Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles: Special Report 267 (2002)

Federal and state regulations govern the weight and dimensions of trucks, buses, and trailers on U.S. highways. The 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 the convenience and safety of highway travel. The regulations affect international commerce as well because the 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 1998 Transportation Equity Act for the 21st Century directed 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 operating on Federal-aid highways to which Federal regulations apply … and develop recommendations regarding any revisions to law and regulations that the Board determines appropriate.” TRB formed the Committee for the Study of the Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles to conduct this study. The committee’s conclusions, presented below, address the performance of federal size and weight regulations and the adequacy of information available for guiding regulatory decisions. These conclusions are based on a review of past evaluations conducted by the U.S. Department of Transportation (DOT), TRB, and others. The committee’s recommendations involve both organizational arrangements designed to promote reform of the federal regulations and regulatory and management changes intended to improve the efficiency of freight transportation and reduce the public costs of truck traffic.

Throughout its work, the committee found that a lack of information about the costs and benefits of truck transportation and the impacts of the size and weight regulations hindered its effort to provide useful policy advice. Every past body that has examined these issues has encountered the same difficulty. Regulatory decisions on such complex matters will unavoidably entail some risk. Nevertheless, the com-

mittee believes the degree of uncertainty surrounding the question of size and weight regulation is unnecessary. This uncertainty could be alleviated if procedures were established for carrying out a program of basic research and for conducting evaluation and monitoring as a permanent component of the administration of the regulations. The committee’s recommendations include a proposal for such arrangements, which would allow the federal and state governments finally to enact fact-based truck size and weight regulations.

1. Opportunities exist for improving the efficiency of the highway system through reform of federal truck size and weight regulations. Such reform may entail allowing larger trucks to operate.

Present federal standards are for the most part the outcome of a series of historical accidents instead of a clear definition of objectives and analysis of alternatives. The regulations are poorly suited to the demands of international commerce; their effectiveness is being eroded by ever-expanding numbers and types of special exemptions, generally granted without evaluation of consequences; and freight traffic is bypassing Interstate highways, the safest and most efficient roads, to use secondary roads where limits are less restrictive, but the costs generated by that traffic are higher. The greatest deficiency of the present environment may be that it discourages private- and public-sector innovation aimed at improving highway efficiency and reducing the costs of truck traffic because vehicle regulations are infleexible and because highway users are not accountable for all the costs they generate.

2. Appropriate objectives for federal truck size and weight regulations are to facilitate safe and efficient freight transportation and interstate commerce, to establish highway design parameters, and to manage consumption of public infrastructure assets.

The legislative history indicates that these three objectives are consistent with the intentions of Congress in enacting the regulations. These objectives are worthwhile, and truck size and weight regulation by the federal government contributes to their attainment, although the regulations ought to be complemented by other policies aimed at achieving the same goals. Evaluation of federal size and weight regulation should take into account how it affects all costs of highway transportation.

3. Changes in truck size and weight regulations made in coordination with complementary changes in the management of the highway system offer the greatest potential to improve the functioning of the system.

The best way to control the costs of accommodating existing and future truck traffic is by coordinating practices in all areas of highway management: design and maintenance of pavement and bridges; highway user regulations, including vehicle and driver regulations related to safety; and highway user fees. Imposition of cost-based user fees is a regulatory approach that could usefully supplement or partially replace size and weight regulation to produce more efficient control of the public and private costs of truck transportation. Whenever Congress contemplates changing policy in any one of these three areas in the federal-aid highway program, it should at the same time consider the need for complementary changes in the other two.

4. The methods used in past studies have not produced satisfactory estimates of the effect of changes in truck weights on bridge costs.

Past studies have not evaluated the changes in the risk of bridge failure or in useful life that would be caused by changes in truck weights. Instead, they have estimated the cost of maintaining the existing relationship of legal loads to bridge design capacity through bridge replacement. The estimated cost of these bridge replacements is the biggest component of the projected costs of accommodating larger trucks; however, many of the projected replacements would, if actually carried out, buy very little risk reduction. Past studies have not included quantitative evaluation of alternative methods of attaining the same or greater risk reduction through much less costly bridge management strategies.

