The railroad industry has challenged a report that recommends that the United States allow longer and heavier trucks on the nation's highways.

In a report issued last May (Special Report #267), the Transportation Research Board (TRB), a unit of the National Research Council, said that the federal government should authorize states to permit trucks exceeding federal weight limits to operate on interstate highways, provided that safety and road-maintenance costs were monitored. The study was required under the 1998 Transportation Equity Act for the 21st Century.

But in an analysis commissioned by the Association of American Railroads, Dr. Gerald J. McCullough, an associate professor of applied economics at the University of Minnesota and a senior consultant with Charles River Associates, criticized the TRB report as being flawed and of "extremely limited usefulness." McCullough was particularly critical of the research's limitations in focus, writing, "The narrow analytical perspective significantly limits its usefulness to national transportation policy."

At present, federal law limits five-axle tractor-trailers to a gross weight of 80,000 pounds on interstate highways. The TRB report suggested that states be allowed to issue permits for the operation of six-axle tractor-trailers weighing up to 90,000 pounds. Compared to the five-axle truck, the report said, the six-axle version affords a lower weight-per-axle ratio, which cuts down on pavement wear.

The TRB report also suggested that double trailers as long as 33 feet each be permitted. Currently, each unit in a double trailer measures 28 feet in length. According to the TRB, two 33-foot trailers could make turns at intersections without encroaching any farther on opposing lanes than do current tractor-trailers. In addition, the report said, 33-foot trailers may be more stable than today's 28-foot trailers.

Along with those controversial recommendations, the TRB called for the creation of a new federal organization that would oversee implementation of federal regulations and evaluate their results. It also recommended that the federal government conduct pilot studies on the usage of 33-foot doubles.

Those suggestions, however, did not sit well with McCullough. He suggested that the TRB's proposal to introduce larger trucks immediately, coupled with follow-on pilot programs to monitor their impact, would make highway users unknowing participants in an experiment testing the safety of larger double trailers.

The economist further charged that the TRB report failed to recognize that truck size and weight regulations should not focus solely on lowering costs for motor carriers and some shippers. Rather, he contended, they should focus on minimizing the public costs of truck transportation and ensuring the overall efficiency of the national freight transportation market. "An efficient market," he said, "is one in which the users absorb the full marginal costs that they impose."