The three-second rule: stay at least three seconds behind the vehicle in front of you. When its rear bumper passes a fixed point, such as a sign or a shadow, count "one thousand one, one thousand two, one thousand three". If you reach the point before you finish, you are too close. Drop back.
Why seconds, not car lengths
Car lengths change with speed; seconds don't. At 30 mph three seconds is about 130 feet; at 65 mph it is about 285 feet. Counting seconds gives you the right distance at any speed without doing math.
Why three seconds
About a second and a half goes by before your foot even reaches the brake: you have to see the brake lights, understand them and move your foot. The rest is braking. Three seconds leaves room for both, if the car ahead brakes normally.
| Situation | Leave at least |
|---|---|
| Dry road, daytime | 3 seconds |
| Rain, fog or night | 4 seconds or more |
| Behind a motorcycle or a large truck | 4 seconds or more |
| Ice or snow | Much more: 8–10 seconds |
How to keep it
- Someone cuts in: ease off the gas and let the gap grow back. Don't brake hard.
- Someone tailgates you: leave even more room ahead, so you can slow gently.
- Heavy traffic: the gap still matters; a smaller gap just means more rear-end crashes.
What the rule is not
The three-second rule is about the space in front of you, which is the only space you control. It won't stop someone from rear-ending you, but it gives you room to slow down gently when the car ahead brakes, so the driver behind you has time too. It also helps with visibility: at three seconds back you can see past the car ahead to the traffic in front of it, and brake lights two or three cars up give you an early warning.
On a road test, following too closely is one of the faults examiners note most often. Count out loud on your first practice drives; after a week it becomes automatic.
See how far a car really needs
Most people guess stopping distances far too short. Try guessing where a car stops at 25, 45 and 65 mph.
Guess the stopping distanceStart ›The rule and its source are on rules of the road.
