The Association of Accident Severity and Frequency with Vehicle Age*

INTRODUCTION "DETERIORATION OF a vehicle with time is inescapable, whether from normal wear, abuse, defective construction, improper maintenance, poor quality of original or repair parts, inadequate skill of mechanics or other factors. With the deterioration of such components as brakes, steering systems, and tires, the chances of the vehicle becoming involved in a crash increase." This assertion was made by the Secretary of Transportat ion in his July 1968 report to the Congress (1968) and it reflects the intuitive approach taken by some highway safety advocates. They believe vehicle aging leads to deterioration and that deterioration makes older vehicles, compared with new ones, more prone to crashes and more susceptible to damages when crashes occur. As a result of both, they argue, older vehicles contribute disproportionately to highway losses. Since the recommendations of the above report will influence highway safety countermeasures, it is important that the underlying hypotheses be carefully investigated. At the time this study was begun (more than a year before the Secretary's report was released), this question was asked: Are measurable crash phenomena associated with aging, and, if so, how may these be influenced by countermeasures such as motor vehicle inspection? Since past studies did not adequately examine the questions, this project was designed to investigate certain relevant factors in more detail.