Chapter 24: Following Distance
The Three-Second Rule
In good conditions, keep at least a three-second gap behind the vehicle ahead. To check it yourself: pick a fixed point on the road, like a sign or overpass shadow, and count the seconds between the car ahead passing it and you reaching the same point.
Adjusting the Gap
Extend that gap substantially in rain, fog, or heavy traffic, and increase it further at higher speeds, since stopping distance grows faster than speed does — doubling your speed roughly quadruples the distance needed to stop. Tailgating is one of the most common causes of rear-end collisions precisely because it eliminates the margin needed to react to sudden braking ahead.