Thirty percent of all crashes involve rear-end collisions, according to AAA, and that’s largely because many drivers fail to maintain a safe following distance from the vehicle ahead.

In ideal weather conditions in city traffic, drivers should allow at least three seconds between their vehicle and the vehicle ahead, AAA advises. At highway speeds, the gap should be lengthened to four seconds or more. In rainy conditions, the gap should be extended to six seconds or more.

Also, keep in mind that the heavier the vehicle, the longer it will take to come to a full stop.

Here are AAA’s steps to follow the three-second rule:

• Watch as the vehicle in front of you passes a fixed object or point.

• Begin counting as the vehicle passes the fixed object: “One thousand and one, one thousand and two, one thousand and three.”

• If your own vehicle reaches the marker before you finish counting, you’re following too closely.

• Remember to add an additional second to your following distance for each adverse condition, including driving at night, in fog, rain or snow; driving behind a truck or vehicle that’s obstructing your view of what’s ahead; driving behind a motorcycle; and driving through an intersection.