Chapter 1
Introduction

Federal regulations that apply on major U.S. highways govern the weight and width of vehicles and the number of trailers that a power unit may tow. These regulations have important economic consequences because trucking accounts for four-fifths of expenditures on freight transportation in the United States, and trucking costs are influenced by truck size and weight. Size and weight limits also influence highway construction and maintenance costs and highway accident losses. The regulations affect international commerce as well because U.S. limits differ from those of Canada and Mexico and because containers shipped in international trade often are not consistent with U.S. regulations.

The most recent extensive revisions in federal truck size and weight limits were enacted in 1983. Since then there have been changes in the use and characteristics of the highway system, as well as important structural changes in the freight industries. Congress has received proposals for revisions to the federal limits from industry groups, state governments, and others. Proposals for changes in federal regulations governing vehicle size and weight have always been controversial, however, because allowing larger trucks could increase some categories of highway costs and attract freight from railroads to the highways. Trucking firms and shippers’ groups typically advocate liberalization of the limits because larger trucks reduce their costs. The railroad industry, highway safety advocacy groups, some trucking firms (especially smaller ones), and some states oppose increases in federal size and weight limits.

In June 1998, Congress enacted the Transportation Equity Act for the 21st Century (TEA-21, Public Law 105-178), which provided $220 billion in highway and transit funding over 6 years. Section 1213i of the act instructs the Secretary of Transportation to request that the Transportation Research Board (TRB) “conduct a study regarding the regulation of weights, lengths, and widths of commercial motor vehicles . . . and develop recommendations regarding any revisions to law and regulations that the Board determines appropriate.” The act



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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Chapter 1 Introduction Federal regulations that apply on major U.S. highways govern the weight and width of vehicles and the number of trailers that a power unit may tow. These regulations have important economic consequences because trucking accounts for four-fifths of expenditures on freight transportation in the United States, and trucking costs are influenced by truck size and weight. Size and weight limits also influence highway construction and maintenance costs and highway accident losses. The regulations affect international commerce as well because U.S. limits differ from those of Canada and Mexico and because containers shipped in international trade often are not consistent with U.S. regulations. The most recent extensive revisions in federal truck size and weight limits were enacted in 1983. Since then there have been changes in the use and characteristics of the highway system, as well as important structural changes in the freight industries. Congress has received proposals for revisions to the federal limits from industry groups, state governments, and others. Proposals for changes in federal regulations governing vehicle size and weight have always been controversial, however, because allowing larger trucks could increase some categories of highway costs and attract freight from railroads to the highways. Trucking firms and shippers’ groups typically advocate liberalization of the limits because larger trucks reduce their costs. The railroad industry, highway safety advocacy groups, some trucking firms (especially smaller ones), and some states oppose increases in federal size and weight limits. In June 1998, Congress enacted the Transportation Equity Act for the 21st Century (TEA-21, Public Law 105-178), which provided $220 billion in highway and transit funding over 6 years. Section 1213i of the act instructs the Secretary of Transportation to request that the Transportation Research Board (TRB) “conduct a study regarding the regulation of weights, lengths, and widths of commercial motor vehicles . . . and develop recommendations regarding any revisions to law and regulations that the Board determines appropriate.” The act

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 stipulates that the study consider regulation of commercial motor vehicles operating on federal-aid highways and that it encompass a review of laws, regulations, other studies, and practices; solicitation of input from the U.S. Department of Transportation (DOT), the states, the motor carrier industry, freight shippers, highway safety groups, air quality and natural resource management groups, and commercial motor vehicle driver representatives; and evaluation of the impact of study recommendations on the economy, the environment, safety, and service to communities. Recommendations are to be addressed to Congress and the Secretary of Transportation. Appendix A contains the text of the section of the act calling for the study. At the request of DOT, TRB formed the Committee for the Study of the Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles to conduct the study called for by Congress. This report is the committee’s response to the legislation’s study charge. The first section of this introductory chapter describes the purposes of truck size and weight regulations. The second section identifies the forces that have driven the evolution of these regulations in the past and that are generating calls for change today. The next three sections identify the principal directions for change that have been proposed, outline the challenges confronting reform, and describe the criteria and methods used by the committee in evaluating possible changes. FUNCTION OF SIZE AND WEIGHT REGULATION The first step in determining whether changes in the federal commercial motor vehicle weight, length, and width regulations would be appropriate is to define the function of the regulations. Several definitions may be given: the function the regulations are perceived to serve today, the objectives of legislators when the regulations were first enacted, a declaration of what the goals of regulation ought to be, or the actual function of the regulations as determined by the consequences of changing them. It is necessary also to distinguish the function of federal regulations from that of size and weight regulations imposed by state and local government. Regulations Today Motor vehicle size and weight regulations are among the most important factors determining road and bridge design and maintenance requirements and the cost of truck freight transportation. All the states regulate the weight and dimensions of vehicles on public roads. In general, these state regulations govern the following dimensions:

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 The maximum weight on any single axle; The maximum weight on any group of axles on a vehicle (for example, the last four axles of a five-axle tractor-semitrailer) as a function of the span of the axle group and the number of axles (this limit is called a bridge formula and is intended to protect bridges from excessive flexural effects by avoiding heavy, clustered, concentrated axle loads); The maximum weight of the entire vehicle; The maximum length, width, and height; and The maximum number of trailers. Some states regulate other dimensions as well, and some impose separate limits for different classes of roads. In all states, various kinds of special permits, exemptions, and grandfather rights allow some trucks to operate at dimensions exceeding the normal limits. There are also special provisions imposing more restrictive limits on certain roads and bridges. Vehicle dimensions control the applicability of other laws as well; for example, certain federal vehicle safety regulations apply to trucks over 10,000 lb, and user fees vary with weight. The states began to regulate vehicle dimensions before World War I. Federal limits were first enacted in 1956 in the legislation that created the federal-aid highway program and were revised in 1975 and 1983. Federal law dictates the axle weight limit, gross weight limit, and bridge formula on the 46,000-mi Interstate highway system, as well as on a network of major roads that includes the Interstates and about 160,000 mi of other roads; dictates minimum trailer length and width limits that the states must permit; and requires the states to allow double trailers. The states enforce limits through roadside inspections at permanent and portable scales. Estimates of the frequency of illegal overloads range from a few percent to 20 percent of all combination trucks on the road at any given time (TRB 1990a, 141), but definitive data on the violation rate do not exist. The content of the regulations and the criteria applied by public agencies to evaluate proposed changes imply that the purpose of the size and weight limits in effect today is to control certain public costs associated with large trucks: Highway construction and reconstruction costs—The strength of pavement and bridges, lane widths, and horizontal and vertical alignment are dictated by the requirements of the largest vehicles on the road.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Highway maintenance and rehabilitation costs—The wear on pavements, shoulders, and bridges depends on vehicle configurations and weights and traffic volumes. Congestion—Larger vehicles generally have less maneuverability and less acceleration capability, require longer distances to pass, and consume more road space. Accidents—A collision involving a large truck and an automobile is more severe on average than one involving only automobiles. Dimensions and configuration affect vehicle handling, stability, and traffic interactions and are believed to affect accident rates. The cost control goal has been apparent in federal as well as state actions on size and weight. The history of the regulations also indicates that the limits have been seen as a mechanism for controlling competition between trucks and other freight modes, although this end is not always made explicit. Federal regulations specify the following vehicle dimensions: The maximum weight on any single axle (20,000 lb) and on any tandem axle, that is, any pair of closely spaced axles (34,000 lb), for vehicles on Interstate highways. The maximum weight on any group of axles on a vehicle (for example, the last four axles of a five-axle tractor-semitrailer), as a function of the span of the axle group and the number of axles, on Interstate highways (the bridge formula). The maximum weight of the entire vehicle (80,000 lb) on Interstate highways—States cannot impose lower weight limits than the federal limits on Interstate highways. The width of vehicles—Federal law requires states to allow vehicles 102 in. wide on the National Network for Large Trucks, a federally designated network that includes the Interstates and 160,000 mi of other roads. Trailer length and numbers—Federal law requires the states to allow single trailers at least 48 ft long and tractors pulling two 28-ft trailers on the National Network. The other main provisions of the federal regulations are as follows: Grandfather exemptions—States in which vehicles exceeding a federal limit were in operation before the enactment of the federal limit may continue to allow the vehicles to operate indefinitely. The exemption applies to state permit operations as well as to general state limits.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Statutory special exceptions—Federal law contains several exemptions applying to particular operations in specified states. LCV freeze—No state that did not allow operation of longer combination vehicles (LCVs, defined in general as multitrailer combinations having any trailer longer than 28 ft, having more than two trailers, or weighing more than 80,000 lb) on roads of the National Network before June 1991 may legalize operation of such vehicles on the National Network. Intrastate public transit buses—These vehicles are temporarily exempt from the axle weight limits. Enforcement—The states are required to certify that they have effective programs for enforcing weight limits on federal-aid roads as a condition for receiving federal highway aid. Appendix B contains the text of the federal size and weight laws. Federal statutory limits do not by themselves dictate vehicle dimensions. State regulations apply on roads where federal limits do not, and grandfather and permit operations of vehicles exceeding statutory limits are common. Many large trucks normally operate with dimensions below the limits (e.g., carriers specializing in commodities of low average density operate below the gross weight limit). Historical Goals of Federal Regulation Federal regulation implies that there are national goals that could not be attained by state regulation alone. The original intent of federal limits is explained in part in the report of the House Committee on Public Works on the bill that became the Federal Aid Highway Act of 1956 (H. Rept. 2022, 84th Cong., quoted in BPR 1964, 10): The committee recognizes that maximum weight limitations for vehicles using the highways are fundamentally a problem of State regulation, but feels that if the Federal Government is to pay 90 percent of the cost of Interstate System improvements it is entitled to protection of the investment against damage caused by heavy loads on the highway. The committee considers that such protection can best be provided by a limitation on maximum axle loadings. The 1956 act initiated the construction of the Interstate highway system, for which the federal share of costs was to be 90 percent. The limits enacted in 1956 were taken from the recommended practices of the American Association of State Highway Officials then in effect.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 The act required the Secretary of Commerce and the states to develop uniform geometric and construction standards for the Interstates. The weight limits would facilitate uniform standards for strength of pavements and bridges, while the width limit apparently was to facilitate uniformity of highway geometric design (BPR 1964, 9–11). The circumscribed role for federal regulation apparently intended in 1956—to protect the federal investment in roads and bridges and allow uniformity of highway geometric design—was broadened in the 1983 revisions to the federal limits. Those revisions included the first requirements that states with more restrictive limits liberalize them to conform with the federal standards. Such minimum standards are not necessary for uniformity of highway design or control of maintenance costs. Their justification is that removing unjustifiably restrictive state limits reduces trucking costs. Evidently, Congress had added the federal regulatory goal of attaining a degree of uniformity in trucking regulations for the sake of the economic benefits of greater truck capacity in interstate commerce (TRB 1986, 28–29, 51–53). The 1991 LCV freeze was the first federal law that prohibited states from allowing vehicles with larger-than-specified dimensions on roads other than Interstates. Such a rule might be imposed on grounds of infrastructure economy, as were the 1956 limits. The LCV freeze was, however, apparently the first federal rule justified in large part as a safety measure. Appropriate Goals The historical record does not supply a full definition of the intended function of motor vehicle size and weight regulations. It would not be inconsistent with the history of their development, however, to define their function as providing a mechanism to balance the potential public costs of truck travel—wear on public infrastructure, accident risk, and congestion—against the benefits of lower shipper and carrier costs for freight transportation. In principle, it should be possible to specify optimum regulations that strike the best balance and allow the public to derive the greatest benefit from the highway transportation system. A comparison with railroads may be instructive in defining the goals of highway size and weight regulations. A railroad company has need of dimensional standards for locomotives and cars so it can design and maintain its rights-of-way, track beds, and equipment consistently. In contrast with a public highway agency, the railroad knows and bears all the costs of changes in the standards and has information on customers’ willingness to pay for new or improved services that would re-

