The relation between motor accident mortality and compulsory vehicle inspection is examined by regressing age-standardized mortality ratios on inspection and other variables across states. The adjusted coefficient of multiple determination is typically about 0.85. Inspection is negatively related to mortality, but the net effect of inspection is less than one third as large as the gross difference between states that require inspection and those that do not and does not generally differ from zero at high levels of statistical significance. The effect of inspection appears to be greater in states with more than one annual inspection. It is greater in low income than in high income states, and greater in high education than in low education states. Dollar estimates of the benefits of inspection are found to exceed estimated costs; the difference, however, is not as large as is often alleged.
Fuchs VR, Leveson I. Motor Accident Mortality and Compulsory Inspection of Vehicles. JAMA. 1967;201(9):657–661. doi:10.1001/jama.1967.03130090021005