New report calls for allowing heavier trucks on Interstate highways

May 28, 2002
The federal government should authorize states to allow trucks exceeding present federal weight limits to operate on interstate highways, provided that

The federal government should authorize states to allow trucks exceeding present federal weight limits to operate on interstate highways, provided that impacts on safety and road-maintenance costs are monitored, says a new report from the National Academies' Transportation Research Board (NATRB). Congress should charter a new federal organization to oversee implementation of federal regulations and evaluate their results, carry out pilot studies and research to determine the impact of trucks on highways, and recommend new regulations based on its findings.

Since the federal government pays 90 percent of the costs to construct and maintain the interstate highway system, its regulations are designed to limit wear and tear from heavy vehicles. Despite advances in technology and changes in traffic and highway conditions, federal truck regulations have been significantly revised only twice in the last 45 years. Concerns about the safety of larger trucks and their impact on state highway budgets and freight industry competition have deterred Congress from acting. To guide future policy decisions, Congress asked the National Research Council to study the regulations governing truck size and make recommendations, according to NATRB.

"We discovered a lack of information about the costs and benefits of larger trucks and the impact of regulations," said James W Poirot, chair of the committee that wrote the report, and chairman emeritus, CH2M Hill Ltd, Mukilteo WA. "To determine and enact limits that are based on facts, the nation needs a program that observes and evaluates the consequences of truck traffic. By following this path, Congress would be able to know the real impact of changes in truck-size regulations for the first time."

Trucks handle about half of the tonnage carried between cities in the United States. With bigger vehicles, freight can be moved at lower costs. But given federal size limits, larger trucks sometimes bypass interstate highways--the safest and most efficient roads--to use secondary roads where accidents are more likely to happen and maintenance costs are higher. In addition, states and Congress are granting growing numbers of special exemptions that let certain larger trucks travel on interstate highways, a trend that is eroding federal standards, according to NATRB.

States should be allowed to issue permits for the operation of six-axle tractor-trailers weighing up to 90,000 pounds, the report says. The current federal limit is 80,000 pounds, and the standard tractor-trailer has five axles. Compared to the five-axle truck, the six-axle truck reduces shipping costs moderately, and its lower weight-per-axle ratio cuts down on pavement wear. However, increasing the total weight of trucks increases bridge construction and maintenance costs, NATRB says.

Double trailers as long as 33 feet each should be permitted, making the trailers five feet longer than the 28-foot double trailers that are most common today, the report says. Two 33-foot trailers can turn at intersections without encroaching any farther on opposing lanes than tractor-trailers, and may be more stable than shorter double trailers. These double trailers and the 90,000-pound tractor-trailers should only be operated in states that choose to allow them, and only by carriers who receive special permits from the states, added the committee. Participating states would be required to meet federal standards regarding enforcement, fees paid by permit recipients, safety requirements, and management of effects on bridges.

In addition to the new program for operation of larger trucks with special permits, the report also recommends that Congress authorize pilot studies. Trucking companies that agree to participate in scientific evaluations of safety and infrastructure costs of alternative limits would be given temporary exemption from federal size standards for trucks.

The committee called on Congress to charter an institute to monitor the new permit program, conduct the pilot studies, and carry out basic research on the impacts of truck traffic. These activities do not match the responsibilities of any existing federal agency. Based on its evaluations, the federal institute should recommend changes in federal regulations to Congress and the Secretary of Transportation. Objective data collection and analysis, coupled with full public comment, should help break the gridlock over size and weight policies.

Promising technologies are available for improving truck safety, but more research and monitoring is needed, the report said. For example, using an electronic braking system that could sense instabilities from sudden evasive maneuvers might improve the truck's ability to stop quickly and maintain control. The proposed pilot studies and permit program could provide incentives for industry and states to develop safety-related innovations.

The committee noted that truck-size regulations affect international commerce as well, especially since Canada and Mexico, free-trade partners with the United States, have different size and weight limits, complicating cross-border traffic. In addition, containers shipped in international trade often are not consistent with US size regulations for transport on land.