5. It is not possible to predict the outcomes of regulatory changes with high confidence.

Development of improved models for analyzing the costs of operating trucks of different designs would be worthwhile. However, models and data will never be adequate for providing more than plausible indications of how institutions, markets, and technology will react to regulatory changes, especially in the long run. This inevitable uncertainty is not an argument for inaction, since maintaining the status quo would guarantee the loss of important opportunities for reducing the costs of

transportation. Responsible regulation is a process: the regulatory authority should do the best prior analysis possible, but once regulations have been changed, the consequences must be systematically observed and adjustments made where necessary. The chances that a regulatory change will yield a positive outcome will be enhanced if highway users have been given incentives to act in consonance with the public interest through enforcement, user fees, and application of performance standards in regulation.

6. It is essential to examine the safety consequences of size and weight regulation. Research and monitoring needed to understand the relationship of truck characteristics and truck regulations to safety and other highway costs are not being conducted today.

Understanding of these relationships is needed to design improved highways, vehicles, and safety management and pollution control programs, and to provide a solid basis for truck size and weight regulation. Progress toward reducing uncertainties surrounding the most critical interactions has been nearly nonexistent during the past decade. At least as important as the ability to predict the impacts of changes is to have information systems in place that allow observation of the performance of regulations and the consequences of changes once they have been made.

Promising techniques are available for improving the safety of large trucks. These techniques include vehicle designs for better control and stability, information technology applications for control and stability and collision avoidance, technology applications designed to improve enforcement, improvements in operator certification and training, and changes in highway design. However, little is known about the effectiveness of the majority of such measures that have been proposed. Because of this knowledge gap, as well as a lack of scientific understanding about the relation of safety to truck design, road features, and other factors influencing risk, it is likely that important opportunities to reduce accidents are being missed, while resources are being wasted on ineffective actions.

7. Although violations of size and weight regulations may be an expensive problem, monitoring of compliance with the regulations is too unsystematic to allow the costs involved to be estimated.

There is a need for direct and systematic observation of the frequency and impacts of oversize and overweight vehicles so that the costs

of violations (as well as of legally operated overweight permit vehicles) can be known and the effectiveness of enforcement methods evaluated. The technology needed for low-cost monitoring is now available.

Congress should create an independent public organization with a charter to observe and evaluate commercial motor vehicle performance and the effects of size and weight regulation. This organization, referred to here as the Commercial Traffic Effects Institute, would be chartered to develop federal size and weight standards and related highway management practices, recommend regulatory changes, evaluate the results of the implementation of new regulations, and support state implementation of federal regulations. The Institute would be authorized to enter into agreements with private-sector entities to conduct joint programs of data collection, research, and evaluation.

Three considerations demonstrate the need for a new organizational arrangement. First, under present practices, federal size and weight policy has been deadlocked for more than a decade, in spite of general dissatisfaction with the regulations. Second, under the present system, regulatory changes that have occurred have been enacted without benefit of objective analysis or full public comment. For example, no new federal size and weight regulation has ever been subjected to a conclusive follow-up evaluation, and virtually no new information has been produced in the past decade that would help resolve the question of the safety effects of regulatory changes. Third, the committee’s recommendation for a new system for federal supervision of state permitting (Recommendation 3 below) calls for federal oversight functions that are not consistent with the responsibilities and competencies of any existing federal agency.

Legislation creating the Institute should define the organization’s objective as reducing the public and private costs of truck freight and passenger coach transportation by developing proposals for changes in size and weight regulations, as well as changes in related highway system management and operating practices, including user fee policy. The Institute should be charged with promoting innovation by providing a means to evaluate and implement private-sector or state

proposals for new motor vehicle or highway operating practices that would require federal regulatory accommodation.

The legislation that creates the Institute should define the scope of its activities by specifying three distinct functions:

• The conduct of pilot studies of proposed new vehicles and related operating practices, as well as research on the relationship of vehicle characteristics to highway transport costs. The Institute would solicit proposals for pilot studies and research from the private sector and the states, and would conduct studies jointly with them.

• Monitoring and program evaluation on an ongoing basis. Program evaluations would be conducted to measure whether practices intended to control accident risks and to operate highways efficiently (including size and weight regulations) were functioning as intended. Monitoring would consist of systematic observation in three areas: truck and coach traffic volumes and the distributions of vehicle dimensions and configurations; the administration of regulations, including enforcement and fees; and costs of truck traffic to highway agencies and to the public.

• Support for state implementation of federal size and weight regulations. The Institute should be responsible for reviewing state permitting practices and for developing model regulations and permitting practices as guidance for the states, as described in Recommendation 3 below.

