Relationship between Programmed Heavy Vehicle Inspections and Traffic Safety

Heavy vehicle crashes incur significant economic and social costs. Although most crashes are considered to be related to driver error, the effects of vehicle defects are major in many crashes. Therefore, various vehicle inspections including Queensland's Certificate of Inspection (COI) scheme have been implemented to improve the safety of heavy vehicles. This study analyzes the trends of heavy vehicle crashes and their relationships with COI results. Longitudinal data provided by Queensland's Department of Transport and Main Roads for the period of June 2009 through December 2013 were used to perform the analyses. The data include 474,640 programmed inspections and 2,274 crashes in which heavy vehicles were involved. The results show significant relationships between the monthly average inspection failure rate as well as the monthly average failure severity level, and the total number of heavy vehicle crashes. The results also reveal significant relationships between the monthly average inspection failure rate, average vehicle age, as well as monthly average mean maximum temperature, and the number of defect-related crashes. The implications of these results are discussed with respect to heavy vehicle safety policies.