Effects of Heavy-Vehicle Mechanical Condition on Road Safety in Quebec

Abstract

A 2-year study was conducted of the effect of heavy-vehicle mechanical condition on road safety in the province of Quebec, Canada. The results in this summary include an evaluation of the effect of an existing annual heavy-vehicle mandatory mechanical inspection program (MMIP) on road safety and its effectiveness in improving heavy-vehicle mechanical condition. The effect of various mechanical components on road safety and the importance of their periodic inspection also are analyzed. Among the main findings were ( a) heavy-vehicle mechanical condition is responsible for 10 to 20 percent of accidents involving this type of vehicle in Quebec; ( b) if older vehicles (12 years or more) are not taken into account, the MMIP seems to prevent accidents caused by mechanical defects for a subsequent period of 2 to 3 months; ( c) the MMIP is not fulfilling its mandate adequately, because the observed frequency of heavy vehicles with noncomplying mechanical components is high, independent of the elapsed period since the last MMIP; ( d) heavy vehicles affected by major noncomplying components have a propensity to be involved in accidents that is five times higher than that of complying vehicles; ( e) the braking system is the most affected by major noncomplying components; ( f) the braking system comes in first when the dangerousness of mechanical components is considered, followed by tires, chassis, and steering system; ( g) the inspection program is not equally effective in identifying defect locations; ( h) heavy vehicles are responsible for 46 percent of the accidents in which they are involved; ( i) pretrip inspections appear to be the ideal complement to the MMIP in preventing accidents caused by mechanical defects. Based on these findings, recommendations are made on the inspection program, the data, and braking system maintenance to improve the mechanical condition of heavy vehicles and to reduce accidents caused by mechanical defects.