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 quire such changes. Therefore, the railroad’s selection of its dimensional standards is a routine business decision, involving use of marketing and cost data to select standards that will be most profitable. The public highway agency’s problem in selecting size and weight limits is more difficult than the railroad’s for two reasons. First, the taxes and fees paid by highway users are not closely related to the costs users cause, so the agency has much less information than does the railroad about the market and costs. Second, the highway agency is concerned not only with deriving the greatest possible economic benefit from the public’s investment in roads (analogous to the railroad’s criterion of profit maximization), but also with other social values, and is accountable to multiple constituencies with sometimes conflicting interests. Federal determination of size and weight standards as opposed to state regulation has been justified by two arguments, both of which are reflected in the history of the development of the federal standards summarized above. The first argument is that harmonization of standards reduces freight costs and that this benefit can be attained only through coordinated action. For example, nationwide standards may lower costs by reducing the need for vehicle design variations and allowing the same vehicles to operate nationwide. The federal government’s responsibility for interstate commerce justifies federal regulation in such a circumstance. A minimum federal responsibility is to ensure that interstate or international commerce is not severely impeded by unduly restrictive regulations in a single state or small number of states. This argument is prominent in the Interstate Commerce Commission’s (ICC) analysis of the justification for federal intervention in size and weight regulation in its 1941 report to Congress (ICC 1941, 24–26). This first congressionally mandated study of the issue had been ordered by Congress in 1935. At the time, there was no major federal-aid highway program, so the direct federal interest in controlling highway construction and maintenance costs that was later cited by Congress to justify the 1956 federal size and weight limits did not exist. Nonetheless, the analysis remains relevant today. The ICC concluded first, regarding the powers of Congress and the possible rationales for action: that Congress has plenary power to remove unreasonable obstructions to interstate commerce. If State regulations governing sizes and weights of motor vehicles operate in fact to burden or obstruct interstate commerce unreasonably, Congress may enact legislation designed to secure uniformity or in other respects to protect the national interest in the commerce....

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 It is also concluded that under a broad policy seeking to preserve essential forms of transportation, such as those by railroad and by water, as well as by motor truck, or to promote safety in highway use, Congress could establish size and weight limits for motor vehicles, applicable to interstate traffic, lower than those now applicable to such traffic under State laws. Regarding the actual need for federal action, the ICC concluded: with respect to the public highways which serve as the principal arteries of interstate commerce, State limitations may be, and to a considerable extent probably are, less liberal than is necessary for the proper protection of the highways and their appurtenances and of the public safety…. where such conditions exist, the limitations operate as an obstacle to the flow of interstate traffic, render motor transportation more costly, and result in an impairment of service to the public…. in the light of the broad public interest in the securing of as economical and efficient a motor transport service as possible, as well as in the light of the requirements of the national defense, … there is need for Federal regulation of the sizes and weight of motor vehicles…. Burdens on interstate commerce cannot be relieved through the judicial processes; only legislation can afford the needed relief…. considerations of safety and convenience do not, in and of themselves, require that Congress enter this field of regulation, but we do find that the evidence available justifies the conclusion, that if Federal regulation be undertaken for other reasons, there will be need for consideration of certain phases of sizes and weight in their relation to the safety and convenience of users of the highways…. national uniformity of standards is impracticable … on the contrary, Congress should enter this field only to the extent that proves necessary under the circumstances of particular situations….

