The Army classifies its vehicles on the basis of such factors as function and physical characteristics. For example, tracked vehicles (Abrams Tanks and Bradley Fighting Vehicles) are classified as Army combat vehicles; wheeled vehicles (trucks, automobiles, cycles, and buses) are classified as Army motor vehicles. Within the Army motor vehicle grouping, vehicles are further separated into tactical and non-tactical categories and within the tactical grouping, into light, medium, and heavy classifications based primarily on vehicle weight. The M939 series trucks are accounted for as part of the Army motor vehicle’s medium tactical fleet. The Army reviews operational requirements for its vehicle fleet in an effort to improve readiness. From January 1983 through October 1993, the Army upgraded its 5-ton medium tactical fleet by purchasing about 34,900 M939s to replace aging and obsolete trucks. The new truck, designed to operate on and off road, maintained the basic design of its predecessors but came equipped with such first-time standard equipment as air-brakes and automatic transmissions. At present, the Army has three variations and nearly 40 different models of the M939 in its inventory. Depending on the model, the truck performs multiple duties that include hauling cargo, collecting refuse, transporting troops, and operating as a tractor or wrecker. The last M939s were fielded in late 1993. Should vehicles or equipment prove dangerous or unsafe to operate, the Army Safety Center, Transportation School and Center, and Tank-Automotive and Armaments Command (TACOM) are responsible for identifying problems and disseminating information. Among other duties, the commands collect and evaluate information from accident investigations and field reports. They also issue Army-wide safety alerts, precautionary messages, and other information warning of identified dangers with equipment and vehicles. Our two analyses and the analysis conducted by the Army Safety Center all involved comparisons of different types of accident data collected over different time frames. Nevertheless, all of the analyses showed that the M939 had a higher accident rate than each type of comparison vehicle. In our first analysis, we reviewed data from January 1987 through June 1998 and compared selected M939 accident statistics with those of the rest of the Army motor vehicle fleet. We reviewed the accident categories in terms of “fatal accidents,” defined as any accident event in which at least one occupant of an Army motor vehicle died; “occupant deaths,” defined as the total number of Army motor vehicle occupants killed; “rollovers,” defined as any vehicle that did not remain upright as the result of an accident; and “rollover deaths,” defined as those occurring to occupants of Army motor vehicles that rolled over as a result of an accident. In analyzing this selected accident information compiled by the Army Safety Center, we found the frequency of M939 accidents high in each instance. For the 11-1/2 year period reviewed, the M939 series truck inventory averaged 26,991, or about 9 percent of the average annual Army motor vehicle inventory of about 314,000 vehicles, and accounted for about 15 percent of the total Army motor vehicle accidents. Appendix I shows the actual figures by year, 1987-1998. Our comparison of M939 accident statistics with accident statistics for the rest of the Army motor vehicle fleet showed that the M939 accounted for about 34 percent of all Army motor vehicle fatal accident events, and 34 percent of all Army motor vehicle occupant deaths. Comparative rollover statistics revealed much the same. The M939 rollovers accounted for 17 percent of the total Army motor vehicle rollovers, and 44 percent of the total Army motor vehicle rollover fatalities. Figure 2 shows these accident statistics. In our second analysis, we used Department of Transportation published data for years 1987-1996 and compared the accident rate for M939s with the rate for single-unit medium and heavy commercial trucks (which are physically similar to M939s). According to an agency official, the Department of Transportation defines “fatal crashes” as any event in which someone is killed in a crash—vehicle occupant or otherwise—and “truck occupant fatalities” as a fatality of an occupant of a single-unit truck. These comparisons revealed that the accident rates for the M939 were substantially higher than those found for the commercial trucks. However, Army officials point out that commercial trucks are driven almost exclusively on paved roads; the M939 is driven on both paved and unpaved roads. We found that over the 10-year period, 1987-1996, the frequency rates of fatal crashes per million miles driven for M939s averaged about seven times higher than those for commercial trucks. The M939 accident rate ranged from a high of 12 to a low of 3 times higher than the commercial truck rate. In 1988, the M939’s accident rate was 0.23 and the commercial truck rate was 0.02—about 12 