TRB Study Summary

The Transportation Research Board's research committee, working at the request of Congress recommended an increase in the maximum allowable weight of six-axle semitrailer combinations. The study was released on May 16, 2002 and can be read in its entirety by clicking here or on the link to the left.

Under the TRB proposal, the maximum allowable weight of tractor-trailer combination vehicles would be increased to 90,000 pounds from the current cap of 80,000 with the addition of a sixth axle. The committee wants state governments to authorize tests of the heavier trailers so the U.S. Department of Transportation will have an abundance of data to analyze in evaluating the suggested policy's safety and economic efficiency implications.

Furthermore, the committee wants Congress to create a new institute within the Department of Transportation to evaluate and monitor the state pilot programs and make policy recommendations to the department's secretary and the national legislature. One of the possible pilot programs discussed within the TRB study was to allow six-axle 97,000-pound tractor-trailers on the National Highway System (the ASET proposal).

The following quotes and facts can be found within the overall study and make the case for allowing heavier, safer, more productive trucks in states that wish to take advantage.

FEWER ACCIDENTS & LESS ROAD WEAR

The TRB estimated that the "total annual mileage of large trucks would decline by more than 3 percent compared with traffic volume if the federal limits were not changed." Because of these projected levels of use, "annual freight transportation costs were projected to decline by $5.2 billion (in 1995 prices and freight volumes) or 2.6 percent of the prior total cost of truck freight transportation." Clearly the fact that fewer trucks would be used to haul the same amount of product would help our highway infrastructure in the years to come.

Most importantly, the TRB unequivocally declared, "Accident losses were projected to decline because the reduction in truck-VMT would more than offset any greater risk per mile of travel of the new trucks compared with the vehicles replaced."

INTERNATIONAL COMPETITION & CONGESTION

International competition and the constraint of our congested highways and intermodal sites were also stated as leading reasons for the increased weight threshold. The TRB study said, "U.S. weight limits are lower than the limits of most of the nation's trading partners and heavier six-axle semitrailers…would be well suited to carrying international containers. Indeed, the benefits of increased truck productivity may appear more attractive today because of emergent concerns over capacity constraints throughout the freight transportation system." This is particularly important, as the Department of Transportation has predicted an increase in freight movement of 87% by the year 2020 over existing levels. Congestion is at an all-time high, resulting in over 36 hours of waiting time (three times the waiting periods compared with 20 years ago). If congestion and international trade continue as expected, our highway system will be in a state of total gridlock soon.

BRIDGES

In addition to the change in overall gross weight, the study indicated that there is an inherent problem with the existing bridge formula in the U.S. Because of the complicated and confusing formula, anti-productivity forces in the past have maintained that heavier trucks could not legally travel on bridges within the Interstate system. Citing the restrictive nature of the bridge formula, the TRB recommended either a simpler plan that would exempt six-axle heavier trucks so that they might be able to traverse the National Highway System or potentially, at a later date, simply replace the current bridge formula with one that is more universally accepted.

The study also addressed the concern in former studies that the cost of bridge damage (by allowing heavier, six-axle trucks) would be extremely high. "[I]t would be feasible to maintain or reduce the risk of bridge failures at lower cost than these studies' estimates through more intensive inspection and maintenance of bridges, routing restrictions, and more effective enforcement."

IN SUMMARY

As ASET has consistently stated over the past few years, by allowing safe six-axle tractor-trailers, the highways will be safer, and motor carriers, shippers and ultimately the consumers will all benefit from the increased productivity. While ASET has argued for a more efficient, 97,000-pound six-axle truck, the TRB study agrees with almost every single statistic and conclusion that ASET has argued would occur from allowing states the opportunity to utilize more productive vehicles. Whether it is fewer accidents, decreased congestion, less road damage, better international competition, or helping to reduce pollution, six-axle trucks can help address several growing problems threatening to cripple our National Highway System.

The Transportation Research Board has joined the ever-growing number of companies, associations and independent groups advocating for a change in truck weight policy and the time has come for Congress to act. ASET welcomes this positive development from such a well-respected, non-partisan group.