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 The second argument for federal regulation is essentially the same as the rationale for the federal-aid highway program: that the value of investments in the system of main highways from the point of view of the nation as a whole is greater than the value as seen by the individual states that would otherwise be responsible for investment decisions. For example, a sparsely populated western state whose roads carry a large volume of through traffic between the major population centers of the West Coast and the Midwest might see little need to invest in high-quality through roads to serve its own population and (as long as road use was free) would have no mechanism for capturing any of the economic benefit of the through traffic. The need for federal size and weight regulation is incidental to the need for the federal-aid program: if a local government lacks interest in constructing a road on its own, it is also likely to lack interest in managing or maintaining the road, so federal standards will be needed. Some of the considerations that have played a part in setting size and weight restrictions in the past are questionable as goals for these regulations. Both the TRB Truck Weight Limits study (TRB 1990a) and the recent DOT Comprehensive Truck Size and Weight Study (DOT 2000) indicate that imposing nationwide uniform limits more restrictive than those previously in effect in many states would increase shipper costs by an amount greater than any compensating savings in highway operating costs. Uniformity per se is likely to be less efficient than toleration of regional variability in standards if the variability reflects actual differences in traffic and highway conditions and therefore in the costs of operating trucks of various dimensions. A second questionable goal is attempting to regulate competition among the freight modes by restricting truck dimensions. DRIVING FORCES FOR CHANGE Changes in motor vehicle size and weight regulations have historically been driven by external forces. The limits have changed continually throughout the development of the highway system as a consequence of the expansion of the system, improvements in vehicles and roads, and economic pressures for cost reduction in industry. Improvements in highways and freight vehicles and the resultant changes in size and weight limits, together with innovations in the management of freight and logistics, have been important sources of productivity growth. As long as the external driving forces persist, the regulations will continue to change through the political process. Planning for

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 change affords the public authorities responsible for the highway system an opportunity to manage this process rather than risk haphazard development. The report of a 1990 TRB study committee that considered truck size and weight policy observes (TRB 1990b, 15): In the past, the regulations have been subject to nearly continuous incremental revision. The result has been trucks that are not ideal from the standpoint of highway wear, freight productivity, or safety. Highway engineers are dissatisfied with current standards because heavy truck traffic accounts for a large fraction of road wear. Throughout the country roads and structures do not stand up well to the loads they must carry, and highway agencies lack the funds to perform more frequent maintenance. At the same time, motor carriers and shippers point out that the benefits from reduced freight cost of allowing larger trucks could greatly outweigh the costs of repairing the added road wear that larger trucks would cause; and safety advocates, motorists, and the public are concerned that trucks are involved in a disproportionate share of the most severe highway accidents. Thus, the situation today is that substantial economic benefits could be gained through use of larger trucks, but chronic funding shortages in state highway maintenance programs and fears of the hazards of larger trucks stand in the way of gaining these benefits. In the decade since this report was issued, many conditions have changed: state highway programs have received substantial funding increases; pavement and bridge design methods have advanced, and new technology for enforcing highway regulations and collecting user fees is increasingly available; technology has improved vehicle performance; and the freight and logistics sectors have experienced important technological advances and productivity gains. Federal motor vehicle size and weight limits have not undergone overall revision in this period, so it is likely that the gap between existing limits and optimum vehicle standards is greater than ever. Changes in these three factors—highways, vehicle technology, and freight customer service demands—account for the evolution of size and weight limits throughout the century. The system of paved roads in the United States had reached 500,000 mi by the late 1930s and

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 1 million mi by 1956, and stands at 2.5 million mi today. The construction of a system of roads built to Interstate standards—designed for safe and efficient operation with high traffic volume, high speed, and heavy loads—has been the major highway advance of the latter half of the century. In the United States there was 1,100 mi of divided highway with full access control in 1956, 22,000 mi by 1966, and 42,000 mi by 1976; today there is 57,000 mi (FHWA 1987, Tables SM211, M203; FHWA 2000, Tables HM12, HM 35; TRB 1986, 33–36). Highway agencies also have adopted pavement and bridge designs and pavement and bridge management practices that have reduced the costs of accommodating larger vehicles, and are beginning to apply information technology for traffic management and regulatory enforcement, including systems for automatic screening and electronic identification of trucks to improve enforcement efficiency. Similar technology is used for collecting tolls, and could be applied more widely to levy user fees that would give highway users incentives to consider infrastructure costs and costs to other users in their transportation decisions. Advances in the design of heavy trucks in the past half-century include improvements in diesel engines that resulted in their being used to replace the gasoline engine for nearly all intercity freight by the 1960s, as well as great improvements in brakes, transmissions, and suspensions. These advances have contributed significantly to the productivity of the trucking industry (Gordon 1992) and have made larger loads and long-distance operations feasible. More recently, applications of electronics and information technology have improved operating efficiency and have begun to be applied to improve vehicle control and safety. Trucking industry operating practices are driven by customer demands. Today as in the past, customers place a premium on reliability, speed, and flexibility. Shippers appear to be aware now more than ever of the potential for cost savings through better management of logistics. However, changes in logistics management practices may not have greatly altered shippers’ demands as they affect vehicle size and weight requirements. Shippers have always sought lower freight rates, which can be attained by using vehicles with greater weight and volume capacity. Changes in logistics practices and in the composition of U.S. production and consumption, however, may be altering the relative significance of increasing the volume capacity of trucks as opposed to increasing weight capacity. For example, shipments of high-value manufactured goods (e.g., processed food or electronics) have

