Permit tests/Following distance
How far is a safe following distance?
Drag the speed and choose 2, 3 or 4 seconds. The gap you see is the distance your car covers in that time.
At 55 mph, a 3-second gap is about 242 feet, roughly 16 car lengths.
The gap in feet, by speed
| Speed | 2 seconds | 3 seconds | 4 seconds |
|---|---|---|---|
| 25 mph | 73 ft | 110 ft | 147 ft |
| 35 mph | 103 ft | 154 ft | 205 ft |
| 45 mph | 132 ft | 198 ft | 264 ft |
| 55 mph | 161 ft | 242 ft | 323 ft |
| 65 mph | 191 ft | 286 ft | 381 ft |
| 75 mph | 220 ft | 330 ft | 440 ft |
Distances are speed times time, rounded to the nearest foot. A car is about 15 feet long, so 3 seconds at 55 mph is roughly 16 car lengths.
How to count it
- Watch the car ahead pass a fixed mark, such as a sign, a bridge or a shadow.
- Count “one-thousand-one, one-thousand-two, one-thousand-three”.
- If you reach the mark before you finish, ease off the gas and count again.
Common questions
Pick a fixed point the car ahead passes, such as a sign or a bridge. Count "one-thousand-one, one-thousand-two, one-thousand-three". If you reach that point before you finish counting, you are too close. The gap in feet grows with your speed, which is why a time works better than a number of car lengths.
It is your speed in feet per second times three. At 55 mph you cover about 81 feet each second, so the gap is about 242 feet. The table on this page shows 2, 3 and 4 seconds from 25 to 75 mph.
Most driver manuals say to add time in rain, fog, snow or ice, at night, when towing, behind a motorcycle or a large truck you cannot see past, and when you are tired. Check your state's manual for its own figure, because a few say 4 seconds or more.
The idea is the same everywhere, and a time-based following distance is what permit tests ask. The number of seconds in the manual differs a little, so read your state's driver manual before the test.