Can our roads handle heavier loads?

Posted by Harriet Mills on May 5, 2016 2:45:20 PM

Regulation changes to allow heavier trucks on the interstate system failed to make it past Congress last fall. Within the trucking industry, a vigorous debate emerged as to who would win and lose, and raised some important questions about the consequences to highway conditions should bigger loads be allowed.

The SAFE (Safe, Flexible and Efficient) Trucking Act would have allowed tractor trailers to have as many as six axles, up from five, and to increase their maximum weight from 80,000 to 91,000 pounds.

DOT Study InfographicShippers and logistics firms applauded the proposed changes, saying that lifting the truck weight limit on federal roadways would result in fewer trucks on the road, make shipping more efficient and competitive with Canada and Mexico — countries that already have higher weight limits in place. In addition, it would bring some relief to the truck driver shortage in the U.S., which is to the tune of 48,000 drivers, according to the American Trucker Association.

But, in a letter to Congress, the Trucker Carriers Association says lifting the axle limit would require costly rig upgrades — kingpins, tires, trailer reinforcements, engine adjustments and more. The estimated price tag: $8,000 to $24,800 per tractor trailer. Overall fuel consumption would go down, however, an additional axle on a tractor trailer would decrease a rig’s fuel economy by 0.5 miles per gallon, even with empty loads.

As for the impact on the roads, supporters say adding an axle would result in a lower weight distribution per axle. That, along with fewer trucks on the road, would reduce wear on roads and bridges. A study from the U.S. Department of Transportation shows a 4.2 percent reduction in pavement costs with the bigger, heavier loads, says Coalition for Transportation Productivity. And, the DOT has stated these loads would meet weight-distribution requirements on bridges.

The figures in the infographic above come from the DOT’s Comprehensive Truck Size and Weight Limits Study, and the final report was released in April.

The bigger loads resulted in an increase in one-time costs for bridges by $1.1 billion. Crash data was analyzed in the state of Washington, which saw a 47 percent increase in crashes and a 20 percent increase in braking violations.

In spite of some of these encouraging findings, the DOT recommends that lawmakers hold back on changing federal truck sizes and weights. That’s because the study’s model and data limitations were “so profound,” it could not predict the impact of these heavier loads with any reliability.

Is it time for the federal government to allow heavier trucks? Tell us what you think. 

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