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Federal provision for a western LCV network is not a new proposal. DOT evaluated the concept in a 1986 study (FHWA 1986) at the direction of a congressional committee after a 1985 congressionally mandated DOT study of LCVs led to the following conclusion: “There is no compelling reason for designation of a federally mandated LCV network at this time…. There are positive aspects of LCV use, but many unresolved issues argue against their immediate widespread use” (FHWA 1985, S-8). Also in 1999, an American Association of State Highway and Transportation Officials (AASHTO) policy resolution identified various shortcomings in the draft Comprehensive Truck Size and Weight Study and called on DOT to consult with the states and private parties in the course of completing the study (AASHTO 1999). Although DOT had described the purpose of its study as developing a method of analysis rather than policy proposals, the states evidently perceived the additional need for the federal government to address certain of their immediate policy concerns. The state reactions to the DOT study, as well as the history of special state exemptions to federal law, suggest that at least some states have found federal regulatory practices inflexible and unresponsive to local needs. The states might be more satisfied with an approach to the review of federal size and weight regulations that was more open to them and that focused on the practical size and weight issues they confront. Although the history of size and weight regulation shows that demands continually arise to adapt the regulations to changing external circumstances, there is no established mechanism at the federal level for responding to such demands with timely evaluation. The replies of the states to this committee’s request for comments show that they value the function of federal regulation as a buffer protecting state highway programs from the local and short-run economic pressures they face to depart from best management practices. Providing some degree of regulatory flexibility according to an established procedure might help preserve this federal role. International Trade The North American Free Trade Agreement (NAFTA) is an immediate impetus for review of the federal regulations governing truck size and weight. The agreement among Canada, the United States, and Mexico was signed in 1992 and became effective in January 1994. Its provisions reduce barriers to trade among the three countries. The NAFTA parties agreed to seek compatibility of standards related to

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 vehicle weights and dimensions, as well as safety-related vehicle standards and emission standards to facilitate cross-border movement of goods (LTSS 1997, 3). The NAFTA schedule called for agreement on compatibility of size and weight and other vehicle standards by January 1997 as a step toward full cross-border access for trucks by January 2000 (GAO 1996, 19). Limits differ greatly among the three nations. Canada and Mexico allow heavier axle weights than those of the United States. Six-axle tractor-semitrailer combinations are common in both countries, with maximum legal weights of approximately 106,700 lb in Mexico and 95,700 to 116,600 lb (depending on the province and the axle spacings) in Canada. Multitrailer combinations are more important in Canada than in the United States or Mexico (LTSS 1997, 31, 45). However, the heaviest as well as the longest combinations in routine use in North America probably are to be found in certain states in the United States. Recently, an international working group developed a proposal for harmonization measures, under which an International Access Network of roads would be designated by the responsible road authorities within each of the three countries. On this network, trucks meeting specified criteria regarding handling and stability performance and pavement loading would be allowed to operate internationally (LTSS 1999). In principle, a solution would be to require all vehicles in cross-border traffic to comply with the most restrictive nation’s size and weight standards, but presumably the goal of the negotiations is a compromise under which some vehicles closer to Mexican and Canadian standards could enter the United States. A resolution of the issue of harmonization of vehicle standards is not at hand. It should be noted that size and weight regulation is only one obstacle to realization of the objective of free cross-border trucking. Because U.S. weight limits are lower than those enforced in most other countries, cargo containers in international commerce arriving at U.S. ports of entry are commonly loaded to weights that cannot be carried within the 80,000-lb federal limit. A ruling of the Federal Highway Administration (FHWA) allows states to issue permits for containers in international commerce as if they were nondivisible loads (DOT 2000, III-13–III-14). This ruling must be regarded as an arbitrary solution to the problem, considering that some states do require overweight container loads to be broken up and that no such allowance is made for containers in domestic commerce. The history of efforts to reduce conflicts between international commerce and U.S. limits, together with the recent state petitions for federal