times higher; and in 1992, the M939 accident rate was 0.056 and the commercial truck rate was 0.018—about 3 times higher. Figure 3 shows these statistics. We also found that, over this same 10-year period, the M939 occupant fatality rate averaged about 30 times higher than those for commercial trucks. The M939 occupant fatality rate ranged from a high of 59 to a low of 13 times higher than the commercial truck rate. In 1995, the M939 occupant fatality rate was 0.165 and the commercial truck rate was 0.0028—about 59 times higher; and in 1989, the M939 rate was 0.046 and the commercial truck rate was 0.0035—about 13 times higher. Figure 4 shows these statistics. The Army Safety Center’s analysis reviewed accident data from October 1990 through June 1998. In this analysis, the accident rate of the M939 was compared with accident rates for another series of trucks—the M34/M35 series 2-1/2 ton truck. Army officials advised us that this truck was most comparable with the M939. The analysis reviewed accidents categorized as Class A mishaps. Army Regulation 385-40 defines a “Class A” mishap as an accident where total property damage equals $1 million or more; an Army aircraft or missile is destroyed, missing or abandoned; or an injury and/or occupational illness resulting in a fatality or permanent total disability. Because an M939 costs significantly less than $1 million, almost all Class A mishaps involving an M939 are so classified because they result in a death or permanent total disability. The Army Safety Center’s analysis found accident rates for M939s to be higher than the comparison vehicles. The analysis showed M939 Class A mishap frequency rates per million miles driven to be 3 to 21 times higher than those of similar M34/M35 series 2-1/2 ton trucks. For example, the 1995 Class A mishap rate for the M939 was 0.21 and for the 2-1/2 ton M34/35s, it was 0.01 per million miles driven—about a 21-fold difference. Figure 5 shows this comparison. The Army has initiated a program to improve the M939’s safety performance and, according to TACOM estimates, plans to spend around $234 million for various modifications. Most of the modifications are the direct result of corrective actions suggested in studies. These studies focused on identifying root causes of M939 accidents based on information contained in accident investigation reports. On the basis of the studies’ findings, the Army concluded that the overall truck design was sound but that some modifications were necessary to improve the truck’s safety performance. Planned modifications include $120 million for upgrading the trucks tires, altering brake proportioning specifications, and adding anti-lock brake kits. Other modifications include $114 million to install cabs equipped with rollover crush protection systems and improve accelerator linkage. The modifications, for the most part, will be completed by 2005 with the M939s remaining in service during the process. To identify possible mechanical problems or performance limitations contributing to M939 accidents, the Army conducted two studies and a computer simulated modeling analysis. Although M939 trucks have been in service since 1983, Army Safety Center personnel stated that no aberrant accident statistics appeared before early 1992. However, during 1990-91, with the increased operating tempo associated with Desert Shield/Desert Storm, there was an increase in fatal accidents and deaths attributable to M939s. In August 1992, TACOM issued Safety of Use Message 92-20 discussing M939 performance limitations. This message warned of the truck’s sensitive braking system—specifically that, when the truck is lightly loaded and on wet pavement, aggressive braking could cause rear wheel lockup, engine stall-out, power steering inoperability, and uncontrolled skidding. The Army began taking a closer look at the M939’s accident history after circulating Safety of Use Message 92-20. Between 1993 and 1995, TACOM, the Army Safety Center, and the Army Transportation School and Center initiated a review of M939 accident reports and began putting together evidence that validated the need for the studies. Also, in an effort to reduce the number and severity of M939 accidents, the Army issued Ground Precautionary Message 96-04 in December 1995, limiting M939s to maximum speeds of 40 miles per hour on highway and secondary roads and 35 miles per hour over cross-country roads. Between September 1995 and June 1997, TACOM conducted two studies and a computer simulation analysis. The studies among other things, recreated and analyzed repetitive events cited in many accident investigation reports and discussed in Safety of Use Message 92-20. The two studies and modeling analysis focused on tire and air brake performance under various conditions. On the basis of the project’s findings, TACOM concluded the overall truck design was sound and nothing was significantly different between the M939 and its commercial counterparts produced during the same time period.