AGRICULTURAL TRANSPORTATION
EFFICIENCY COALITION
and forest products from farms and forests to processing facilities.
Research on Truck Weight Impacts
The Agricultural Transportation Efficiency Coalition reviewed published research on the impacts of trucks and truck weights on public safety and road and bridge condition and here presents key findings, and references to clarifying information, from sources reviewed.
Creating the Interstate System
www.tfhrc.gov/pubrds/summer96/p96su10.htm
Richard Weingroff's 1996 historical survey of the creation and growth of the Interstate System provides context to the debate over truck weight and length limits, acceptable axle configurations and spacings, and the thinking behind the "grandfathered" provisions for individual states. Published by the Federal Highway Administration's Turner-Fairbank Highway Research Center.
Comprehensive Truck Size and Weight Study: Volume II, Chapter 2
"Truck Size and Weight Limits"
http://www.fhwa.dot.gov/reports/tswstudy/Vol2-Chapter2.pdf
This section of the U.S. Department of Transportation's 2000 study (pages 1-10) summarizes the history of federal and state policies on truck weight limits, then (pages 11-24) presents the "current environment," including variances among individual states' weight variances and special permitting policies. Table on pages 13-15 shows weight rules for each state, on state roads and the Interstate, current as of 1994. Published by the Federal Highway Administration.
Comprehensive Truck Size and Weight Study: Volume II, Chapter 5
"Safety and Traffic Operations"
www.fhwa.dot.gov/reports/tswstudy/Vol2-Chapter5.pdf
This section of US-DOT's 2000 study considers truck size and weight policies in all U.S. jurisdictions with respect to public safety, and correlates truck configuration data with statistics on crashes and vehicle stability and control. Graphs on pages 4-8 examine fatalities associated with truck-related crashes; pages 19-20 examine the effects of vehicle design on stability, control, and operation, noting that "braking performance is a general concern that applies to all trucks and is not particularly influenced by changes in truck sizes and weights, if the requisite number of axles and brakes are added as the vehicle's weight increases and all the vehicle's brakes are well-maintained." Published by the Federal Highway Administration.
Large Truck Crash Facts 2006
http://ai.fmcsa.dot.gov/CarrierResearchResults/PDFs/LargeTruckCrashFacts2006.pdf
The 2008 edition of the Federal Motor Carrier Safety Administration's Analysis Division's annual publication contains descriptive statistics about fatalities, injuries, and property damage associated with crashes involving large trucks in 2006. Among the many tables, Table 1 (page 4) shows a continuum of statistics of fatal crashes involving large trucks from 1975 to 2006, with "fatal crashes per 100 million vehicle miles traveled" declining by more than half, from 4.58 in 1975 to 1.94 in 2006.
Comprehensive Truck Size and Weight Study: Volume II, Chapter 6
"Highway Infrastructure"
www.fhwa.dot.gov/reports/tswstudy/Vol2-Chapter6.pdf
This section of the US-DOT's 2000 study considers the relationship between road and bridge design and truck weight and configuration, separating out issues relevant to short-span bridges, long-span bridges, pavement types, and such road features as curvatures and climbing lanes; and correlates speed and axle-spacing as factors in pavement wear. Pages 9-16 discuss the Federal Bridge Formula, with its table of recommended maximum weights for axle groupings at prescribed spacings to protect bridges, adopted in 1975, along with alternative bridge formulas that have been proposed since.
Transportation and Colorado's Agribusiness Industry
http://tinyurl.com/oggcvd
This 2007 report from the Colorado Department of Agriculture points out the constraints the state's relatively low truck size and weight limits place on the movement of basic agricultural products. From page 8: "By altering Colorado's load regulations to conform to those of neighboring states, Colorado can improve the competitiveness of our industry as well as potentially reduce highway congestion by 120,000 truck movements in transporting Colorado's annual harvest." From page 16: "This allowance [loads grossing up to 110,000 pounds via additional length and axle combinations] should be considered for use on all interstate and intrastate roads with the exclusion of crossing designated bridges that would not allow such loads."