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 consideration of local and regional circumstances, illustrates how legitimate grounds for considering changes to the federal regulatory regime frequently arise. Also apparent is the fact that the existing regulatory machinery does not provide orderly procedures for resolving such cases. DIRECTIONS FOR CHANGE Because the environment is dynamic, meeting the goals of federal truck size and weight regulation requires periodic revisions to the regulations, responding to changes in conditions that have affected the use of highways and the costs of highway transportation. Evaluating the adequacy of the regulations and seeking to improve them ought to be a continuous process. A broad range of possibilities for the form of revised federal regulations has been proposed by past studies, private-sector groups, states, and others. The options can be organized into three categories: Policies within the existing framework and precedents of federal truck size and weight regulation. New policies involve changes in axle weight and other dimensional limits, changes in the extent of the road system on which federal standards apply, and provisions such as the 1983 federal law regarding double trailer trucks that requires the states to allow certain configurations on certain roads. Options in this category are consistent with the critical assumptions of the DOT (2000) study that new policies entail no changes in pavement and bridge design practices, basic truck design, or highway user fees. Past size and weight studies such as those of TRB and DOT, have focused mainly on this category of options, and the evaluation methods developed in those studies are most applicable to these options. Approaches outside the existing framework of federal size and weight regulation. These proposals involve changing the structure of the regulations instead of simply changing the limits. There are three important kinds of proposals in this category: Performance standards—regulations that directly specify required vehicle performance instead of attempting to control performance indirectly through dimensional limits. For example, a standard could require that trucks pass a test of resistance to rollover as an alternative to a gross weight limit intended to restrain rollover propensity. Pricing—setting fees that induce truck operators to select equipment with lower public costs. For example, fees related more closely to costs could discourage operation of certain configurations

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 now in use that generate relatively high pavement wear costs (or alternatively, finance the additional maintenance these configurations necessitate). More refined pricing also would affect shippers’ logistical and location decisions. Devolution—returning regulatory responsibilities to the states. These approaches could complement established forms of regulation instead of wholly replacing them. However, existing data and models are inadequate for predicting some of the important conceivable effects of these kinds of policy changes. Options in addition to changing the size and weight regulations that would achieve the same underlying goal of controlling the costs of truck traffic while allowing for efficient freight transportation. Examples of such policies include improved enforcement of size and weight limits and safety regulations; bridge management activities targeted at reducing the effect of trucks on bridge construction, maintenance, and replacement costs and on the risk of bridge failure; changes in pavement design practices; and exclusive truck routes or lanes. Evaluation of such options along with evaluation of size and weight regulatory options could lead to better overall solutions. Box 1-1 lists examples of each of the above three categories. The list includes options for comprehensive overhaul of regulations, as well as changes limited to specific provisions of existing regulations. It includes options that are under active discussion today and others that are receiving little or no attention. Some of the options are described more fully in Chapter 3. CHALLENGES CONFRONTING REFORM As described above, dissatisfaction with various aspects of present federal regulations governing truck size and weight has become widespread. Since the latest revision in 1983, several prominent evaluations of size and weight policy have led to proposals for overhaul of the regulations, supported by objective analysis. Yet these proposals have had little impact on policy because no constituency has formed to support them. Various legislative proposals during the same period have failed to win passage. Any proponent of reform must acknowledge this discouraging record and examine the sources of the difficulties Congress has confronted in dealing with the issue. The historical alignment of opposing forces in debates over size and weight regulation was discussed above. Shippers and carriers,

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Box1-1 Options for Changes in Federal Weight, Length, and Width Regulations and Related Policies Policies within existing framework and precedents of federal truck size and weight regulation These do not entail changes in pavement and bridge design practices, basic truck design, or highway user fees: DOT Comprehensive Study illustrative and policy scenarios (DOT 2000) Uniformity—extension of federal weight limits now applicable on Interstates to all roads on the 200,000-mi federally defined National Network; elimination of grandfather provisions North American trade—heavier vehicles with added axles (six-axle tractor-semitrailer, four-axle truck, eight-axle double 33-ft trailer combination) on the National Network Longer combination vehicles nationwide—long double-and triple-trailer combinations on restricted networks with staging areas; eight-axle double 33-ft trailer combinations on the National Network and access routes H.R. 551—elimination of trailers over 53 ft on Interstates and some other federal-aid roads; freezing of grandfather rights; freezing of state weight limits (including permits) on federal-aid roads Triples nationwide—triple-trailer combinations (seven axles, 132,000 lb) nationwide on a 65,000-mi network of Interstates and other high-quality roads nationwide and state-selected access routes Current proposals, including industry proposals State option for longer combination vehicles Peterson-Cook bill—97,000-lb six-axle tractor-semitrailer state option Case-by-case legislative exemptions from federal standards; e.g., TEA-21 exemptions

