Every road in Great Britain has a speed limit, even the ones with no number painted anywhere. When you see the 'national speed limit applies' sign — a plain white circle with a single black diagonal stripe — it isn't telling you to go fast. It's handing you back to a set of default maximums that depend on the type of road you're on and the type of vehicle you're driving.
For an ordinary car or motorcycle that isn't towing, there are really only four numbers to hold in your head: 30 in built-up areas, 60 on single carriageways, 70 on dual carriageways and 70 on motorways. Master those and most of the theory-test speed questions fall into place.
The catch is that the limit changes with the vehicle. Buses, coaches, larger goods vehicles and anything towing a trailer or caravan get lower defaults. So the honest answer to 'what's the speed limit here?' is always two questions: what road, and what am I driving?
Study time
30 min
Level
Core
Confidence
+10%
Practice
25 Qs
What you'll be able to do
- Understand how to know the speed limit even when you can't see a single sign.
- Understand the national speed limits for each road type — and why your van or trailer changes the numbers.
- Understand why the safe speed is often below the limit — and how good drivers choose their speed by the conditions, not the sign.
The facts that matter
- A white circle with a black diagonal stripe means the national speed limit now applies — it is not a 'go faster' instruction.
- Cars and motorcycles (not towing): 30 mph in built-up areas, 60 on single carriageways, 70 on dual carriageways, 70 on motorways.
- Street lighting usually signals a 30 mph limit unless repeater signs show a different number.
- Towing a trailer or caravan lowers your limits: typically 50 on single carriageways, 60 on dual carriageways and 60 on motorways.
- Every limit is a maximum for good conditions, never a target you must reach.
Make it stick
Memory anchors
Thirty in the streetlights
If a road has regular street lamps and no other signs, treat it as 30. The lamps are your clue that you're in a built-up area.
Sixty, seventy, seventy
Single carriageway 60, dual carriageway 70, motorway 70. One road type steps up, the last two share the top number.
Towing knocks ten off the top
Hitch up a trailer or caravan and your motorway ceiling drops from 70 to 60, with lower numbers on the smaller roads too.
Stay sharp
The mistakes everyone makes
Reading the stripe sign as 'speed up'
The white-circle-and-stripe sign only restores the default maximum. On a narrow single carriageway that default is 60, but the safe speed may be far lower.
Assuming a dual carriageway is a motorway
Both often carry 70, but towing changes things — a caravan on a dual carriageway is capped at 60, the same as on a motorway, not 70.
Ignoring the vehicle you're driving
Learners sometimes memorise the car figures and stop there. Buses, coaches and heavier goods vehicles have their own lower limits on the open road.
Out on the road
What this looks like in real life
The unlit country lane
No street lights, no signs, just the stripe sign at the edge of the village. That's the national limit: 60 on this single carriageway. The blind bends mean 60 would be reckless — the number is a ceiling, not an instruction.
The caravan on the M-way
You've hitched the caravan for a coast trip and joined the motorway. Cars around you sit at 70, but your limit is 60. Staying in the left two lanes and holding 60 keeps you legal and settled.
Go deeper
Lessons on this topic
Know the signs
Signs worth knowing here
Quick answers
Frequently asked questions
What does the white circle with a black diagonal stripe mean?
It means the national speed limit now applies. The actual number depends on the road type and your vehicle — it does not set a single fixed speed.
What's the speed limit on a road with street lights but no signs?
Usually 30 mph. Street lighting normally indicates a built-up area, unless repeater signs along the road show a different limit.
What's the national limit for a car on a single carriageway?
60 mph, provided you aren't towing. It rises to 70 on a dual carriageway or motorway. Always drive to the conditions rather than to the maximum.
Do the limits change if I'm towing a caravan or trailer?
Yes. Towing typically lowers you to 50 on single carriageways, 60 on dual carriageways and 60 on motorways, instead of the car figures.
Are national speed limits the same for buses and lorries?
No. Buses, coaches and larger goods vehicles have their own lower defaults on single and dual carriageways, so the car numbers don't apply to them.
Turn national speed limits into marks
Reading builds understanding — practice makes it stick. Pick up where this guide leaves off, free.
Revision checklist
0/5Tick each point once you can explain it without looking.