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41 Truck Size and Weight Rules in Congress, with the support of industry groups and some states, but no major revision in federal legislation has been Policy Description enacted since 1982. Studies conducted in 1990 and 2002 by Laws and regulations governing truck size and weight lim- TRB50a,50b,50c concluded that liberalizing size and weight its have been enacted to serve various purposes. The first state regulations by allowing vehicles with greater cargo volume laws date back to the early 1900s, while the first federal laws capacity and/or greater cargo weight capacity could reduce date from 1956 when the current federal-aid highway pro- fuel consumption in freight transportation and also reduce gram was created. The purpose of earlier laws and regulations total shipper costs. The main arguments against increasing was to fix design parameters for road construction. The 1982 the limits have been that (1) highway safety would be de- Surface Transportation Assistance Act (STAA), which pre- graded; (2) diversion of freight from rail to truck would in- empted state regulations more restrictive than the federal crease social costs; and (3) highway agencies could not af- ford the cost of upgrading infrastructure to accommodate limits on the Interstates, was designed to reduce the costs of larger trucks. The 1990 TRB studies concluded that the interstate commerce. The 1991Intermodal Surface Trans- safety impacts of liberalized limits would be positive be- portation Efficiency Act (ISTEA), which blocked the states cause the dominant influence on safety would be a reduc- from allowing expanded use of longer combination vehicles tion in truck VMT. However, the 2002 TRB study acknowl- (LCVs), was justified by Congress as a safety measure (50a). edged that understanding of the safety factors that The main provisions of the current laws and federal regula- determine the safe performance of large trucks is incom- tions are as follows: plete and therefore called for regulatory changes to be tested in rigorously monitored large-scale pilot tests. Re- Maximum gross weight of vehicles on Interstate highways: garding highway agency costs, the TRB studies recom- 80,000 lbs mended that truck fees be adjusted to cover the cost of pro- Maximum axle weight on Interstate highways: 20,000 lbs viding infrastructure for them. The studies predict that on a single axle; 34,000 lbs on a tandem axle liberalizing limits would divert some freight from rail to States may not impose lower limits than the federal limits truck. This diversion would not increase the social cost of on Interstate highways freight transportation, provided (1) trucks paid fees that Width of vehicles: states must allow 102 in. on the National covered their infrastructure costs; and (2) pollution, safety, Network (Interstates plus 160,000 miles of other main roads) and congestion effects are small or positive. Trailer length and numbers: states must allow single trail- The 2002 TRB study emphasized that changes in size and ers at least 48 feet in length and tractors pulling two 28-ft weight regulations made in coordination with complemen- trailers on the National Network. tary changes in highway management would offer the greatest potential for improving system performance. The Grandfather clauses in federal law allow the operation of study recommended (1) adjustments to truck fees to cover trucks not complying with federal limits in states where such highway agency costs; (2) improved bridge management; trucks were in operation at the time of the enactment of the (3) systematic monitoring of truck traffic; (4) reform of en- federal limit. The states regulate size and weight on state roads forcement methods; and (5) vehicle safety regulations gov- not covered by federal law. erning the performance of larger trucks. The most important category of truck exceeding the fed- The most recent study by the USDOT did not attempt to eral limits that operates in the United States is the LCV, a ve- resolve the issue of whether productivity gains from in- hicle with two trailers having a combined total length greater creased limits would outweigh safety costs. The report noted than that of the two 28-ft trailers allowed by federal law or that LCVs ". . . generally show poorer stability or control with three trailers. Most LCV operations are subject to max- properties than the base tractor-semitrailer configuration." imum gross weight limits of greater than 80,000 lbs. LCVs op- The study also reported productivity gains but left the ques- erate on the turnpikes of several eastern states and more ex- tion of net benefits or costs open.51 tensively in a group of western states (Figure 4-3). Separate from the Federal limits, the variation in size and weight rules among western states produces economic ineffi- Policy Impacts ciency. First, the variation reduces competition because the The benefits and costs of increasing the federal size and 50b TRB. 1990a. Special Report 225: Truck Weight Limits: Issues and Options. National weight limits have been debated for decades. Bills that Research Council, Washington, D.C. would liberalize the limits have been introduced repeatedly 50c TRB. 1990b. Special Report 227: New Trucks for Greater Productivity and Less Road Wear: An Evaluation of the Turner Proposal. National Research Council, Washington, D.C. 50aTRB. 2002. Special Report 267: Regulations of Weights, Lengths, and Widths of 51 USDOT, Comprehensive Truck Size and Weight Study: Executive Summary, Commercial Motor Vehicles. National Research Council, Washington, D.C. August 2000, p. ES-10.

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42 Source: U.S. Department of Energy, Fact #411: February 13, 2006 States that Allow Longer Combination Vehicles Note: Michigan allows double-trailer combinations exceeding 80,000 lbs, but with restrictions that prevent the operation of the LCVs illustrated. Figure 4-3. States that allow longer combination vehicles. equipment acceptable in one state cannot always be used in "Federal uniformity scenario" in which the grandfather pro- neighboring states. One option for carriers wishing to do visions in Federal law would be revoked and states would be business in multiple western states is to use equipment that required to adopt the Federal weight limit of 80,000 pounds. complies with the most stringent state rule under which they In a subsequent study, USDOT analyzed a "western unifor- operate, but this would put them at a competitive disadvan- mity scenario" in which the maximum GVW limits of 13 tage with other carriers that can run longer and heavier western states would be harmonized at 129,000 pounds. (This trucks. Another option for carriers is to purchase extra equip- limit is near the high end of the range among the grandfa- ment for use in particular western states, but this will also thered states.) Table 4-4 summarizes the impacts of these two raise costs for the carrier compared with rivals that operate scenarios; see Appendix B-2 for more information on these within only one state. Finally, carriers could have drivers stop impacts. at state lines to readjust loads to comply with rules in the next state, but this process will also increase costs and make oper- ations more complicated. Unexpected Impacts Harmonizing the size and weight rules among the grand- fathered western states would improve the economic effi- Regarding the Federal rules, this is a case in which both ciency of the freight transportation system, but such a change Congress and the USDOT are well aware of the impacts of the would also have other effects on the freight system, depend- decision not to raise the limits beyond their present levels. In ing on the levels at which the harmonized standards are set. 1982 and 1991 Congress made clear decisions to come down Two USDOT studies shed some light on how the impacts on the safety side of the issue. It did so in full knowledge of on the freight system would differ depending on where the the productivity cost, and the USDOT has made no effort to harmonized standards are set. One included modeling of a persuade Congress to do otherwise.