Impact of truck safety programs on accident reduction

Truck safety has become an ever present issue for road travelers today. In an effort to manage the trucking industry and reduce accidents involving trucks, truck safety inspection programs under the Motor Carrier Safety Assistance Program (MCSAP) were implemented in all fifty states and five territories. It was the goal of this report to determine whether these safety inspection programs reduce accidents. The scope of this paper included a literature review of previous research, analysis of the Tennessee truck accident data for 1989 through 1994, discussion and presentation of the results of this analysis, and presentation of the results of a MCSAP survey. Several approaches were used to evaluate these safety programs and their effects on accidents. Accident data and truck safety inspection information from the state of Tennessee were collected. The raw accident data were analyzed using regression analysis and a nonparametric quasi-experimental time series analysis. The accident data were then normalized using various exposure methods including a quasi-induced exposure method and a seasonal factor method. Then the normalized data were analyzed using a simple regression analysis, a twelve period moving average method, and a before and after study using extrapolation methods. The normalized data were also compared to enforcement efforts and analyzed when broken down into facility type classifications. The findings of these analyses were as follows: if the data are analyzed without considering exposure, truck accident involvements appear to have certain reductions and increases of involvement at certain times of the year. However, if the data are analyzed taking exposure into account, the conclusion could be made that truck safety inspection programs do not reduce or increase accidents. The results of the time series analysis on the raw data further supported this conclusion and disproved the apparent trends from simple regression. Statistically, there was no significant increase or decrease in accident involvements from one month to another when months of "special interest" were analyzed. No trends were apparent when the data were analyzed while classified into facility types. No correlation was found when the normalized data were compared to enforcement, i.e., the level of enforcement does not increase or decrease the number of accidents. The overall conclusion was that neither a reduction nor increase in accidents from truck safety inspection programs could be proven with the available data and methods of analysis used.