The one aspect that prevents a crash from occurring is keeping space around the vehicle. The importance of the two-second rule is emphasised, with reference to the UK Highway Code and DSA driving manuals. Underestimating stopping distance is a major problem among drivers. The correlation between travelling speed and stopping distance is discussed. The driver must be able to see the hazard and his brain must compare the viewed scene with past experience in order to decide what to do. In the Highway Code, this thinking time is given a nominal duration of 0.7 seconds, less than times given in other countries. The third factor is Muscular Reaction Time, the time taken to move the foot from the accelerator to the brake. The variables associated with braking and brake time are discussed: type of wheel, vehicle weight, and road conditions. The two-second rule gives a reaction time and works at all speeds above 6mph with no maximum limit. Below 6mph, the Queuing Distance Rule is used. The two-second rule is for ideal conditions and further time is required for braking in non-ideal conditions. A table is given of the additional time required in non-ideal conditions.
Samenvatting