Stopping distances come up in the theory test and are essential knowledge for real-world safe driving. The total stopping distance is made up of two parts: thinking distance (the time it takes you to react) and braking distance (how far the car travels while braking). Speed affects both — but braking distance increases dramatically the faster you go.
1The two components
Thinking distance is how far your car travels between the moment you see a hazard and the moment you actually press the brake. At average reaction time, that's roughly 1 metre per mph — so at 30 mph you travel about 9 metres before you've even touched the brake.
Braking distance is how far your car travels while actually stopping after you've applied the brakes. This increases much more steeply with speed — doubling your speed roughly quadruples your braking distance.
On wet roads, stopping distances at least double. On icy roads, they can be up to 10 times longer.
2The official stopping distances
These are from the Highway Code — learn them for your theory test:
• 20 mph: Thinking 6 m + Braking 6 m = Total 12 m (3 car lengths) • 30 mph: Thinking 9 m + Braking 14 m = Total 23 m (6 car lengths) • 40 mph: Thinking 12 m + Braking 24 m = Total 36 m (9 car lengths) • 50 mph: Thinking 15 m + Braking 38 m = Total 53 m (13 car lengths) • 60 mph: Thinking 18 m + Braking 55 m = Total 73 m (18 car lengths) • 70 mph: Thinking 21 m + Braking 75 m = Total 96 m (24 car lengths)
💡 Tips
- •At 70 mph, you need the length of a football pitch (96 metres) to stop safely.
- •The thinking distance increases roughly in proportion to speed, but braking distance increases as the square of speed.
3How to remember them for the theory test
A simple trick: the overall stopping distances in car lengths follow a sequence starting from 20 mph — 3, 6, 9, 13, 18, 24.
Or count the gaps: each speed adds about the previous figure in metres to the total. The key number to memorise is 96 metres at 70 mph — that's the one that surprises most people.
For the theory test, you may be asked about stopping distances at specific speeds or given scenarios about following distances. The rule of thumb for a safe following distance on dry roads: the two-second rule (stay at least two seconds behind the car in front).
💡 Tips
- •Two-second rule: pick a fixed point, when the car ahead passes it, count 'only a fool breaks the two-second rule' — you should still be saying it when you reach the same point.
- •In wet conditions, double the gap. In ice, multiply it by ten.
4What affects stopping distance?
Several factors can increase stopping distance beyond the Highway Code figures:
• Speed — the biggest single factor. • Weather — wet, icy or snowy roads reduce grip dramatically. • Tyre condition — bald or under-inflated tyres significantly increase braking distance. • Road surface — gravel, mud or poor quality tarmac reduce grip. • Vehicle condition — worn brake pads or discs increase braking distance. • Driver tiredness or distraction — increases thinking (reaction) time. • Alcohol or drugs — significantly increases reaction time.
A loaded car or van takes longer to stop than the same vehicle empty — the heavier the vehicle, the greater the braking distance.