Three car lengths – that’s how far you should stay behind the vehicle in front of you.
That distance, about five meters, will give you enough time to react safely to hard braking or quick lane changing. Staying three car lengths behind the vehicle in front of you will also help you avoid any rocks or road debris kicked up by the vehicle in front of you and prevent damage to your windshield. However, if the vehicle in front of you is larger than a passenger vehicle, such as a semi-truck or an ambulance, three car lengths isn’t enough of a buffer.
According to the Federal Motor Carrier Safety Administration, the average stopping distance for a loaded tractor-trailer traveling at 88kph in ideal conditions is 60 meters, as compared to 40 meters for a passenger vehicle. So when you’re traveling behind a large truck, increase your following distance to seven car lengths, or about 35 meters.
In rainy or snowy conditions, double your following distance.