Your overall stopping distance is made of two parts added together: how far the car travels while you react, and how far it travels while the brakes do their work.
Thinking distance is the distance the car covers in the moment between you seeing a hazard and actually pressing the brake. At a steady speed it's roughly the same number of feet as your speed in mph — and it grows if you're tired, distracted or have been drinking.
Braking distance is how far the car travels once the brakes are applied until it stops. This one climbs sharply as speed rises, because it's tied to the square of your speed — double your speed and braking distance roughly quadruples.
These are the typical overall stopping distances in good, dry conditions. They're worth memorising because questions often ask for the figure at a specific speed.
| Speed | Thinking | Braking | Overall |
|---|---|---|---|
| 20 mph | 6 m | 6 m | 12 m |
| 30 mph | 9 m | 14 m | 23 m |
| 40 mph | 12 m | 24 m | 36 m |
| 50 mph | 15 m | 38 m | 53 m |
| 60 mph | 18 m | 55 m | 73 m |
| 70 mph | 21 m | 75 m | 96 m |
Start at 20 mph = 12 metres. Then for each 10 mph step up, multiply the speed figure by a number that climbs by 0.5 each time: 20×0.6, 30×0.75(ish)… in practice the simplest trick is to learn the overall figures as a sequence — 12, 23, 36, 53, 73, 96 — and notice the gaps get bigger every time. That widening gap is the point the test wants you to understand.
Rather than measuring metres while driving, use time. As the vehicle ahead passes a fixed point — a sign or bridge — say "only a fool breaks the two-second rule." If you reach the point before you finish, you're too close. Double it to four seconds in the wet, and more on ice.
Following too closely is behind a huge share of real collisions. The theory test checks you understand not just the numbers, but that speed and conditions stack up — so expect questions that combine a speed with weather.
The best way to make these stick is to answer questions until the figures feel automatic. Try the safety margins topic, then prove it in a full mock test.
