Stopping distance is the total distance a car covers from the moment a hazard appears to the moment it stops. The Highway Code splits it into two parts, thinking distance and braking distance, and the figures are worth knowing, both for the theory test and for judging a safe gap on the road.
The two parts
Thinking distance is how far the car travels while the driver reacts, sees the hazard, decides to brake, and moves their foot to the pedal. It is based on a reaction time of just under 0.7 seconds, and it rises by 3 metres for every 10mph.
Braking distance is how far the car travels once the brakes are applied, until it comes to rest. This is the part that depends on grip, and so on the tyres and the road surface.
The Highway Code figures (dry road)
On a dry road with a typical car, the Highway Code gives:
- 20mph: 6m thinking + 6m braking = 12m
- 30mph: 9m + 14m = 23m
- 40mph: 12m + 24m = 36m
- 50mph: 15m + 38m = 53m
- 60mph: 18m + 55m = 73m
- 70mph: 21m + 75m = 96m
The striking part is how the braking distance grows. Thinking distance rises steadily, but braking distance climbs far faster, because it is roughly proportional to speed squared. Doubling the speed roughly quadruples the braking distance, which is why 70mph needs so much more room than the numbers might first suggest.
Why weight barely matters
A common surprise: a heavier car does not take meaningfully longer to stop. The extra weight presses the tyres down harder, generating proportionally more friction, and the two effects largely cancel. Braking distance is set by the grip between tyre and road, not by the mass of the car, which is exactly why the tyres matter so much.
Wet and icy roads
The dry figures are a baseline. On a wet road, braking distance roughly doubles, with the added danger of aquaplaning in standing water. On ice or snow, overall stopping distance can stretch to as much as ten times the dry figure. Thinking distance does not change with the weather; it is the braking half that grows, and good tyres are what limit how far. Keeping a healthy set, replaced in good time with tyres bought online from Tyres.co.uk, helps keep those distances as short as they can be.
This is the reasoning behind the two-second rule, and why it becomes at least four seconds in the wet: the gap has to cover the longer distance the car now needs.
From the workshop: the number that lands with people is 70mph, 96 metres dry, getting on for double that wet. That is the thick end of two football pitches to stop from a motorway speed. It makes the case for leaving a proper gap better than any lecture.
Sources and accuracy. These figures reflect the Highway Code at the time of writing and are averages, not guarantees; real distances vary with car, tyres, road and driver. Anything safety-critical should be confirmed against the current Highway Code. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What is the stopping distance at 70mph?+
The Highway Code gives 96 metres at 70mph on a dry road, 21 metres of thinking distance plus 75 metres of braking distance. That is around 24 car lengths. In the wet it is far more, as the braking part roughly doubles.
What is the difference between thinking and braking distance?+
Thinking distance is how far the car travels while the driver reacts, before the brakes are touched. Braking distance is how far it travels after the brakes are applied, until it stops. Added together they make the total stopping distance. Tyres affect the braking part, not the thinking part.
Why does stopping distance double in the wet?+
Because there is less grip. On a wet road the tyres cannot generate the same friction, so the braking distance roughly doubles. On ice it is far worse, overall stopping distance can be up to ten times the dry figure. Thinking distance stays the same; it is braking that suffers.
Does a heavier car take longer to stop?+
Not really, in terms of braking distance. A heavier car presses its tyres down harder, generating more friction, which roughly cancels out the extra momentum. This is why the Highway Code figures don't change with vehicle weight, though brakes and tyres still have to cope with the load.