This report describes three experimental studies, undertaken for the Highways Agency, in which the role of driver characteristics in three specific components of the driving task - speed choice, emergency braking and overtaking - have been explored. The purpose of the work was to provide the design engineer with more detailed insights into the types of driver using the roads and their performance in critical situations. A simple stratification of car drivers based on age and annual mileage has been developed from speeds measured at a sample of trunk road sites in Great Britain in combination with the personal characteristics of the drivers obtained by postal questionnaire. The self-reported accident liabilities of these drivers has also been related to their individual characteristics and an association obtained between drivers' speed choice and their accident liability. The emergency stopping study explored the determinants of emergency stopping performance using a simple simulator. Analysis of this data showed that emergency response times are dependent on the characteristics of the drivers. Overtaking behaviour on single carriageway roads was studied both in a simulator and on the road. Logistic modelling showed that the probability of a driver accepting an overtaking opportunity was related to variables such as gap size, overtaken vehicle speed and the personal characteristics of the drivers. The differences in emergency response times and in the overtaking requirements of drivers classified by the age and mileage groupings devised in the stratification study are given in the report. (A)

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