This report presents the results of two surveys - an interview survey of about 1000 HGV drivers and a postal questionnaire survey of just over 4600 male drivers aimed at exploring the relationship between accidents and daytime sleepiness. Drivers in this survey provided details of the accidents they had experienced in the last three years, and car drivers identified those factors they thought contributed to the accident. In addition to the normal demographic and exposure variables - age, annual mileage, and the proportion of time spent driving on different types of road - drivers completed the Epworth scale measuring daytime sleepiness; car drivers also reported whether they had felt close to falling asleep whilst driving during the past 12 months and whether the car they drove most was privately or company owned. In the case of car drivers, the analysis of this data has enabled the characteristics of tiredness-related accidents to be compared with the characteristics of all reported accidents. The probability of feeling close to falling asleep at the wheel has been quantified in terms of the demographic and exposure variables and Epworth score using a logistic model. Car drivers reported that about 7 per cent of accident involvements were associated with tiredness (about 9-10 per cent of accidents). The accident liability of both the HGV and the car drivers has been quantified using a multivariate statistical model; for some drivers accident liability is shown to be sensitive to daytime sleepiness. (A)
Abstract