What are the regulations for safe following distance?

[Gabriela]

There is no absolute standard for safe following distance, only dynamic standards. The most direct and important factor affecting safe following distance is vehicle speed. When the speed increases, the required braking force, braking distance, and the distance traveled at the original speed during the reaction time all increase accordingly. According to the laws of mechanics, a vehicle will continue to move forward for a certain distance during the time it takes to come to a complete stop from motion. If the following distance is too close, it is very easy to collide with the vehicle in front, causing a rear-end accident. To ensure that the following vehicle will not rear-end the vehicle in front under any extreme circumstances, the following vehicle must always maintain a certain distance from the vehicle in front, leaving enough braking space in case of emergencies. When the speed is above 100km/h, the safe following distance should be more than 100 meters. When the speed is above 60km/h, the safe following distance should be numerically equal to the speed. When the speed is around 50km/h, the safe following distance should not be less than 50 meters. When the speed is below 40km/h, the safe following distance should not be less than 30 meters. When the speed is below 20km/h, the safe following distance should not be less than 10 meters. On highways, each dashed lane divider line is 6 meters long, and the distance between lines is 9 meters, making a total of 21 meters for two white lines plus the space in between. Drivers can use this method to easily estimate the following distance.

[SanSerenity]

The regulation of safe following distance while driving is primarily based on time. I usually refer to the 'three-second rule': pick a roadside marker, start counting 'one second, two seconds, three seconds' when the car ahead passes it. If my car hasn't reached the same point by the count of three, then it's a safe distance. This is a common recommendation in driving regulations to help avoid rear-end collisions. The specific distance depends on speed—for example, at 100 km/h on the highway, you should leave over 100 meters because the reaction time is at least two seconds, including braking time. I've seen many accidents caused by following too closely, so even in heavy traffic, I insist on maintaining distance to give myself buffer space. Additionally, double the following distance in bad weather; rain or snow makes roads slippery, doubling braking distance. The general principle is to leave enough time to handle sudden situations—it's not a rigid rule but a key to protecting yourself and others. Developing this habit can significantly reduce risks, and I recommend beginners practice more to get a feel for the rhythm.

[VonIsabel]

I find judging the distance between cars in actual driving quite simple by using the three-second rule: pick a reference point like a billboard, count to three when the car ahead passes it, and if I haven't reached it by then, it's safe enough. But the distance should be flexible—I adjust it based on speed. In the city, 20-30 meters is sufficient at slow speeds, while on the highway, at 60 km/h, at least 40 meters is needed. Many factors affect this, like worn tires slowing braking, so I leave extra space. In rain or fog with poor visibility, I extend it to a four-second gap. I also check the rearview mirror frequently to ensure no car is tailgating. Maintaining a safe distance reduces driving stress, especially on long trips. When I first started driving, I neglected this and nearly had an accident—now I understand it's a fundamental safety skill.

[OJayce]

The essence of safe following distance lies in physics principles: typical reaction time is 1.5 seconds plus one second for braking, with total distance being proportional to the square of speed. I always emphasize maintaining about 64 meters gap when driving at 80 km/h on highways. Keeping sufficient space reduces rear-end collision probability, as accidents often occur due to inadequate buffer. This distance should increase in deteriorating weather conditions - my data analysis shows rain/snow increases braking distance by over 50%. Vehicle conditions like aging brake systems also require additional buffer. The key is allowing time to handle unexpected situations.