The rule of seconds: Calculating safe following distances

When you see an accident on the road ahead, it will take you about 1.5 seconds to react. Then, a typical car requires 1.5 seconds to brake. That means you should keep at least 3 seconds of distance between you and any vehicle in front of you, and perhaps more depending on driving conditions.

tractor-trailer rule of secondsThe “rule of seconds”can be found in the Virginia Commercial Driver’s Manual, which contains information all truck drivers must know to pass their exam for a commercial driver’s license (CDL). The rule of seconds advises that if you’re driving below 40 mph, you should maintain at least one second of distance for each 10 feet of vehicle length. Over 40 mph, add an extra second.

For a truck driver cruising in a longer, heavier vehicle, more space and time is needed. For example, if driving a 60-foot vehicle at speeds over 40 mph, you should leave seven seconds between you and the vehicle ahead. You arrive at this number by calculating one second for each 10 feet of vehicle length plus an additional second for safety, a total of seven seconds.

For a typical car, we can replace calculations with a good rule of thumb: allow at least 3 seconds between you and the car in front of you. If you’re in a large SUV, you may want to add an extra second.

Here’s how to apply the Rule of Seconds:

  • Watch the vehicle ahead pass a fixed point, such as an overpass, sign, fence or other marker. Be careful not to fix your attention on it.
  • Begin counting off the seconds it takes you to reach the same place in the road.
  • If you reach the mark before you have counted off the correct number of seconds, you’re following too closely. Slow down and increase your following distance.

The most common car accidents are rear-end collisions. Such accidents are often caused when drivers do not have enough time to react safely to slowing or stopped traffic, meaning they were following the car in front of them too closely. Watch this travelers’ video to see how it works. As you’ll see, time matters even more than space when it comes to safe driving.

Stopping distance is what it will take to come to a full stop in an emergency, and is determined by your reaction distance and your braking distance. The reason the three-second rule works, no matter your speed, is that as your speed increases, the distance between you and the car ahead of you needs to increase to allow for a safe stopping distance.

The rule of seconds requires an increase when it comes to snow, ice or heavy rain. The 3-second rule may need to be extended to 4, 5, or even 9 seconds.

As you head out for the highway, give yourself extra time to get where you’re going. This will reduce the temptation to speed and tailgate. Follow the rule of seconds to give yourself more space and safety; it’s as easy as 1-2-3.

If you have been injured in an auto accident through no fault of your own, an experienced attorney can help you navigate next steps. Call Allen & Allen today, at 866-388-1307.