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I.1 Large Truck Incidents and Accidents This appendix provides information that may be used in the absence of locally specific infor- mation about large truck incidents and accidents. Given their frequency, network proximity to populated areas, and impact on the traveling public, large truck accidents have been an ongoing focus of many studies by government agencies and academicians. Some of the more recent analy- ses are described below. Information from U.S.DOTâs NHTSA General Estimates System indicates that between 2002 and 2006, large truck accidents accounted for between 4.5 and 5.0 percent of reported accidents involving passenger cars, motorcycles, light trucks, large trucks, and buses (20). FMCSAâs Large Truck and Bus Crash Facts 2007 report contains accident information for large truck crash occurrences by time of day, day of week, roadway type, body size and type, and haz- mat cargo (including commodity groups) (21). According to the same report, 3.8 percent of large trucks involved in fatal crashes in 2007 were carrying hazmat cargo, while 3.1 percent of trucks involved in non-fatal crashes were carrying hazardous materials. An FMCSA analysis brief from 2004 reported that, on average, 4.2 percent of large trucks in fatal crashes were carrying hazmat cargo between 1991 and 2000, while 4.4 percent of trucks involved in non-fatal crashes that required a tow-away were carrying hazardous materials, suggesting some improvements (22). These statistics do not appear appreciably different from the proportion of U.S. truck miles trav- eled while requiring a hazmat placard, according to the 2002 Vehicle Inventory Use Survey data (as listed in Appendix H, Table H.1). NHTSAâs Traffic Safety Facts 2007 report lists national accident rates for large trucks. Crash data reports suggest continuing improvement in accident rates from the 1970s through 2007. In 2007, the involvement rate per 100 million vehicle miles traveled was 2.02 fatal crashes, 33 injury crashes, and 147 property-damage-only crashes, for a combined involvement rate of 1.82 large truck crashes per million vehicle miles traveled (23). To put this in perspective, a single 20-mile Interstate segment with approximately 2,000 trucks per day (on an annual average) would be expected to see more than 26 large truck accidents per year given the 2007 accident rates. If approximately 4 percent of large truck accidents involve haz- ardous materials according to FMCSA, and approximately 5 percent of all U.S. truck miles are driven while trucks are required to carry a hazmat placard, this roadway segment could expect to see between one to two placarded large truck accidents per year, assuming that national averages apply. Since trucks that carry hazardous materials below threshold levels are not required to have placards, it is likely that the actual number of large truck accidents involving hazardous materials on this segment would be greater. For heavily industrialized areas with even greater proportions of hazmat traffic, the number of hazmat accidents on this segment would be even larger. I-1 A P P E N D I X I Large Truck Incident and Accident Information
The Large Truck and Bus Crash Facts 2007 Report also lists hazmat commodity groups involved in hazmat accidents for fatal and non-fatal crashes, including whether or not hazardous material was released. Flammable liquids are carried in the highest proportion of hazmat truck crashes, followed by gases, and then explosives, corrosives, and miscellaneous dangerous goods (order depending on whether fatal or non-fatal crashes are considered). A more detailed accident analysis by hazmat commodity group is presented in Battelleâs 2001 Report on Comparative Risks of Hazardous Materials and Non-Hazardous Materials Truck Shipment Accidents/Incidents (24). According to this report Class 3 shipments account for about 64 percent of the en route accidents with releases and about 52 percent of the non-release accidents. Class 3 shipments along with Categories 2.1, 2.2, 5.1, 5.2, 8, and 9, represent about 94 percent of all en route accidents with releases and about 93 percent of all en route non- release accidents (p ES-3). The report also estimated total economic impacts for roadway hazmat accidents including injuries and deaths, cleanup costs, property damage, evacuation, product loss, traffic delay, and environmental damage. According to the report Class 3 represents 56 percent of all of the impacts, while Categories 8, 2.1, 2.2, and 9 represent 13 per- cent, 9 percent, 6 percent, and 7 percent, respectively. These five categories alone account for approxi- mately 91 percent of the estimated annual impacts for HM shipments. No other category accounts for more than 3 percent of the total impacts (p ES-4). Accounting for at least these five categories of hazmat transport is likely to be essential to under- standing incident and accident impacts in most HMCFS studies that evaluate vulnerability and risk. I-2 Guidebook for Conducting Local Hazardous Materials Commodity Flow Studies
