Exposure estimates are used in highway safety studies as a measure of the opportunities for traffic accidents to occur. Typical exposure measures for traffic accidents include the number of sites considered, the duration of the time period for which traffic accident data are analyzed, the total length of the sites, or the total vehicle kilometer of travel on those sites, etc. The greater the exposure effect, the greater the number of traffic accidents that would be expected to occur. Thus, safety measures used in traffic accident surveillance often combine both traffic accident and exposure measures for given time period into a traffic accident rate. Traffic accidents form the numerator and exposure forms the denominator of the traffic accident rate expression. This paper analyzes the exposure effect on traffic safety, and presents a criteria for evaluating those effects. (A)
Abstract