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-barrier rule Two-barrier rule The two barrier rule is a policy of safety for work on piping carrying high pressure and/or high temperature fluids. It is commonly used by oil companies. The rule simply states that for any work that must be done on a section of piping, which involves breaking containment, there must be at least two barriers separating the fluids from the broken area. The purpose behind specifying two barriers is to ensure redundancy. The risk of a total loss of containment is reduced if there are two independent isolations as it is highly improbable they would both fail at