Wisconsin Truck Size and Weight Study: Final Report
http://www.topslab.wisc.edu/workgroups/tsws/deliverables/WisDOT_TS&W%20Study_1-1-09_final.pdf
Published in January 2009, this 238-page study notes that (page ES-5) "in recent years, the gap in crash rates between large trucks and all other vehicle types has closed and, in fact, in the State of Wisconsin, large trucks have had a slightly lower fatal crash rate for the past seven years," also pointing out (page ES-6) "commercial vehicles are often involved in long haul traveling with minimal lane shifts or turning movement. In addition, commercial drivers license holders have more training and experience than most drivers." The study notes infrastructure conservation benefits from a 98,000-pound, six-axle configuration (page ES-6 and ES-7): "Taking into account the total bridge costs and the ability to operate on the Interstate, the most successful new configuration, in terms of net benefits, is the six-axle 98,000 semitrailer, which generates the highest savings in transport costs, safety, and congestion. . . . The most pavement-friendly configurations are those with the greatest distribution of weight across axles." In conclusion, the study recommends (page 8-1) the six-axle, 98,000-pound configuration for "highest goods movement, safety, and congestion savings," while noting that the "six-axle 97,000-pound and seven-axle 97,000-pound configurations provide ample goods movement savings and pavement savings." Published by the Wisconsin Department of Transportation.
Minnesota Truck Size and Weight Project: Final Report
http://www.dot.state.mn.us/information/truckstudy/FR2_mndot_trucksizeweight_complete.pdf
This 190-page 2006 study analyzed several possible heavy truck configurations, and "four heavier truck configurations were found feasible and generated net statewide benefits" (page 20), with a matrix of those benefits presented in a table (page 21). Configurations examined did not include the 97,000-pound, six-axle semi-trailer configuration AgTEC recommends, although it is similar to the winter-hauling scenario (99,000-pounds) for the six-axle configuration the study does evaluate favorably. The study finds a slight upward trend in accidents as gross vehicle weight increases but finds net safety benefits accruing, in that (page ES-3) "crash rates per payload ton-mile decrease with a gross vehicle weight increase because fewer truck trips are required to haul a given amount of freight." Published by the Minnesota Department of Transportation.
Truck Activity in Canada: "The Fleet"
http://www.tc.gc.ca/pol/en/Report/TruckActivity/Chapter3.htm
This 6-page report characterizes the size and weight configurations of Canadian trucks, noting (page 2) the "strong influence" the 80,000-pound gross vehicle weight limit on the U.S. Interstate system places on Canadian trucks, "as a large number will cross the border at some point on their trip." The report notes (page 3): "In Canada, the heaviest truck allowed (62,500 kg, or nearly 138,000 lbs.) under an interprovincial agreement requires eight axles." Published by Transport Canada, a Canadian federal agency.
Implications of Future Heavier Trucks for Europe's Bridges
www.colincaprani.com/files/papers/Conferences/TRA08%20-%20OBrien%20et%20al.pdf
This 8-page 2008 study examines the implications for European bridges if an existing trend toward introducing (page 1) "longer and heavier trucks, with up to 8 axles and gross weights of up to 60 tons" continues, in terms of lifetime load effects. "This paper has demonstrated" (page 7) "the importance of cranes and low-loaders as the dominant feature in extreme traffic loading on bridges at a very heavily trafficked site in the Netherlands. Medium wheelbase non-permit trucks do not appear to make a great contribution. . . . It is the opinion of the authors that a significant increase in the allowable number of axles in non-permit trucks will not significantly change the characteristic traffic loading on short to medium span bridges." Published by the Dublin Institute of Technology, School of Civil and Building Services Engineering.
Should the Maximum Length and Weight of Trucks Be Increased? A Review of European Research
www.sml.hw.ac.uk/logistics/downloads/lhvstudy/McKinnon%20-%20LHV%20paper%20-%20final%20-%20ISL%20conference%202008.pdf
This 8-page 2008 study examines technical issues surrounding proposals within various European Union countries to increase size and weight allowances, using the (60-metric-ton gross vehicle weight) Swedish and Finnish experience as a baseline. It points out (page 5) "On the basis of Swedish and Finnish data, TFK (2002) estimated that the use of Longer and Heavier Vehicles cut vehicle trip numbers by 32% and road transport costs by 23%," and that these countries' use of LHVs did not appear prejudicial to movement of freight by rail, since "in Sweden where LHVs have been operating for many years, rail's share of total road and rail tonne-kms in 2005 was roughly twice the EU25 average." Published by the Logistics Research Centre, Heriot-Watt University, Edinburgh, UK.
