How to judge the 30 cm distance in straight-line driving?

[DiJasper]

In straight-line driving, the 30 cm distance can be judged by observing the left reinforcement rib of the car hood, the left wiper, the one-third point of the car hood, or the door handle in the rearview mirror. Here are the specific methods: Observe the left reinforcement rib of the car hood: This refers to the raised line on the left side of the car hood. When the left reinforcement rib aligns with the center of the lane, the distance between the car body and the sideline is approximately 30 cm. Observe the left wiper: Align the raised part of the left wiper with the white line on the right side of the ground, and then confirm by checking the right rearview mirror.

[VanCassandra]

Judging a 30 cm distance while driving is quite practical. I also struggled when first learning to drive, but now I can manage with a few simple reference points. For example, observe the right-side road edge line and keep the car body parallel to it. When viewing from the rearview mirror, if the line is about one finger's width away from the wheel, that's roughly 30 cm. Alternatively, check the door handle position—when the edge of the handle aligns with the curb, it's approximately correct. Another method is to park in an open area, step out, and measure the actual distance with a ruler, then memorize the visual feel of the car's front or wheels. With practice, it becomes second nature—especially useful for driving tests to avoid scraping tires against curbs. Beginners shouldn't rush; focus on observing the relative position between the car body and road markers while driving slowly to build experience.

[LillianMarie]

I usually rely on my intuition when driving. For the 30 cm distance, I just check the distance between the road shoulder line and the wheel in the right rearview mirror. If the line appears very narrow and close to the wheel, it means I'm too close; leaving a gap about the size of a fist is just right. I also glance at the wiper node—if it aligns with the roadside, it's roughly 30 cm. This trick is handy for narrow city roads or parking. Remember to keep the car body straight and hold the steering wheel steady without unnecessary adjustments. Before parking, you can slowly adjust the distance to avoid stepping out to measure. Once it becomes a habit, it's almost instinctive. But be extra careful during rainy or snowy days when visibility is poor—safety always comes first.

[JaxonAnn]

The best way to judge 30 centimeters is to use the rearview mirror as a reference. Keep your head still while driving, and look at the curb or marking line at the bottom of the right rearview mirror. The gap between the line and the wheel is the target range. The standard is to leave about three to four fingers' width, which may vary depending on the car. Additionally, observe the position of the door handle or align the edge of the co-pilot's dashboard with the roadside. At first, you can practice by parking a few times, pulling the handbrake, getting out to measure, and confirming your visual memory. Is this required for a driver's license? Yes, during the road test, you must park by the roadside without exceeding the limit. Practice more, and your body will quickly memorize the position.

[VanHolden]

When judging the 30cm distance while driving, I recommend focusing on reference points between the vehicle body and the ground. When aligning the outer edge of the right wheel with the curb or road markings, pay attention to the visual parallax of wheel position, maintaining about half a fist's space. Approach slowly before parking, making slight steering adjustments to keep the vehicle moving straight. Beginners often rush, resulting in wheels scraping curbs and damaging rims. Be extra cautious during rain or at night - if poor lighting makes reference points unclear, stop to verify. For safety, don't force it; if unsure, get out and check. Mastering distance control makes parallel parking and reverse parking much easier.

[VonSabrina]

To gauge a 30cm distance, focus on a few visual cues. I typically watch the curb line in the rearview mirror and the gap between the wheel and curb—about 2-3cm clearance is ideal. Another method is aligning the edge of the driver’s door handle with road markings like curbs or lane lines; if they match, the distance is roughly accurate. Beginners should practice parking repeatedly in quiet areas—hands-on experience trumps theory. Remember not to get distracted while the vehicle is moving; just glance briefly at mirrors or door handles. Regularly driving on narrow urban roads helps build spatial awareness of the car’s width. With time, it becomes instinctive, preventing rim scrapes during parking.