This paper presents: (i) an operational definition of risk exposure, (ii) a questionnaire developed to measure exposure, (iii) validity studies of estimates of the distance travelled and time spent driving for different permit holder categories, and (iv) a feasibilitystudy of the cost effectiveness of a telephone survey on exposure. The categories of drivers used for the validation studies were as follows: 1. Long distance lorry drivers. In these studies, the distance travelled and time spent driving by some of the drivers contacted was compared with data registered in the company logbooks. 2. Urban bus drivers. In these studies, the interview was conducted on the bus. Information provided by the drivers was checked against mileage travelled during one day calculated from data obtained from the Transport Commission. 3. Private car drivers. These were 32 coworkers, friends, and relatives of the researchers. With these, estimated mileage and time for one week obtained by questionnaire were compared with logbook registered time and odometer readings of the subsequent week. The results indicate that the method used is practical. However, the validity of the exposure parameters used depends on the individual driver class. Phone surveys were found to be cost effective.
Abstract