Allowing yourself proper following distance between your car and the car ahead of you can be difficult to visually estimate. A good way to gauge a suitable gap is to use the “Three-Second Rule.” Here’s how it works: when the car or truck in front of you crosses a certain fixed object on the side of the road (like a sign or tree), start counting, “one thousand one, one thousand two, one thousand three.” You should not cross that same point for three seconds. Under normal conditions it takes about 2-3 seconds to completely stop when traveling at speeds between 35 mph to 65 mph; so with a three-second space cushion, you should have enough time to react and brake when something happens up ahead.
Sometimes you may need to add additional space to the following distance calculation. Here are some scenarios where extra room is required and you should allow for a following distance of four or more seconds:
- If the road or weather conditions are bad. For example, braking distance doubles on a wet road.
- If you are being tailgated. If a driver is following too closely you should slow down and increase your following distance so that you will have more time to react if the car in front of you is forced to suddenly stop.
- If you are towing a trailer or have additional weight in your vehicle. The added weight will increase your vehicle’s stopping distance.
- If you are following a motorcycle. A motorcycle can stop quicker than a car. Give yourself extra space in front of your vehicle so you have adequate time to stop.
- If your vision is blocked or visibility is poor. When your view ahead is blocked, for instance when you are behind an 18-wheeler or large van, you will have less of an idea of hazards further down the road. Leave yourself more space to increase your reaction time.