Michigan Driver's Education Practice Exam

In poor weather, stopping distance increases and visibility is reduced, so you need a larger space cushion than in clear conditions. The three-second rule is a baseline for good conditions; in foul weather you should give yourself more time by increasing the following distance beyond that. This extra space lets you react and stop safely if the car ahead slows or stops suddenly. To apply it, pick a fixed point ahead (like a sign), and when the vehicle in front passes it, start counting seconds; if you reach the point before you’ve counted four or five seconds, back off a bit more. This adjustment is needed in rain, snow, or ice and isn’t limited to highways—tailgating with only three seconds in poor weather can be dangerous.