Data has been collected from a random sample of motorcycles and their riders and a structured sample of drivers using postal questionnaires, to determine the relationship between the accident liability of these riders/drivers and variables such as age, driving experience, sex, socio-economic group (SEG) and annual mileage. Generalised linear modelling techniques have been used to develop statistical models which will predict the accident liability - the expected number of accidents per year, corrected in the case of drivers for memory loss - for an individual rider/driver as a function of relevant explanatory variables. The key implications arising from these surveys may be arised as follows: (i) accident liability is dependent mainly on exposure (total annual mi02age), the driver's age and his or her driving experience measured as the number of years since passing the test; (ii) predicted accident frequencies are not directly proportional to annual mileage; (iii) the proportion of driving on different types of road (built-up, rural and motorway) does influence accident liability, but to a lesser extent than age and experience. In the case of motorcyclists, the type of road effect is confounded with bike size such that on open roads, riders of big bikes (engine capacity >500cc) had fewer accidents than those riding smaller bikes. Seasonality is also an important factor for motorcyclists as is the proportion of driving in the dark for car drivers; (iv) the form of the age effect means that the proportional change in liability with increasing age is larger for younger riders/drivers than for older riders/drivers. No upturn of accident frequency for older drivers could be detected; (v) the form of the experience effect means that accident involvement falls rapidly after passing the test - i.e. The learning curve is steep in the early years; and (vi) interactions were found between the accident liability-age/experience relation and sex and seg for car drivers, and between the accident liability relation and sex and mileage driven in a car for motorcyclists. The analysis showed that young males have a higher accident liability than young females in cars or on bikes. The effect of car driving on the accident liability of motorcyclists suggests that the road safety skills acquired whilst driving a car were equally effective when taking up bike riding.
Abstract