Monday, October 23, 2017

Group says DOT's 6-axle truck data flawed

Wednesday, July 15, 2015
The Coalition for Transportation Productivity says some of the crash data used by the U.S. Department of Transportation in its truck size and weight study was flawed.
The Coalition for Transportation Productivity says some of the crash data used by the U.S. Department of Transportation in its truck size and weight study was flawed.

WASHINGTON — The Coalition for Transportation Productivity (CTP), a group of nearly 200 of the nation’s top manufacturers, shippers, carriers and allied associations, Tuesday delivered testimony urging the federal Transportation Research Board to examine truck weight safety data contained in the U.S. Department of Transportation’s Comprehensive Truck Size & Weight Limits Study.

In his testimony, CTP Executive Director John Runyan highlighted what he said were several flaws associated with state-level data suggesting a higher crash rate for six-axle trucks — a conclusion referenced by DOT in its cover letter to Congress recommending against truck weight changes.

While Runyan noted that DOT’s technical findings correctly state that heavier, six-axle trucks would lead to reduced logistics costs, fuel consumption, emissions and congestion, he pointed to data suggesting that DOT officials have actually underestimated reductions in vehicle miles traveled, and thus may have also underestimated reductions in costs, vehicle congestion and environmental impacts.

“Given the presence of important information, such as the important actual vehicle testing results and the fact that heavier six-axle vehicles are safely used in a number of states and other countries, it seems that the Technical Report gives too much emphasis to certain crash data which the U.S. DOT self-describes as nationally statistically insignificant and subject to many limitations and assumptions,” Runyan testified. “Our assessment of the Technical Report finds the available information to be sufficient to support authority for states to allow interstate system use of the heavier, six-axle study configurations.”

Runyan said the study strongly points to the ability of six-axle truck weight reform to safely help minimize congestion, pavement wear and the environmental impact of trucking.

In his remarks, Runyan called attention to the following specific issues:

• Some of the crash data may have been based on the performance of a six-axle vehicle that is substantially different from the six-axle configurations designated for study. 

For example, the study references higher crash rates for heavier, six-axle vehicles operating in the state of Michigan, yet those vehicles are a different configuration than what the DOT set out to study.

• The heavy reliance on weigh-in-motion data to estimate vehicle miles traveled may have resulted in undercounting of six-axle vehicles, thereby increasing their reported crash rates.

For example, Runyan said many six-axle trucks utilize a “lift axle,” which is not often detected by weigh-in-motion sensors. As a result, the six-axle vehicles are likely undercounted, thereby overstating their crash rate and underestimating vehicle miles traveled.

Runyan said CTP supported carefully crafted truck weight reform giving each state the option to set higher interstate weight limits only for trucks equipped with six axles rather than the typical five. Because one-quarter of U.S. truck shipments meet the current interstate weight limit with space left in the trailer, this proposal would allow companies to meet demand with fewer vehicles and make the U.S. transportation network more efficient, especially as gross domestic product and population continue to grow.

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