Adequate Following Intervals
The need for adjustments in following time occurs when speed or road conditions change. The distance for steering is much shorter than it is for stopping (note: the heavier a vehicle is, the longer it takes to stop). Response time with the hands is close to ½ second while response time with the foot is normally ¾ second. This does not take into account any lag in perception time due to fatigue, drugs, or inattention, etc. All time and distance relationships are designed for the best driving conditions.
- A 2-second interval provides the driver time to steer out of problem areas at all listed speeds on a dry surface and braking out of problems at speeds less than 35 mph.
- A 3-second interval provides the driver time to steer out of problem areas at all listed speeds on dry surfaces and braking out of problems at speeds to 45 mph.
- A 4-second interval provides the driver time to steer out of problems at all listed speeds on dry surfaces and braking out of problems at speeds up to 70 mph.
When driving, it is important to maintain a safe following distance between you and the vehicle in front oft you. The amount of distance you should keep depends on the speed you are traveling. At lower speeds, the recommended following distance is at least three seconds. At higher speeds, the recommended following distance increases to four or more seconds. This allows you enough time to react in case the vehicle in front of you has to brake or swerve suddenly . To determine if you are maintaining a safe following distance, wait until the vehicle in front of you passes a fixed object like a sign or tree, and then count the seconds until you pass the same object. If you reach the object within three seconds, you are too close and should increase your following distance.