Let larger trucks operate on interstates but monitor safety, costs, says report

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 Research Council's Transportation Research Board. This council is the main operating arm of the National Academy of Sciences and the National Academy of Engineering.

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, the report says.

Since the federal government pays 90% 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 past 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 make recommendations.

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 interstates to use secondary roads where accidents are more likely to happen and maintenance costs are higher. States and Congress also are granting more exemptions that let certain larger trucks travel on interstate highways.

States should be allowed to issue permits for 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 with 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.

Double trailers as long as 33 feet each should be permitted, making the trailers 5 feet longer than common 28-ft double trailers, the report says. Two 33-ft 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-lb tractor-trailers should only be operated in states that choose to allow them, and only by carriers that receive 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.

The report also recommends that Congress authorize pilot studies. Trucking companies that agree to participate in evaluations of safety and infrastructure costs of alternative limits would be temporarily exempt from federal size standards for trucks.

Also, the committee urged Congress to charter an institute to monitor the new permit program, conduct pilot studies, and carry out research on impacts of truck traffic. Based on its evaluations, the institute should recommend changes in federal regulations to Congress and the secretary of transportation. Objective data collection and analysis, coupled with public comment, should help break the gridlock over size and weight policies.

Technologies are available for improving truck safety, but more research and monitoring is needed, the report said.

The committee said truck size regulations affect international commerce, too, since Canadian and Mexican size and weight limits differ. Containers shipped in international trade often are not consistent with US size regulations for transport on land.

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