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Policy Issues

Truck Size and Weight

Truck weight limits on the Interstate Highway System were set at 80,000 pounds by Congress in 1982; truck length and weight limits for longer combination vehicles (LCVs) — tractors with two or more trailers weighing more than 80,000 pounds—were frozen in 1991. These limits were imposed largely because of concerns about the safety of longer and heavier trucks and the uncompensated highway damage they cause. These concerns are still valid.

The fuel taxes and other highway-related fees that heavy trucks pay do not come close to covering the costs of the highway damage they cause. According to the U.S. Department of Transportation’s (DOT) 2000 Highway Cost Allocation Study​, an 80,000-pound, five-axle combination truck pays just 80 percent of its cost responsibility; a six-axle, 97,000-pound truck pays just 50 percent. These percentages are not significantly different today.

​​In fact, recent studies suggest that 80,000-pound trucks today underpay their federal cost responsibility by around 27 cents per gallon. For other truck size and weight configurations, the federal underpayment could be as high as $1.17 per gallon.

These huge underpayments mean that much of the damage heavy trucks cause is paid for by the general public. Proponents of heavier trucks claim they support higher taxes to pay for the additional damage those trucks would cause. However, the additional taxes they say they are willing to pay are far less than what is needed to compensate for existing underpayments, much less the additional underpayments heavier trucks would cause.

In addition, because many parts of the interstate highway system were not built for longer and heavier trucks, their widespread use could require massive new spending to strengthen or replace bridges and pavement, as well as to widen vehicle lanes and shoulders.

In June 2015, the DOT released a report examining the impacts of increasing current federal truck size and weight limits. The DOT study concluded that no changes to existing truck size and weight limits should be made at this time. Among other things, the study noted that if federal truck weights were increased to 91,000 pounds, more than 4,800 bridges would need to be strengthened or replaced because of added stress, at a cost to taxpayers of more than $1.1 billion. The DOT analyzed just 20 percent of the nation’s bridges for its report — the remaining 80 percent are probably even more vulnerable to heavier trucks.​​