What is the method for judging the distance between cars through the rearview mirror?

[McSkylar]

The method for judging the distance between cars through the rearview mirror is: 1. Use the center of the rearview mirror as a reference line. When the car body is on the outside of the reference line and the rear vehicle cannot be fully seen, the distance is 5 meters; 2. When the rear vehicle can fully appear in the rearview mirror and the car body is pressed against the reference line, the distance is 10 meters; 3. When the rear vehicle is pressed against the central axis of the rearview mirror and there is still a width of one car between the vehicle in the rearview mirror and the outer edge of the rearview mirror, the distance is 15 meters; 4. When the rear vehicle is pressed against the central axis of the rearview mirror and there is a width of two cars between the rear vehicle and the outer edge of the rearview mirror, the distance is 20 meters.

[OAlivia]

After years of long-haul truck driving, I've summarized some practical tips for judging distances in rearview mirrors, which are quite simple and effective. For instance, in the interior rearview mirror, if the vehicle behind appears as a small dot, it means it's at least 50 meters away—no need to worry. If it occupies half the mirror, the distance is likely around 20 meters, and you should slow down immediately to avoid a rear-end collision. As for the side mirrors? When you can see the entire front part of the vehicle behind you, the distance is roughly 30 to 40 meters; if only a small portion of the headlights or tires is visible, it's within 10 meters—too close and prone to accidents. I recommend adjusting the mirror angles so the horizon sits at the mirror's midline to minimize blind spots. While driving, you can also use roadside markers or buildings as reference points, such as comparing changes in the trailing vehicle's position to improve judgment. Safe driving is paramount—avoid sudden braking and maintain space to give the trailing vehicle time to react.

[DeClayton]

When I first started learning to drive, I also often worried about this. There are some tricks to judging the distance between cars. In the rearview mirror, when the image of the following car is as small as a model, it means a long distance; when the image becomes larger and clearer, it means the distance is shortening. For example, when you can clearly see the license plate number, the distance is already quite close. As for the side mirrors, if you can see the complete front part and a corner of the following car, the distance is estimated to be over 40 meters; if only a small part of the car is visible in your mirror, it might be in your blind spot. In this case, you must turn your head to confirm before changing lanes. Don’t just rely on guessing—practice more on open roads and combine it with changes in speed to estimate. For example, when a car is catching up quickly, you can slow down appropriately to let it pass. Beginners are most afraid of blind spots, so develop the habit of checking if the mirrors are clean and properly adjusted every time you get in the car. With time, driving will become more natural.

[MacMary]

From a safe driving perspective, accurately judging vehicle distance via rearview mirrors is crucial for accident prevention. The size of the following vehicle's image in the interior rearview mirror directly indicates proximity: smaller means farther, larger means closer. Typically, when the image occupies one-third of the mirror, the distance is approximately 30 meters, requiring heightened alertness. In side mirrors, if the following vehicle is positioned toward the outer edge with its front half visible, the distance is safe; entering blind spots or only partial visibility indicates danger. I recommend drivers regularly adjust mirror angles and establish speed-distance rules, such as the two-second following rule: maintain at least a two-second gap between fixed points on your vehicle and the one behind. Remember, misjudgments frequently occur in rainy or foggy conditions—always clean mirrors to enhance visibility clarity.