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-man rule captain left to use the toilet. Two-man rule The two-man rule, also known as the four-eyes principle, is a control mechanism designed to achieve a high level of security for especially critical material or operations. Under this rule all access and actions require the presence of two authorized people at all times. Per US Air Force Instruction (AFI) 91-104, "the two-person concept" is designed to prevent accidental or malicious launch of nuclear weapons by a single individual. In the case of Minuteman missile launch crews, once a launch order is received, both operators must agree that it is valid by