Safe Driving Practices and Following Distance
The space cushion
The most tested safe-driving idea is following distance. Use the three-second rule: pick a fixed object ahead, and when the rear of the vehicle ahead passes it, count "one-thousand-one, one-thousand-two, one-thousand-three." If you reach the object before three, you are too close. Add at least one second for rain, darkness, or heavy traffic, and more for ice or fog. At highway speed, three seconds is roughly the length of a football field.
Scanning and control
Look about 12 seconds ahead, check mirrors every 5-8 seconds, and glance over your shoulder before changing lanes because mirrors leave blind spots. Keep a cushion to the side as well as ahead: avoid riding beside another vehicle. In a skid, ease off the gas and steer where you want to go; do not slam the brakes. If you begin to hydroplane, slow gradually and avoid sudden steering. Use low beams in fog, rain, and snow - high beams reflect back and reduce visibility.
Traps
A favorite question offers a fixed distance in feet; the correct answer is usually the time-based rule, because the gap must grow with speed. Another trap: the three-second gap is a minimum in good conditions, not a target for bad weather. And following-distance questions often hide a large vehicle ahead - if you cannot see the truck's mirrors, the driver cannot see you, so drop back.
Worked example
You are following a car at 55 mph and count only two seconds. You are too close: at that speed you need at least three seconds, and four in rain.