Stopping distances
Your stopping distance is how far you travel while you react (thinking distance) plus how far the car takes to stop (braking distance). Pick a speed and a road.
Speed
Road
23 metres
9 m thinking + 14 m braking. About 6 car lengths.
Typical stopping distances on a dry road
| Speed | Thinking | Braking | Total |
|---|---|---|---|
| 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 |
From The Highway Code's typical stopping distances. In the wet, stopping distances are at least double (rule 227); on ice they can be ten times as long (rule 230).
The two-second gap
On fast roads, leave at least two seconds between you and the vehicle in front: count two seconds from when it passes a fixed point, such as a lamp post, to when you reach it. Double the gap on wet roads, and allow up to ten times on ice (rule 126).