Two-second rule two seconds as inadequate, and recommend a three-second rule. German law requires a minimum 0.9 second distance but when tested under relaxed conditions researchers found that their test subjects spent 41% of the test time at following distances under 0.9 second. The United States National Safety Council suggests that a three-second rule—with increases of one second per factor of driving difficulty—is more appropriate. Factors that make driving more difficult include poor lighting conditions (dawn and dusk are the most common); inclement weather (ice, rain, snow, fog, etc.), adverse traffic mix (heavy vehicles, slow vehicles, impaired drivers, pedestrians, bicyclists, etc.), and
Two-second rule Two-second rule The two-second rule is a rule of thumb by which a driver may maintain a safe trailing distance at any speed. The rule is that a driver should ideally stay at least two seconds behind any vehicle that is directly in front of his or her vehicle. It is intended for automobiles, although its general principle applies to other types of vehicles. Some areas recommend a three-second rule instead of a two-second rule to give an additional buffer. The two seconds is not a guide to safe "stopping" distance, it is more a guide to reaction times. The