Defective equipment contributes to between 7 and 16% of heavy truck accidents, with defective brakes being the largest contributor. In January 1980, the Washington State Patrol (WSP) began a program to inspect heavy trucks. The WSP's Commercial Vehicle Enforcement Section assigned five two-man inspection teams to three weigh stations on Interstate 5, the main north-south route through the most populated region of the State. Over the 18 months of the program, the five teams inspected 18,803 heavy trucks and placed 11,085 out of service for equipment violations. Brake adjustment violations (34.4%) and brake component violations (17.8%) were the major violation categories. Data collected through the inspection process were analysed to see if a downward trend in the proportion of trucks with defects occurred during the course of the program. Heavy truck accident data were also analysed to see if defect-involved accidents declined after program implementation. The accident data analysis compared data before and during the program, defect-involved and nondefect-involved accidents, and Washington with two other states. Both brake defect and nondefect accidents declined in Washington over the period of the program. In addition, both types of accidents declined during the same time period in the two comparison states, suggesting a general decline in truck accidents. Therefore, it could not be concluded that Washington's decline in brake defect accidents resulted from the inspection program. Although the inspection data showed a significant decline in the percentage of intrastate trucks with brake component defects, this could not be considered conclusive evidence of program impact because of possible sampling bias. Suggestions are offered for other states that have inspection programs.
Abstract