The Institute should be required to recommend to Congress and the Secretary of Transportation changes in federal regulations when there is evidence that such changes would further the congressionally defined objective of reducing the public costs of commercial highway transport. The Institute should be authorized to make recommendations for harmonizing areas of federal highway policy related to size and weight regulation and to truck costs, including safety regulation, enforcement, infrastructure design and management, and user fees. It would not be inconsistent with the functioning of other areas of federal regulation to empower an executive agency to change federal size and weight limits, within boundaries specified by Congress, in response to needs revealed by monitoring and evaluation.

The Institute should be governed by a board with members drawn from the federal and state governments and the private sector. Funding for

core and continuing activities should be from federal highway user fees. Private sponsors of proposed new vehicles or regulations should participate in funding the evaluations of their proposals. A professional staff with diverse expertise would be essential.

The board should be required, as its first responsibility, to prepare a business plan and a technical plan for the Institute. The business plan should specify the form of cooperative relationships of the Institute with the states, the private sector, and other federal agencies. The Institute should be a resource that allows existing federal agencies to execute more successfully their established regulatory and administrative responsibilities related to truck size and weight. The technical plan would not be for a single large research project that would finally resolve all questions about the relation of truck size and weight to safety and other highway costs; no such study could be conducted. Instead, the plan would set forth a process that could be relied upon at any time as an essential part of the government’s management of the highway system. The Institute should be subject to a sunset review by Congress after a specified time, possibly 6 years.

Congress should authorize the Secretary of Transportation to approve pilot studies involving temporary exemptions from federal motor vehicle size and weight regulations for vehicles operating within alternative limits, operated by motor carriers that agree to participate in evaluation of the safety and other impacts of the alternative limits. DOT should approve pilot studies upon the recommendation of the Institute, which should be responsible for planning the studies, carrying out the evaluations, observing that carriers comply with the conditions of the studies, and recommending to DOT and Congress on the basis of the results of each study whether changes in federal regulations are warranted.

In this recommendation, a pilot study is defined as a controlled experiment designed to measure the consequences of changes in vehicle dimensions, weights, or operating practices; following a scientific design; involving the collection of data under actual operating conditions; and entailing direct observation of the primary impact of interest (e.g., frequency and severity of accidents) rather than proxies (e.g., vehicle stability or driver performance) alone. It would be necessary for vehicles participating in a pilot to be in compliance with the laws of the states in which they were operated or receive approval from the states

through established permitting processes or other state action. Congress should require that, as a policy, Institute programs promote cooperative, regional, multistate solutions to size and weight problems.

Legislation authorizing a pilot program should specify the general criteria that temporary exemptions would have to satisfy to be considered for permanent status. These criteria should include demonstration in the pilot study that an exemption is consistent with public safety and the requirement that any increases in highway agency costs be covered by user fees paid by operators of the vehicles.

Federal law should allow any state to participate in a federally supervised permit program for the operation of vehicles heavier than the present federal gross weight limit, provided the state satisfies the requirements outlined below. DOT should be authorized to certify, on the advice of the Institute, that a state meets these requirements. The Institute should be responsible for monitoring the consequences of the federally supervised permit program.

The federally supervised permit program provided for under this recommendation would rationalize the present, largely uncontrolled and unmonitored system of state-issued exemptions. The recommended federal oversight would be a mechanism whereby the performance of the regulations could be evaluated and adjustments made when warranted by the evaluations and by changes in external conditions. For the first time, Congress would know the consequences of changes in regulations. Improved information, together with greater facility to adjust regulations when necessary, would lead to regulations that more effectively promoted safety and controlled highway transport costs.

The permit program, implemented with federal oversight of safety, fees, and enforcement, would constitute a redefinition of the federal role in truck size and weight regulation. The federal government would have diminished involvement in defining numerical dimensional limits, but greater responsibility for ensuring that state regulations governing the use of vehicles on federal-aid highways were contributing to the attainment of national objectives. In effect, federal oversight would tend toward performance standards: states could propose solutions to problems, and the federal government would then assess whether the proposals met qualitative objectives. Federal regulation, by requiring states to justify their proposals on performance grounds, would continue to provide a buffer protecting state

highway programs from local, short-term economic pressures to depart from best management practices.

The opportunities created by the permit program would be expected to stimulate new multistate agreements on truck size and weight. Federal administration of the program should promote or require consultation among neighboring states. Expansion of regional agreements would constitute further evolution toward more rational standards and away from arbitrary state-to-state variations.

