What is the recommended following distance under good conditions on a freeway?

The standard rule is a 3-to-4-second following distance under good conditions. You measure it by picking a fixed point on the road (a sign, a tree), starting to count when the vehicle ahead passes it, and counting until you pass it: 'one one-thousand, two one-thousand, three one-thousand'. If you reach the point before you finish counting to three, you are following too closely. Increase to 4 or more seconds in rain, fog, snow, on slick surfaces, when towing a trailer, or when behind a large truck whose rear blocks your view. One- and two-second following distances are dangerously close: at highway speed, a one-second gap is only about 90 feet, far less than a typical braking distance.