A solid topic for a driver safety meeting is avoiding rear-end collisions. They account for the largest portion of accidents on the road today. Often, this type of collision creates a chain reaction, leading to even more damage and possible injury.

A collision into the rear of a vehicle is almost always preventable, say traffic safety professionals. There are two types of rear-end crashes: “lead vehicle stationary” or “lead vehicle moving.” The incidence of the crashes when lead vehicle is stationary occurs at least twice as often as a moving lead vehicle crash, according to the Intelligent Vehicle Initiative (IVI).

IVI’s data further indicates that driving task errors account for the largest percentage of contributing factors for rear-end collisions. It categorizes driving task errors as:
Recognition errors (inattention, distraction and misperception).
Decision errors (driver chooses an improper action to avoid a crash).
Performance errors (driver brakes too lightly, freezes, over-steers, etc.).

Other research points to the main cause of rear-end collisions as drivers failing to detect slowed or stopped traffic, as well as not leaving sufficient distance between their vehicle and the vehicle in front to stop in time when there is a sudden and unexpected stop of the lead vehicle. This occurs most often at intersections, grade crossings, passenger stops and when slowing in preparation for turns.

Traffic safety professionals say there are several keys to preventing rear-end collisions. One is to continually scan the road ahead, keeping an eye out for potential traffic problems, adjusting one’s driving in changing conditions and being prepared to react. Another is to try to anticipate the actions of other drivers, but to never presume to know what another driver will do.

Maintaining an adequate following distance is one more key to preventing a rear-end collision. For normal driving circumstances, the National Safety Council (NSC) recommends a minimum three-second spacing between vehicles.

This is done by watching the vehicle ahead as it reaches some fixed object, for example, a sign, light pole or tree near the roadside. When the rear of this vehicle passes the object, you begin counting the seconds until the front of your vehicle reaches that object.

If your vehicle passes the object in less than three seconds, you are following too closely. You need to reduce your speed and increase the spacing to the vehicle ahead.

The amount of time and distance needed to safely brake to a stop increases the faster one drives and the larger the vehicle is. NSC advises adding extra seconds to following distance for highway speeds, heavy vehicle loads and adverse weather or hazardous driving conditions — such as reduced visibility or heavy traffic — and then altering following distance accordingly.

Remind your drivers that the way to avoid rear-end collisions is to manage the speed of their vehicles and the space around them according to the changing road, traffic and weather conditions, and be alert to safely react.

Various factors come into play to determine the distance it will take to bring a vehicle to a stop.

Speed (vehicle time and motion) — How far a vehicle will travel in a certain amount of time at a certain speed.

Perception distance — Time it takes to stop once a driver perceives an obstacle in the road and begins reacting to it.

Reaction time (also known as “thinking time”) — Time it takes to recognize a hazard and apply the brakes.

Brake Lag Distance — Distance a vehicle will travel in the time it takes for the buildup of brake force after the brake pedal is applied.

Braking Distance — Distance it takes a vehicle to stop after the brakes have been applied.

Total Stopping Distance — Combination of all of the above factors.