Differential accident involvement of bus drivers

The relations between 552 bus drivers' low-speed traffic incidents (without consideration of culpability) and their age, exposure (hours of work) and experience (years as a bus driver) were calculated using bus company data from the Swedish city of Uppsala for the years 1999-2003. It was found that risk decreases with age and experience, with experience as the strongest factor, carrying the effect. Exposure (hours worked) had a curvilinear association to accidents. Also, the use of accidents per work hour yielded more easily interpreted results than the absolute number, indicating the importance of taking exposure into account when predicting accidents. These results are mainly in agreement with previous studies on other road user groups. However, two different ways of calculating age effects (individual and group level) gave somewhat different results, indicating that a fairly popular method of calculating risk indexes may be faulty. Furthermore, time for holding a car driver's license did not influence bus accident liability, despite being strongly correlated with age, indicating that bus driving is separate from car driving experience. Also, the extremely small amount of variance accounted for by experience and age point to the importance of other factors, although there seem to be a strong effect during the first years of driving, which thereafter levels off.