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Options for Changes in Federal Weight, Length, and Width Regulations and Related Policies Recommendations of earlier TRB study committees New bridge formula from Truck Weight Limits: Issues and Options (TRB 1990a) Turner proposal (TRB 1990b)—state option to allow nine-axle, 111,000-lb double 33-ft trailer combinations with coordinated bridge management and fee changes Approaches outside the existing framework of federal size and weight regulation Permitting program recommended for heavier trucks on Interstates (TRB 1990a) Performance standards defined as the basis for certification of operator-proposed vehicles Reform of federal user fees to align them closely with costs occasioned, coupled with optimal pavement design; e.g., Road Work (Small, Winston, and Evans 1989) proposal Devolution of regulatory responsibilities to the states Options in addition to changing the size and weight regulations that would achieve the underlying goal of controlling the costs of truck traffic while allowing for efficient freight transportation Improved enforcement of size and weight limits and safety regulations Improved bridge management targeted at reducing the effect of trucks on bridge construction, maintenance, and replacement costs and on the risk of bridge failure Changes in pavement design practices Exclusive truck routes or lanes Note: The above list is not exhaustive, but rather indicates the range of possible changes.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 interested in reducing their costs, have supported liberalization, while parties that expect to be harmed economically by lower trucking costs have opposed it. The latter include railroads; some small trucking companies that do not want to be forced by competition to invest in new equipment; and, in some cases, truck drivers concerned about jobs and working conditions. In addition to these economic interests, other forces have become increasingly important in truck size and weight debates. Motorists’ attitudes toward and perceptions of large trucks have played a central role. Survey data and common experience suggest that automobile travelers find large-truck traffic to be a source of stress and discomfort. In past studies, this effect has been treated as no more than a manifestation of the impacts of trucks on accident risk and congestion. However, there may be additional costs arising from motorists’ antipathy toward sharing the road with large trucks that are independent of the costs of changes in accident frequency and congestion. The test to determine whether these effects are real costs is to see whether they lead to observable changes in behavior that impose costs on travelers. The volume and characteristics of truck traffic on particular roads may affect highway users’ route selections, times of travel, and frequency of trips. Regardless of how important these comfort and convenience impacts may be, however, it is possible that incremental changes to federal size and weight regulations would have little effect on their magnitude. Motorists’ comfort and convenience may be insensitive to incremental changes in some truck dimensions, such as maximum gross weight. Also, although the effect of size and weight limits on the volume of truck traffic is uncertain, it is possible that in some circumstances, making limits more restrictive would increase the volume of truck traffic because each truck could carry less freight. Therefore, motorists would encounter more frequent, smaller trucks per mile of travel, and the net consequences for comfort and convenience would not necessarily be positive. Other important bases for opposition to change in the regulations have included objections on the grounds of the environmental impacts of increased reliance on trucks, as well as concerns, especially among state officials, that any action disturbing the status quo would set in motion a process that would be difficult to control or to maintain in balance. States are wary of any change that could negatively affect highway finance. Already noted above is the problem of the lack of established institutional mechanisms for evaluating proposals from the states, industry, or others for revisions to the regulations. Federal truck size and weight

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 studies, in particular, faced with a highly controversial issue and lacking a clear sense of direction from Congress, have emphasized the poor quality of the information base for supporting objective evaluation of alternative policies. More credible information about the likely impact of changes in size and weight regulations on safety and traffic might not sway some of the strongly held views on the subject, but would facilitate the task of reaching consensus on how to improve the regulations. EVALUATING THE OPTIONS A base of understanding about the likely effects of changes in size and weight regulations has been developed from experience with changes and the results of past evaluations. ICC’s 1941 study cited above was the first analysis of the potential benefits of federal regulation of motor vehicle dimensions. Comprehensive studies of the issue were produced by the Bureau of Public Roads (BPR 1964) and DOT (DOT 1981), and DOT issued two studies of multitrailer combinations (FHWA 1985; FHWA 1986). DOT released the preliminary results of its most recent evaluation of federal limits in 1998 (DOT 1998) and the final report 2 years later (DOT 2000). State highway agencies have conducted numerous analyses of limits during the past 75 years. TRB committees conducted four policy studies on the topic between 1986 and 1990: Twin Trailer Trucks (TRB 1986), Providing Access for Large Trucks (TRB 1989), Truck Weight Limits: Issues and Options (TRB 1990a), and New Trucks for Greater Productivity and Less Road Wear (TRB 1990b). The 2000 DOT study, the TRB studies, and most of the earlier studies employed a common analysis method in which alternative sets of size and weight limits are specified, and predictions are made regarding the truck configurations that would become attractive under the new limits and the volumes of freight these configurations would carry. Engineering and economic models are then used to predict the consequent changes in pavement and bridge construction and maintenance costs, frequency of highway accidents, congestion, freight transportation costs, and pollution. Past studies have tended to reach similar conclusions: that incremental increases in allowable truck size can produce substantial net benefits. Predicted increases in infrastructure costs generally are smaller than predicted freight cost savings, and predicted safety effects are often positive if increasing truck capacity is predicted to reduce total truck-miles of travel. Such conclusions have been controversial. Opponents of larger trucks have argued in particular that the studies have system-

