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Supply Chain News: Waiting for US to Approve Longer and/or Heavier Trucks on US Highways? Don't Hold Your Breath


Report from National Academies of Science Details Huge Research Agenda to Create Data Needed to Make the Decisions

April 24, 2018
SCDigest Editorial Staff

For many years now, shippers and some – repeat some – carriers have been pushing for US federal transportation rules to allow heavier and/or longer trucks.

Specifically, one proposal is a move to allow full truck weights to reach 97,000 pounds, up from 80,000 currently, with the additional of a sixth axel/brake to maintain safety. This would allow shippers that currently "weigh out" before they cube out to get more goods in each load.

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Will all that research get done in our lifetimes? Perhaps, but clearly not any time soon, likely for many years.

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The other is to allow twin 33-foot cargo trailers from the maximum 28-foot length currently allowed.

Proponents say both changes would reduce transport costs, improve safety by taking many trucks off the road, help address the driver shortage, and reduce CO2 emissions. Each proposal is supported by a different lobbying groups. The Coalition for Transportation Productivity was created under the leadership of the then Kraft Foods and other shippers to push for the heavier truck rule.

The group pushing for the longer twin 33-foot trailers is called Coalition for Efficient and Responsible Trucking, supported by both shipping and some carrier interests, especially in the parcel sector.

At various times it has appeared one or both proposals might make it into law, especially in recent years the longer trucks change, but hopes have been consistently dashed – sometimes at the last minute.

In 2012, for example, railroad industry backing led to creation of a brilliant campaign that had local sheriffs from hundreds of counties communicate with their local US representatives to express their opposition to the heavier trucks on safety grounds right before legislation was coming to a vote. The language to allow heavier trucks never made it into the final transportation bill.

It hasn't helped that carriers have gone from "squishy" about the changes to downright opposition in many cases.

During its 2016 convention in Las Vegas, for example, the Truckload Carrier Association (TCA) officially changed its policy stance, saying it wanted to maintain the current five-axle, 80,000-pound weight restriction, even though in recent years it, like the larger American Trucking Associations, had supported the change for heavier trucks. The TCA is also decline to back the twin 33's.

Why? Truckload carriers are worried that allowing the heavier trucks would in the end result in them simply hauling more freight per load for the same basic cost. On the twin 33's, truckload carriers would see little benefit, as they use single trailers, but it would be an advantage to some less-than-truckload (LTL) carriers, perhaps making their costs and service more competitive with truckload.

Add to all those obstacles a seeming mountain of research a new report says needs to be completed before legislators should consider either change.

Back in April 2016, the Department of Transportation delivered to Congress a final report on its Comprehensive Truck Size and Weight Limits Study, which had been mandated by the MAP-21 highway bill of 2012.

Now, two years later, an advisory panel of the National Academies of Science, Engineering, and Medicine (NAS) has issued an interim report on the research it will recommend needs to be completed. The 2016 study, the new report says, couldn't really deliver on its mission due to a lack of data, with the 2016 study conclusion being that there was not enough data to support either change in policy.

What is needed is more research, NAS says – lots and lots of it.

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Research is needed in five many categories: safety, enforcement, modal shift, bridges, and pavement. To give readers some idea of the scope of the research needed in each area, below is the list of candidate topics for just one of those areas, the impact of size and weight limit changes on pavement:

1. Determine the capability of current methods to produce appropriate pavement designs if trucks with maximum axle weights and configurations substantially different from the present ones come into use. Identify the most appropriate techniques for such applications.

2. Develop a method of projecting pavement performance that accounts for the characteristics and distribution of tire contact stresses.

3. Develop performance prediction models that allow consideration of the effects of changes in truck size and weight limits, as well as changes in the axle configuration, and that are applicable to the common types of actual pavements, including overlay pavements, on US roads.

4. Evaluate the effect of dynamic loading on pavements and the relation of dynamic loading to the effect of truck traffic on pavement life.

5. Develop a method of predicting the increase in pavement distresses in local roads (and associated costs) due to changes in truck size and weight limits, taking into account limited data availability and variability in local highway agencies' construction and maintenance practices.

6. Demonstrate methods for taking into account uncertainties in pavement analysis and design in decision making on truck size and weight limits and for communicating the reliability of estimates to decision makers. Pavement analysis and design have many inherent uncertainties, such as uncertainties in material characterization and in weigh-in-motion data collection.

7. Develop methods to project how the adoption of heavier vehicles would impact pavement service life, cost, and environment through life-cycle assessment. The heavier vehicles will develop higher structural responses within the pavement; however, the number of load repetitions is expected to decrease for a given quantity of goods carried.

8. Assess how truck platooning (through the application of connected vehicle technology) would affect pavement performance and costs and how such effects can be controlled.

9. Determine the impact of changes in truck loading and axle configuration in unbound layers of pavements, especially on low-volume roads.

There are similar detailed research agendas for each of the other four main categories, with 45 topics in total. NAS says will next make recommendations on how to conduct the research deemed necessary to make an informed decision on increasing the 80,000-pound limit.

Will all that research get done in our lifetimes? Perhaps, but clearly not any time soon, likely for many years.

So those hoping for her heavier or longer trucks are likely to be waiting for a long time before they see any changes – and that only if the research when it is finally complete is favorable for one or both of the proposals

Do you think we will see changes to allow heavier or longer trucks any time soon? Let us know your thoughts at the Feedback section below.


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