What Changes Occur in Nighttime Visibility Distance?
3 Answers
Nighttime visibility distance becomes shorter. Here are the relevant explanations: 1. Reason for reduced visibility distance: At night, while driving on the road, due to the effect of headlights, bright objects are seen against a dark background, making them appear larger. However, the eyes still judge distance based on the perception that closer objects appear larger, resulting in reduced visibility distance. 2. Field of vision: Motor vehicle drivers can only clearly see objects illuminated by the headlights. The high beam of a car typically illuminates up to about 150m, while the low beam covers about 30m, with the illumination generally not extending beyond the road surface. Objects beyond this distance and range cannot be seen clearly.
As a truck driver who frequently drives at night, I have a deep understanding of the changes in nighttime visibility. During the day, I can easily read road signs 200 meters away, but at night, even with headlights on, I can barely identify objects within 80 meters. Especially on rainy days, the windshield reflects the lights from oncoming vehicles, turning my vision into a blurry whiteout. Driving on provincial roads without streetlights, the occasional stray cats or dogs darting out always make me slam on the brakes. When I was younger, I didn’t notice it as much, but now, nearing fifty, I have to wear blue-light-blocking glasses for highway driving at night, or my eyes start aching after just two hours. Ultimately, effective nighttime visibility is roughly only one-third to half of daytime visibility, so road condition anticipation must be done earlier, and speed should be reduced by at least 20% compared to daytime driving.
Last week, I took trainees for night driving practice and specifically reminded them to pay attention to changes in visibility. Urban areas with streetlights are manageable, but suburban roads are risky: LED headlights can only illuminate about 100 meters, while the braking distance requires over 40 meters. Curves are even more dangerous, as headlights can't illuminate the inside of the turn. Interestingly, trainees often complain about eye strain—this is because nighttime pupil dilation increases light intake but reduces depth perception. Now, I teach them techniques like using reflective road edges instead of focusing on the road surface and maintaining a following distance of over four seconds. Oh, and electric bikes suddenly darting out from under trees are the deadliest—visibility in these shadowed areas is nearly zero, so slowing down in advance is a must.
