How to Use Rearview Mirrors to Judge the Distance of the Following Vehicle?
4 Answers
The method to judge the distance of the following vehicle from the rearview mirror is as follows: 1. Size: The larger the size of the following vehicle in the rearview mirror, the closer it is to the leading vehicle; the smaller the size, the farther it is. 2. Analysis: If the following vehicle occupies almost the entire rearview mirror, the distance is approximately 3m; if it occupies about 2/3 of the mirror, the distance is approximately 5m; if it occupies about 1/2 of the mirror, the distance is approximately 9m; if it occupies about 1/3 of the mirror, the distance is approximately 12m. 3. Position: If the following vehicle is located on the outer side of the rearview mirror, it indicates that the following vehicle is very close to the leading vehicle. If it is located on the inner side, it means the following vehicle is farther away.
After driving for so many years, judging the distance of the car behind me through the rearview mirror mainly relies on instinct and observation habits. For example, on the highway, if the car behind only occupies about one-third of the mirror, it means it's still dozens of meters away; if it takes up half the mirror, it's dangerous, possibly just ten meters or so. Practicing on open roads while driving and glancing at the mirror to observe how the size of the car changes at different distances will naturally build memory. Additionally, at night or during rain, poor lighting makes judgment harder, so it's safer to stay focused and slow down. Remembering this trick can reduce rear-end accidents by half. I always remind my friends to habitually glance at the mirror before hitting the road to ensure safety.
When I was learning to drive, the instructor always emphasized checking the rearview mirror, and it has indeed made driving much easier for me. The simplest method is to focus on the relative size of the car behind: if the car's front is so small that details are indistinguishable and it looks like a tiny dot, the distance is at least 50 meters or more; if it occupies more than half of the mirror and appears huge, it's time to lightly tap the brakes to increase the gap. Be extra cautious on rainy days, as reflections can be distracting—it's best to gently test the brakes to gauge the following car's reaction. I use this technique regularly while driving, which helps avoid sudden braking and fosters safe habits. I recommend beginners practice parking in different spots in a parking lot first, observing how the size of the following car changes in the mirror to develop a feel for it.
Judging the distance of the following car using the rearview mirror relies on visual proportion, with maintaining distance being the safety baseline. If the following car appears very small in the mirror, occupying less than a quarter, it's far away; when it approaches half the mirror, you should be alert and slow down. Combining changes in speed makes the judgment more accurate—for example, if the following car rapidly enlarges on the highway, it indicates it's approaching, and you should adjust accordingly. Developing small habits in daily driving, like glancing at the mirror when starting at a green light to anticipate, can prevent many minor scrapes.
