This paper contains part of the results of a repetitive and comprehensive analysis of accidents among bus drivers. In a series of articles different aspects of the aetiology of bus drivers' accidents will be highlighted. The results presented indicate a strong negative association of experience with accident risk, modified to a certain extent by age. The suggested interaction between accident liability, age and experience warranted more detailed attention to the first few years of employment, revealing systematic differences between groups of drivers of different age groups but with comparable experience: younger drivers had higher accident rates than older ones. An increase of accident risk during the second year of employment after an initial decline could be detected in the younger group of drivers; the older group only showed a continuous decline.