How to Determine the Following Distance?
2 Answers
Methods to determine the following distance are as follows: 1. Use the rearview mirror to judge the distance of the vehicle behind: According to the physical principle that objects appear larger when closer and smaller when farther away, when the image of the following vehicle occupies one-third of the rearview mirror, the distance should be approximately 12 meters. When the image occupies half of the mirror, the distance is about 9 meters. If the image fills the entire mirror, the distance is roughly 3 meters. 2. Judging the distance to the vehicle ahead during urban driving: A general following distance of 3 meters is appropriate. When the rear bumper of the vehicle ahead is visible from the driver's seat, the distance is about 1 meter. When the lower edge of the bumper is visible, the distance is approximately 2 meters. Seeing the rear tires of the vehicle ahead indicates a distance of around 3 meters. 3. Utilize roadside reference objects: On highways, where following distances are greater, the above methods may not apply. In such cases, fixed objects like lamp posts can serve as references to estimate distance and maintain proper spacing. Typically, the distance between two adjacent lamp posts is equal and measures 50 meters, so three lamp posts represent the standard highway following distance of about 100 meters. Pay close attention when observing; if the time it takes for the vehicle ahead to pass from one lamp post to the next decreases, it indicates rapid movement, allowing for acceleration. Conversely, if the time increases, reduce speed appropriately.
Here's a practical tip for judging following distance while driving: observe the rear position of the vehicle ahead. When you can fully see where the rear tires of the preceding car contact the ground, the distance is approximately 5 meters; if only the lower edge of the bumper is visible, it's about 3 meters; when even the bumper's lower edge is obscured, the distance is less than 2 meters and you should immediately decelerate. Another method is the '3-second rule': pick a fixed reference point like a road sign, and when the front vehicle passes it, silently count '1001, 1002, 1003' - if you haven't reached the reference point by the time you finish counting, you're at a safe distance. On highways, extend this to 4 seconds, and add another second in rainy conditions. Personally, I maintain at least half a car length gap in heavy traffic to allow braking reaction time.
