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National Academies of Sciences Outlines Path Forward For Study Of Twin 33s

National Academies of Sciences Outlines Path Forward For Study Of Twin 33s

The National Academies of Science has identified seven core research areas that it said could help DOT determine possible changes to truck size and weight. (Photo:

In 2015, the Department of Transportation (DOT) released a long-awaited truck size and weight study. The report, heralded by safety groups and panned by industry groups such as the American Trucking Associations (ATA) and shippers, did not provide any clarity on the matter of larger or heavier trucks. Instead, it kicked the can down the road.

DOT essentially conducted a four-year study to determine there wasn't enough data to move forward with changes to truck size and weight regulations.

"At this time, the department believes that the current data limitations are so profound that the results cannot accurately be extrapolated to predict national impacts," said then-DOT Under Secretary Peter Rogoff. "As such, the department believes that no changes in the relevant truck size and weight laws and regulations should be considered until these data limitations are overcome."

At the heart of the matter is twin 33-foot trailers, which would add 10 feet of cargo capacity to the current 28-foot trailers.

Fast-forward three years and debate is still ongoing over the potential benefits – or harm – that 33-foot trailers could do. A new report from the National Academies of Sciences, Engineering, and Medicine (NAS) sheds little light on whether longer trailers are warranted, but it does outline the steps DOT should take to collect the data the agency said it was lacking in 2015.

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Asked by DOT to create a roadmap forward, NAS developed a report that identifies 7 core research projects that could assist in drawing more definitive conclusions on longer trucks. A committee for NAS estimates it would take between $4 million and $6 million and four to six years to complete these "core research tracks."

DOT is not obligated to follow NAS' recommendations.

Those tracks are:

  • Development of a truck traffic, weight, and configuration database from nationwide weigh-in-motion installations and other sources.

  • Development of a freight market model for estimating the effect of changes in truck size and weight regulations on shippers' choices of freight mode and truck size.

  • Development of pavement analysis methods for heavier axle limits, multiaxle groupings, and alternative tire and suspension types.

  • Development of a model of the relationship of bridge deterioration and service life to vehicle loads.

  • Comparative evaluations of crash risks of alternative configurations based on traffic and crash data.

  • Development of protocols for evaluating the performance of configurations with simulation, track testing, and field trials.

  • Measurement of relationships between frequency of overloads and enforcement methods and level of effort.

Completing these research programs, NAS said, would "strengthen the federal and state governments' capabilities to project impacts of changes in truck regulations. Of equal importance, the research could reveal opportunities to improve safety and productivity and control highway costs, regardless of whether truck size and weight limits are changed."

Industry groups and shippers have long pushed for longer tractor-trailer combinations that they say will increase productivity without jeopardizing safety.

The Truck Safety Coalition, a joint group of Parents Against Tired Truckers and Citizens for Reliable and Safe Highways, claims that the longer 33-foot doubles would actually extend 17 feet longer than a current 53-foot tractor-trailer and have worse crash rates. Citing a study by the Multimodal Transportation & Infrastructure Consortium (MTIC), it said that double-trailer configurations have an 11 percent higher fatal crash rate than single-trailer trucks. The group also cites a 22-foot longer stopping distance and increased damage to roadways as negative impacts.

In a letter to Congress earlier this year, more than two dozen interest groups reiterated some of the Truck Safety Coalition's arguments against longer trailers.

"Increasing the length of double tractor-trailers by five feet per trailer would result in a configuration that is approximately the size of an 8-story building. These massive trucks would not only be more difficult for other motorists to maneuver around and co-exist on the roadways with but would also be more difficult for truck drivers to operate," the group's letter stated. "For example, ‘double 33s' traveling at 60 miles per hour require an additional 22 feet to stop compared to existing twin-trailer configurations. Considering crashes in which a truck rear-ends a passenger vehicle have gone up 82 percent from 2009 to 2015, any extra stopping distance will make such crashes more likely and increase the severity of the crashes that are already occurring. Claims that longer trucks will improve safety ignore the facts and defy reality.

"Despite misleading assertions to the contrary, longer or heavier trucks will not reduce the number of trucks on our roads or the number of truck vehicle miles traveled or the number of truck crashes," the letter continued. "In fact, the U.S. Department of Transportation found that any reduction in the number of trucks due to a truck size increase would be offset within a year of implementation. An increase in trailer size or weight limit would divert freight from the rails to trucks, as the latter industry will have a greater capacity to ship via longer or heavier trailers – thereby disrupting and diminishing intermodal efficiency."

Americans for Modern Transportation, an advocacy group that includes XPO Logistics Inc (Nyse: XPO), PODS, Manufacture Alabama and Truck Trailer Manufacturers Association, FedEx Corporation (Nyse: FDX), United Parcel Service, Inc. (Nyse: UPS), WYRC, and Inc (Nasdaq: AMZN) and the U.S. Chamber of Commerce among its members, countered the arguments by noting that extending trailers from 28 to 33 feet would save 3.1 billion vehicle miles traveled per year, result in 4,500 fewer truck crashes, and save 52.3 million hours due to less highway congestion.

"With fewer miles traveled, the LTL industry would use less fuel — conservative estimates show a 255-million-gallon reduction in annual diesel fuel use. That is a lot of crude that is not drilled, transported, refined, transported again and burned to power the LTL fleet," it claimed. "Furthermore, a five-foot extension for twin trailers, with no change in the weight limits, would result in 2.9 million fewer tons of carbon emissions."

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The preceding article is from one of our external contributors. It does not represent the opinion of Benzinga and has not been edited.

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