Longer Combination Vehicle Safety Study Grant uri icon



  • Longer Combination Vehicles (LCVs), a sub-class of commercial vehicles, are large trucks with two or more cargo spaces. Due to their high productivity and economic and fuel consumption efficiency, the use of LCVs has been increasing, both in terms of the number of vehicles on the road and in terms of the number of miles they are driven. However, the safety performance of LCVs is not yet fully understood. It has been the subject of much debate on the national and local levels. The relatively small number of LCVs in operation and the small number of crashes involving these vehicles makes it difficult to study the safety impacts of LCVs using data sets and methodologies similar to those applied to commercial motor vehicle safety [such as the Fatality Analysis Reporting System (FARS) and the National Automotive Sampling System/ General Estimates System (NASS/GES)].

    A study conducted by Woodrooffe and Associates and focused on comparing the safety performance of LCVs with other vehicles in Alberta, Canada found LCVs to have the lowest collision exposure rate of all vehicle classes. Adverse conditions, such as weather and road surface, were present in 42 percent of all LCV collisions. The study concluded that Alberta's Infrastructure's permit system (selective routing, restrictions on vehicle speed, restricted time of day operation, enhanced driver qualification and operating restrictions during adverse road and weather conditions) was a vital factor in creating a safe operating environment for LCVs. A study of large trucks by Montana department of transportation in 1995 yielded similar results. The study concluded that there was no indication that there is a higher frequency of large truck accidents than for all vehicles traversing the interstate and the primary system. Crash data for Idaho highways from 1990 through 1998 showed that the crash rates for triple trailers were less than that for single of double trailers. Fatal crash rates were also lower for triple trailers.

    A report on LCVs and fatal crashes nationwide, prepared jointly by the Center for National Truck Statistics in the University of Michigan and the Federal Highway Administration, was inconclusive stating:

    “Based on the data presented, no conclusion can be made on the relative safety of LCVs compared to other truck combination. First, data on mileage driven are based strictly on trailer number and length, while the definition of LCV used in the study is based partly on weight. Second, since LCV travel is rare, it is difficult to calculate the precise number of miles driven. Similarly, LCV fatal crashes are so infrequent that the number varies greatly from year to year. Based on the existing data, LCVs do not appear to be considerably more or less safe than other combination trucks. Amore definitive conclusion could be reached only after further collection of data and additional analysis”

    The purpose of this research project is to undertake an in-depth review of the real-world operation of longer combination vehicles in a sample of western states where they currently operate. The proposed research project will examine the relative crash rates of longer combination vehicles LCVs and non-LCVs and compare the safety performance of LCVs as a class of commercial trucking with non-LCVs. The research will also investigate the contributing factors to LCV-related collisions.

date/time interval

  • January 1, 2004 - January 1, 2005