Stopping takes much more road than most drivers expect. Before your brakes do anything, you need time to see the danger and move your foot. At higher speeds that time covers a lot of ground, and braking distance grows faster than speed.
Know the rule
There is no sure way to tell exactly how long it will take you to stop at a certain speed.
Handbook p. 42 ↗Your stopping distance depends on:
- Your own reaction time
- Weather and road conditions
- The weight of your vehicle
- The condition of your brakes
Three steps in stopping
| Step | Time | What happens |
|---|---|---|
| Perception | About .5 seconds | See/hear danger |
| Reaction | About .66 seconds | Brain tells foot to brake |
| Braking/stopping | Depends on speed | Press brake until car stops |
Estimated emergency stopping distance (feet)
| Speed | Reaction | Braking | Total |
|---|---|---|---|
| 20 mph | 44 | 15-22 | 59-66 |
| 30 mph | 66 | 33-50 | 99-116 |
| 40 mph | 88 | 53-107 | 141-195 |
| 50 mph | 110 | 83-167 | 193-277 |
| 60 mph | 132 | 120-240 | 252-372 |
| 70 mph | 154 | 163-327 | 317-481 |
| 80 mph | 176 | 213-427 | 389-603 |
Know the rule
In the table, reaction distance doubles when speed doubles (44 feet at 20 mph, 88 feet at 40 mph), but braking distance grows much faster (15-22 feet at 20 mph, 53-107 feet at 40 mph).
Handbook p. 42 ↗Know the rule
Safety tip: when the rear of the vehicle ahead passes a fixed point, count the seconds until you reach it. You are too close if you pass the point before counting four seconds.
Handbook p. 42 ↗Know the rule
Always increase your following distance on slick roads, when following large vehicles or motorcycles, at night, in fog or in bad weather.
Handbook p. 42 ↗Put it into practice
You're on the turnpike at night at 80 mph when a deer appears in your headlights. You travel about 176 feet before your foot even reaches the brake, and your total stop could take 389-603 feet. Slowing down and leaving space is your only real protection.