How to Judge the Distance When Seeing a Car in the Rearview Mirror?
2 Answers
When judging the distance of a car through the rearview mirror, the general rule of thumb is: the smaller the following car appears, the safer it is. If the following car occupies 1/3 of the mirror, the distance is about 10 meters. If it occupies 1/2 of the mirror, the distance is approximately 7 meters. If the following car fills the entire mirror, the distance is about 3 meters, which is not suitable for turning. Below are specific methods for observing distance through the rearview mirror: 1. When looking at the rearview mirror: The driver should divide the rearview mirror into "inner" and "outer" sections. Whether it's the left or right rearview mirror, the half closest to the driver is designated as the "inner" section, and the half farther away is the "outer" section. This method applies to judging vehicles on either the left or right rear side. 2. Drivers should understand that if the following car is closer, it will appear smaller and closer to the outer section of the rearview mirror. Conversely, if the following car is farther away, it will appear more complete and closer to the inner section. Generally, if the following car is at the boundary between the inner and outer sections of the rearview mirror, the distance is about 25 meters. 3. Drivers can also estimate the distance to the following car using the interior rearview mirror: If only the hood of the following car is visible and the grille is not, the distance is about 3 meters. If the grille of the following car is visible, the distance is approximately 8 meters. If the entire wheel of the following car is visible, the distance is more than 20 meters.
I've been driving for over twenty years, and judging the distance of the car behind me through the rearview mirror relies entirely on accumulated experience. The mirror is convex, making objects appear smaller and curved, so if the car behind looks small, it's far away—about 50 meters or more. If it fills the entire edge of the mirror's view, the distance is likely less than 10 meters, which is too close. When driving at high speeds, the distance changes quickly, so I maintain a safe following distance and use the three-second rule with reference points for assistance. At night, the brightness and size of headlights can also help with judgment, but don’t rely solely on the mirror—turning to check blind spots is a must. With enough practice, intuition becomes accurate. For example, in city traffic jams, frequently observing changes in the mirror helps develop habits that reduce the risk of rear-end collisions.