Recommended size and weight provisions of the permit program are as follows:

• The states should be allowed to issue permits for operation, on any road where the use of such vehicles is now prevented by federal law, of

  • Six-axle tractor-semitrailers with maximum weight of 90,000 lb; and

  • Double-trailer configurations with each trailer up to 33 ft long; seven, eight, or nine axles; and a weight limit governed by the present federal bridge formula.

• After a transition period, all trucks operating under grandfather exemptions or state-specific exemptions from federal rules (when operating on roads where they could not be legally operated without such exemptions) should be made subject to the monitoring and evaluation requirements that would apply to trucks in the proposed new federally supervised permit program. Reliable information obtained in this way on the impacts of grandfather operation would allow Congress to decide whether the grandfather provisions should be altered or additional permitting flexibility should be extended to all states.

The recommended permit vehicle specifications are not presented as the optimum regulation. The definitions of the vehicles eligible for permitting would be subject to revision over time. Federal review of the performance of the permitting program would be permanent and ongoing, and the program’s results would guide revision of the limits. Revisions would most suitably be instigated by recommendation of the Institute, following the procedures outlined in Recommendation 2.

Enforcement A legislatively defined joint federal–state program for enforcement under the permit program should include the following four elements:

• Formal and effective performance monitoring of enforcement functions.

• Application of new enforcement tools, which may include imposition of federal penalties for violation of federal limits. Congress should consider requiring, as a precondition for state participation in the permit program, that the state enact enforcement provisions to effectively hold accountable the parties responsible for placing overweight loads on the highways and to target repeat violators. Such provisions might include information systems that would make possible identification of responsible parties and repeat offenders, as well as “relevant evidence” statutes.

• Adequate enforcement funding, including federal contributions derived from user fee revenues.

• A program to advance the application of information technology as an enforcement tool.

User Fees Legislation creating the permit program should specify a quantitative test for the revenue adequacy of the permit fees imposed by participating states. As far as possible, fees should be structured to avoid giving truck operators incentives to use truck configurations whose public costs exceed their private benefits. Fees should at least cover estimated administrative and infrastructure costs for the program when it is at its steady-state level, but proposals from states for fees that reflect other external costs or benefits, supported by well-reasoned arguments, would be acceptable. States that decide to participate in the program should be required to provide DOT with the data necessary to verify revenue adequacy.

Safety Requirements As a temporary measure, equipment requirements developed in the most rigorous existing state permit programs should be imposed on permit recipients. Requirements should be proposed by the states that apply to participate and should be reviewed by the Institute and approved by the Secretary. The requirements proposed could be more stringent than any existing requirements if the state provided a rationale for them. Their im-

plementation should be coordinated with the Institute’s research on safety countermeasures.

Bridge Management A state where larger trucks come into use through the permit program will need a plan for cost-effectively alleviating constraints on the vehicles’ use due to deficient bridges. The DOT responsibility for certifying that permit fees cover program costs implies the need to evaluate each participating state’s management of the bridge costs of the larger trucks. The state application for participation in the permit program should include a plan for managing bridge impacts.

Federal law should allow operation of longer combination vehicles under the provisions of the federally supervised permit program outlined in Recommendation 3 and participation of these vehicles in pilot studies according to the procedures outlined in Recommendation 2.

The committee does not see justification at this time for any general revision of the specifications in federal laws and regulations regarding the networks of roads to which the various federal dimensional regulations are applicable. In particular, there does not appear to be justification for extending federal weight regulation to the non-Interstate portion of the National Highway System (that is, the system of principal arterial roads designated by federal law), where state regulations now govern most aspects of truck operations.

New enforcement mechanisms must be instituted and a plan for evaluating the safety effectiveness of route restrictions developed before any new federal regulations regarding truck operations on restricted networks of roads are enacted.

The preceding recommendations call for three kinds of activities involving data analysis and research: systematic monitoring of truck traffic and truck costs to evaluate regulatory effectiveness, basic research on the relationship of truck characteristics to highway costs, and pilot studies to test new vehicles. The following are specific topics requiring research. Research on these topics should be conducted at congressional direction by the Institute (if a study topic is essentially related to

an established responsibility of a DOT agency, the study should be conducted cooperatively by the Institute and that agency):

• Evaluation of the effectiveness of the enforcement of size and weight regulations,

• Air quality impacts of changes in truck characteristics,

• Relation of truck performance to crash involvement,

• Risk-based bridge costs,

• Freight transportation market research,

• Costs of mixed automobile and truck traffic arising from nuisance and stress, and

• New infrastructure development and truck-only facilities.