Topic 10 of 14 · Speed limits
Speed limits, and why they are a ceiling
The national limits by road and vehicle, how to tell what limit applies when there are no signs, and why the appropriate speed is usually lower.
By the end of this lesson
- State the national speed limits for a car and for a car towing a trailer
- Work out the limit on an unsigned road from the street lighting
- Explain why a limit is a maximum in ideal conditions rather than a target
The numbers
For a car or motorcycle:
| Road | Limit |
|---|---|
| Built-up area | 30 mph |
| Single carriageway | 60 mph |
| Dual carriageway | 70 mph |
| Motorway | 70 mph |
For a car towing a caravan or trailer, everything drops:
| Road | Limit |
|---|---|
| Built-up area | 30 mph |
| Single carriageway | 50 mph |
| Dual carriageway | 60 mph |
| Motorway | 60 mph |
Towing also bars you from the right-hand lane of a motorway with three or more lanes.
The speed limit checker covers vans and buses too.
When there are no signs
A road with street lighting is normally a 30 mph limit, unless signs say otherwise.
That is the rule that lets you work out an unsigned road. If a different limit applies on a lit road, there will be repeater signs along it. Their absence is itself the signal.
On an unlit rural road you will usually meet the national speed limit sign — a white circle with a black diagonal. It does not tell you a number. It tells you to apply the national limit for your vehicle and the type of road you are on.
The part that matters more
The Highway Code is unusually direct about this:
The speed limit is the absolute maximum and does not mean it is safe to drive at that speed irrespective of conditions.
A narrow lane with blind bends and a 60 mph limit is not a 60 mph road. Neither is a 30 mph street lined with parked cars outside a school at half past three.
The question that actually decides your speed is:
Could I stop in the distance I can see to be clear?
If the answer is no, you are going too fast, whatever the sign says.
Where limits bite hardest
20 mph zones exist where people and vehicles mix closely. The difference between 20 and 30 is not a tenth of anything: it roughly halves the stopping distance, and it changes the likely outcome for a pedestrian from serious injury to a survivable one.
Temporary limits at roadworks protect people working metres from live traffic, and they are commonly enforced by average-speed cameras.
Variable limits on motorways, shown in a red circle on a gantry, are mandatory and enforceable.
Why it matters
Speed is the one factor that makes everything else worse at the same time. It lengthens your thinking distance, it lengthens your braking distance by the square, it narrows what you can take in, and it raises the energy in any impact.
Every other skill on this site — observation, anticipation, safety margins — buys you time. Excess speed spends it.
The three things to remember
- For a car: 30 in a built-up area, 60 on a single carriageway, 70 on a dual carriageway or motorway.
- Towing reduces it to 50 on a single carriageway and 60 on a dual carriageway or motorway.
- Street lighting normally means 30 mph unless repeater signs say otherwise.
⚠ The common mistake
Treating the number on the sign as the speed to drive at. A 60 mph limit on a narrow lane with high hedges is legal and completely inappropriate.
On the road
A 30 mph street with cars parked on both sides outside a school. The limit is 30. The speed at which you could stop for a child stepping out between two parked cars is a good deal less.
Check you have it
Answer these without scrolling back up. Retrieving something from memory is what makes it stick — rereading feels productive but does far less.
Preparing your questions…
Sources checked for this page
- The Highway Code — Rules 124 and 125, and the speed limits table
We summarise official guidance in our own words. Where the rules matter legally, check the official source. This site is not affiliated with DVSA.