DEFENSIVE DRIVING
Managing Visibility, Time and Space

Drivers must constantly process information to respond safely to conditions on the road. They are challenged to simultaneously manage visibility, time and space, as well as change.

Maintaining a safe following distance between your vehicle and traffic ahead allows you to see potential dangers ahead of the vehicle you're following, and remain visible in the mirrors of vehicles ahead of you.

In normal traffic under good weather conditions, a following distance of 2- to 3-seconds is safe. Traveling at 30 miles per hour, you cover 44 feet per second, equivalent to about five car lengths in 2 seconds.

This should give you enough time and space to respond to emergencies in heavy traffic, provided you are monitoring the action of the four or five vehicles ahead in your path of travel.

Apply the 2- to 3-second rule by doing the following:

  • Choose a fixed point along the road, such as a road sign, mile marker or tree.
  • Begin counting as the vehicle ahead passes the fixed point.
  • Count one-thousand-one...one-thousand-two...one-thousand-three until you pass the fixed point.

Allow 20- to 30-Second Visual Lead Time

You need enough time to span the road and the position of other vehicles so you can choose a safe path of travel and adjust your speed as conditions change. This lead time normally allows you to identify alternate paths around an accident or obstacle.

Monitor conditions and traffic at least 20 to 30 seconds ahead. At highway speeds of 50 to 65 miles per hour, the 20- to 30-second visual lead time translates to one-third to one-half of a mile. At city speeds of 30 miles per hour, 20 to 30 seconds equals one-and-a-half to two city blocks.

Apply the 20- to 30-second rule by using essentially the same method as the 2- to 3-second rule:

  • Choose a fixed point along the road, such as a road sign, mile marker or tree.
  • Begin counting as the vehicle ahead passes the fixed point.
  • Count one-thousand-one...one-thousand-two...one-thousand-three...one-thousand-twenty or one-thousand-thirty until you pass the fixed point.

Rank and Respond to Risks

A driver may be forced to respond to more than one risk at a time. The safest alternative is to adjust your speed and increase your scanning as soon as you become aware of a potential hazard. Position your vehicle so that you have the greatest space possible between your vehicle and any potential dangers.

For example, while driving on a narrow two-lane road, you might identify a pedestrian walking on the side of the road and a truck approaching in the oncoming lane. By adjusting your speed, you can avoid meeting the oncoming truck and passing the pedestrian at the same time. You have simplified the situation by separating one danger from another.

Although we expect other drivers to behave in an appropriate manner, we cannot depend on them always to drive as expected. That's why it's essential to practice managing visibility, time and space to protect everyone on the road.

Want More Information?

  • Your AAA club can provide additional traffic safety information and driver education materials.