Keep a three-second gap

Summary

This pattern is for drivers and motorcycle riders. It describes measuring your following distance in seconds rather than metres, so the gap grows automatically with speed and leaves time to react and stop.

Recommendation	Why?
Keep at least three seconds behind the vehicle in front.	It takes time to notice a hazard, move your foot and brake, and three seconds gives a reasonable margin in good conditions.
Count from a fixed point: when the vehicle ahead passes a sign or shadow, count “one thousand and one, one thousand and two, one thousand and three”.	If you reach the point before you finish counting, you’re too close.
Double the gap in rain, at night, in fog or when towing.	Stopping distances grow on wet roads, visibility is lower in the dark, and a heavier vehicle takes longer to stop.
Leave more room behind trucks, buses and motorcycles.	Large vehicles block your view of what’s ahead, and motorcycles can stop more quickly than you expect.
When stopped in traffic, stay far enough back to see the rear tyres of the vehicle ahead touching the road.	You have room to steer around it if it stalls, and you’re less likely to be pushed into it if you’re hit from behind.
Don’t close the gap because someone is tailgating you.	Ease off gently to widen the gap in front, which gives you both more time to stop, or let them pass when it’s safe.
When someone cuts into your gap, drop back and rebuild it.	The gap only works if you keep it, and it’s quicker to lose a car length than to have a crash.

Context

This pattern suits everyday driving in towns and on open roads, in any country and whichever side of the road you drive on.

It does not suit stop-and-go queues at walking pace, where the stopped-traffic rule applies instead, or ice and snow, where you need far more than six seconds and should consider not driving at all.

There’s a trade-off between space and flow. In heavy traffic a three-second gap invites other drivers to cut in, and it can feel like you’re losing ground. This pattern chooses the safety margin, because the time lost is small. Road authorities differ on the minimum: some recommend two seconds in good conditions and others three or more, so check your local road rules and treat three seconds as a sensible floor.

Usage

Setting the gap: pick a fixed point ahead, count as the vehicle in front passes it, and adjust your speed until you can finish the count. Recheck every so often, especially after speed changes.

In lane changes and merges: a good gap makes merging easier for everyone, see Merge like a zip.

Near your destination: looking for a park while following closely is a common cause of nose-to-tail crashes. It helps to decide where you’ll stop in advance, see Park before you arrive.

References

Your national or state road authority and driver’s handbook give the official following-distance guidance and road rules where you drive.