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 atically underestimated the safety and environmental costs of larger trucks and that the highway user tax structure would not allow highway agencies to recoup higher infrastructure costs. ORGANIZATION OF THE REPORT The methods used in past studies to predict the benefits and costs of changing truck size and weight regulations are reviewed in Chapter 2. The review reveals that although much is known about the likely effects of changes in size and weight on the overall performance of the highway system, limitations in the standard evaluation framework have diminished the value of past studies to decision makers. These limitations include, in particular, failure to orient the evaluation toward attaining clearly defined policy objectives and to integrate evaluation with the ongoing process of managing the highway system. Important gaps in understanding of impacts are identified, but it is noted that uncertainty about the outcomes of regulatory change is inevitable; therefore, successful reform will depend on systematic monitoring of the performance of regulation at least as much as on improved prospective evaluations of regulatory proposals. In Chapter 3, a proposal is presented to establish a new federal capability for monitoring truck impacts and evaluating the performance of size and weight regulation, and to open up opportunities for innovation in solving size and weight problems. Three packages of possible changes to federal size and weight limits are also presented. The first is based on the recommendations of the 1990 TRB study, Truck Weight Limits: Issues and Options, which Congress asked the present committee to review. The second is a modified version of that earlier study’s recommendations that addresses criticisms about the practicality of the original proposal, which would represent a redefinition of the federal responsibility for size and weight regulations. The third package, which is presented as an option deserving evaluation, is based on a policy of seeking to maximize highway transport productivity. Finally, a description is given of how truck user fee reforms and the concept of performance standards can reinforce traditional size and weight regulation. A survey of new opportunities for mitigating the adverse impacts of truck traffic and the conflicts between trucks and cars on the highways, including applications of information technology, is presented in Chapter 4. A review of techniques for improving enforcement of truck regulations is included. The committee’s conclusions and recommendations on needed changes in federal size and weight regulations are given in Chapter 5.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 Finally, as the legislative study charge requires, the committee solicited and considered comments on truck size and weight issues from industry, interest groups, government bodies, and others. The comments received are summarized in Appendix C. REFERENCES Abbreviations AASHTO American Association of State Highway and Transportation Officials BLS Bureau of Labor Statistics BPR Bureau of Public Roads DOT U.S. Department of Transportation FHWA Federal Highway Administration GAO General Accounting Office ICC Interstate Commerce Commission LTSS North American Free Trade Agreement Land Transportation Standards Subcommittee TRB Transportation Research Board AASHTO. 1999. Policy Resolution PR-9-99: U.S. DOT Comprehensive Truck Size and Weight Study. Oct. 3. Babcock, C. E. 1998. Bill’s Bounty Isn’t Always in Dollars. The Washington Post, April 6, p. A23. Barnes, D. 1999. Western Governors Request LCV Study. Transport Topics, June 21. BLS. 2001. Multifactor Productivity Trends, 1999. www.bls.gov/news.release/prod3.toc.htm. April 10. BPR. 1964. Maximum Desirable Dimensions and Weights of Vehicles Operating on the Federal-Aid Systems. Doc. 354, 88th Congress, 2nd Session, U.S. Department of Commerce, Aug. DOT. 1981. An Investigation of Truck Size and Weight Limits: Final Report. Aug. DOT. 1998. Comprehensive Truck Size and Weight Study: Draft Volume III Scenario Analysis. Dec. 30. DOT. 2000. Comprehensive Truck Size and Weight Study. Aug. FHWA. 1985. The Feasibility of a Nationwide Network for Longer Combination Vehicles. U.S. Department of Transportation, May. FHWA. 1986. Longer Combination Vehicle Operations in Western States. U.S. Department of Transportation, Oct. FHWA. 1987. Highway Statistics: Summary to 1985. U.S. Department of Transportation. FHWA. 2000. Highway Statistics 1999. U.S. Department of Transportation.

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Regulation of Weights, Lengths, and Widths of Commercial Motor Vechicles: Special Report 267 GAO. 1996. Commercial Trucking: Safety and Infrastructure Issues Under the North American Free Trade Agreement. Feb. Gordon, R. J. 1992. Productivity in the Transportation Sector. In Output Measurement in the Service Sectors (Z. Griliches, ed.), Chicago, Ill., pp. 371–427. ICC. 1941. Federal Regulation of the Sizes and Weight of Motor Vehicles; Letter from the Chairman, Interstate Commerce Commission. 77th Congress, 1st Session, House Document No. 354, Government Printing Office, Aug. 14. LTSS. 1997. Harmonization of Vehicle Weight and Dimension Regulations Within the NAFTA Partnership. Working Group 2—Vehicle Weights and Dimensions, FHWA, U.S. Department of Transportation, Oct. LTSS. 1999. Highway Safety Performance Criteria In Support of Vehicle Weight and Dimension Regulations: Candidate Criteria & Recommended Thresholds. Working Draft for Consultation. Nov. Maine Municipal Association. 2000. 2000 Federal Issues Paper. Small, K. A., C. Winston, and C. Evans. 1989. Road Work: A New Highway Pricing and Investment Policy. Brookings Institution Press, Washington, D.C. TRB. 1986. Special Report 211: Twin Trailer Trucks: Effects on Highways and Highway Safety. National Research Council, Washington, D.C. TRB. 1989. Special Report 223: Providing Access for Large Trucks. National Research Council, Washington, D.C. TRB. 1990a. Special Report 225: Truck Weight Limits: Issues and Options. National Research Council, Washington, D.C. 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. Woolard, R. 2001. Weight-Limits Increase Urged for Maine I-95. Transport Topics, June 25.