How to Judge the Distance of the Rear Car from the Rearview Mirror?
3 Answers
Here are the methods to judge the distance of the rear car from the rearview mirror: 1. The larger the rear car appears in the rearview mirror, the closer it is to your car; the smaller it appears, the farther it is. 2. If the rear car occupies almost the entire rearview mirror, the distance is approximately 3m; if it occupies about 2/3 of the mirror, the distance is roughly 5m; if it takes up 1/2 of the mirror, the distance is about 9m; and if it occupies 1/3 of the mirror, the distance is around 12m. 3. If the rear car is located on the outer side of the rearview mirror, it indicates that it is very close to your car; if it is on the inner side, it means the distance is relatively far.
When I first started driving, I was figuring out how to judge the distance of cars behind me using the rearview mirror. Simply put, it's about observing the size changes of the following car in the central mirror. For example, if the car behind appears as a tiny dot in the mirror, it means it's far away; if it becomes quite large, occupying most of the mirror, then it's close, probably within ten meters. At this point, you need to be careful not to change lanes or brake too suddenly. In practice, I like to practice at red lights: watching a familiar license plate and observing its position in the mirror as it moves from far to near. Once it gets close and takes up a lot of space in the mirror, you know it's time to slow down. Don't forget, the side mirrors can also help, but the central mirror is the main tool. On highways, distance is even more critical—being too close can easily lead to a rear-end collision. So, developing this habit ensures safety, especially at night or in the rain when parallax is more pronounced. It takes practice to get used to it.
As a seasoned commuter, judging the distance of the car behind me relies entirely on accumulated experience. When looking in the rearview mirror, if the car behind is far away, it appears as small as a sesame seed; at a medium distance, the car body occupies about a quarter of the mirror; when it's close, the front or license plate nearly fills the mirror frame, indicating roughly a two-second following distance. I once had a near-miss on the highway because I failed to notice these changes in the mirror, so now I remind myself to glance frequently. During everyday driving, especially when turning, using the mirror to judge distance can prevent collisions—for example, if the car behind appears larger in the mirror, I delay turning. Another trick is to factor in speed: at higher speeds, the car behind shrinks more slowly in the mirror; the opposite is true at lower speeds, so stay alert. Safety first—don’t get distracted by chatting or music and ignore changes in the mirror.
