Bounds on effectiveness of driver hours-of-service regulations for freight motor carriers Randolph W. Hall * , Aviroop Mukherjee Epstein Department of Industrial and Systems Engineering, University of Southern California, Los Angeles, CA 90089-0193, United States Abstract Crash rates for trucks depend in part on the length of time drivers have been operating their vehicles. This paper inves- tigates bounds on the reduction in crash rates due to the imposition of hours-of-service regulations, which limit the number of hours drivers operate their vehicles. Methods for analyzing probability distributions for trip length, and odds ratios for crashes (as a function of hours driven) are developed. We also produce bounds on the economic costs of truck-involved collisions, and estimate changes in these costs due to changes in hours-of-service rules. The study is a first step toward a broader cost/benefit analysis of regulations, based on analysis of data from the fatal accident reporting system (FARS). Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Trucks; Safety; Hours-of-service; Bounds; Regulations; Motor carriers 1. Introduction Safety is a critical concern for the freight industry. The National Highway Traffic Safety Administration reported in its annual 2002 traffic safety report that tractor-trailers constitute only 3% of the registered vehicles operating in the United States but are involved in almost 10% of all fatal vehicle crashes. Fatigue, alcohol abuse, human negligence, and sleep deprivation are some of the chief causes for truck crashes, but no single factor stands out above all others. This research creates methods for bounding the effect of driving hours of service (HOS) regulations on crash and fatality rates for truck-involved crashes. HOS regulations permit drivers to operate their vehicles and be on duty (i.e., working either as a driver or in some other related activity) for a stipulated amount of time per shift as well as over seven and eight day periods. Because truck drivers spend a majority of their work time behind the wheels of their vehicles, truck safety can be gauged by analyzing HOS regulations. All trucking organizations must comply with HOS rules, and any change in these HOS rules also affects the oper- 1366-5545/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tre.2007.07.007 * Corresponding author. Tel.: +1 213 740 6709. E-mail address: rwhall@usc.edu (R.W. Hall). Available online at www.sciencedirect.com Transportation Research Part E 44 (2008) 298–312 www.elsevier.com/locate/tre