roadworks and conditions.
Can smart motorway cameras catch speeding?
Yes. Cameras can be used to enforce speed limits on smart motorways.