Abstract
Traffic safety studies have clearly shown that the cause of the majority of traffic accidents is human error. A number of factors play a significant role in the production of human errors, one of which is the influence of alcohol and drugs. In order to ascertain the effect of alcohol and drugs on traffic safety it is necessary to examine the problem from a number of perspectives. Epidemiological studies, laboratory tests of driving related skills, simulator studies and on-road studies each provide a vital part of the evidence establishing the role of any given substance to traffic safety.