Stopping distance
Guess where the car stops, then watch it happen. Five speeds, dry and wet roads.
A child runs out at the red line. Where does your car finally stop? Drag the flag, then hit Brake.
Stopping distances by speed
| Speed | Reacting | Braking (dry) | Total, dry | Total, wet |
|---|---|---|---|---|
| 25 mph | 55 ft | 30 ft | 85 ft | 107 ft |
| 35 mph | 77 ft | 58 ft | 135 ft | 179 ft |
| 45 mph | 99 ft | 97 ft | 196 ft | 268 ft |
| 55 mph | 121 ft | 144 ft | 265 ft | 374 ft |
| 65 mph | 143 ft | 202 ft | 345 ft | 496 ft |
The table is a physics estimate, not a legal figure: 1.5 seconds to react, then braking at 0.7 g on dry pavement and 0.4 g on wet. The pattern is what matters. The reaction part grows in step with your speed, but the braking part grows with the square of it, so going from 30 to 60 mph roughly quadruples the distance your brakes need. On a wet road the braking part is almost twice as long again.
What it means behind the wheel
Most drivers badly underestimate these distances, especially at highway speed. That is the reason behind two rules on our rules of the road page: the three-second rule, which keeps enough space to react and brake behind the car ahead, and the basic speed law, which says to slow below the limit when rain, fog or traffic make stopping harder. Practice keeping three seconds on the Road Rules roads of Road Sign Adventure, and spot trouble early in Hazard Watch so you need less of this distance to begin with.
Questions people ask
What is stopping distance?
The distance you travel from the moment you see a reason to stop until the car stands still: reaction distance (before your foot reaches the brake) plus braking distance.
Why does doubling the speed more than double the distance?
Reaction distance doubles, but braking distance grows with the square of the speed: at twice the speed, the brakes need about four times as far.
Where do these numbers come from?
They are a physics estimate: 1.5 seconds to react, then braking at 0.7 g on dry pavement and 0.4 g on wet. Real stopping distances depend on the car, tires, road and driver, and are often longer.