How to judge the 30cm distance between the car and the line using rearview mirrors?

[McJune]

Most methods involve dividing the car into three equal parts, aligning the outer one-third of the front hood with the right sideline while driving. From the driver's seat view, when the raised portion of the left wiper aligns with the right sideline on the ground, the car body is approximately 30cm away from the right edge. Through the right rearview mirror, observe the front door handle - when it appears tangent to the right sideline, the distance between the car body and the right road edge is roughly 30cm.

[McMatthew]

Last time I accompanied my friend for the Subject 2 driving test, the instructor taught a super practical trick: adjust the distance between the vehicle and the sideline by observing the door handle position through the right rearview mirror. Keep the outermost edge of the door handle aligned with the top of the sideline, which is roughly 30 centimeters. Different car models may require slight adjustments. Another classic method is aligning the raised part of the wiper with the sideline, but don’t rely too much on a single reference point—using the auxiliary lines from the reversing camera is more accurate. During practice, draw lines with chalk and step out to compare a few times to build muscle memory. By the way, the cleanliness of the rearview mirror is crucial; remember to apply anti-fog spray on foggy days.

[IvanAnn]

As a driving school instructor, I often see students struggling with the 30-centimeter issue. The key is to develop spatial awareness: after adjusting the seat upright, observe the gap between the car body and the sideline in the rearview mirror from the driver's position. When the car body occupies one-third of the mirror and the sideline occupies two-thirds, the distance is approximately 30 centimeters. Remembering this visual ratio is more reliable than measuring. Make small steering wheel adjustments during correction. I recommend downloading the VR simulation from the driving test app for more practice. By the way, differences in tire pressure can affect the car's height, so remember to check it regularly.

[DelAlessandra]

An old driver taught me this practical trick: Lower the window to observe the position of the right front wheel. When the wheel rim is two fingers' width from the sideline, the rearview mirror is exactly 30 centimeters away. This method requires getting out of the car repeatedly to verify and form a visual memory, which becomes intuitive later. At night, you can use a phone flashlight to illuminate the line, and in rainy weather, applying a waterproof film on the rearview mirror makes it clearer. A reminder for beginners: don't keep turning your head to look at the rearview mirror the whole time—just glance to confirm. Safety first.