To obtain information from drivers about fatigue or sleepiness as a factor in accidents, the Transport Research Laboratory (TRL) conducted two surveys: (1) an interview survey of male heavy goods vehicle drivers; and (2) a postal questionnaire survey of male car drivers. The surveys were designed to determine the relationship between accident involvement and a driver's tendency to daytime sleepiness as measured by the Epworth Sleepiness Scale (ESS). In the first survey, just under 1000 drivers were interviewed, but no statistically significant relationship was found between accident frequencies and annual mileage or proportion of driving time on motorways, and accident frequencies were much higher for younger drivers. In the second survey, just over 4600 responses were received from a structured sample of 9000 drivers. The drivers reported that tiredness contributed to 7% of accident involvements, the equivalent of 9-10% of accidents.
Abstract