Freight-Shipping: How Big Should Big Rigs Be? – DTN

Federal law says the maximum allowable weight for freight-shipping trucks is 80,000 pounds, although some states have higher limits that were grandfathered in when the federal rule was passed. The U.S. Department of Transportation (USDOT) has been studying allowing an increase of that maximum weight to 91,000.

On October 5, the Transportation Research Board (TRB) published a review of the USDOT’s “Comprehensive Truck Size and Weight Limits Study” and found some areas lacking.

The TRB stated that, “… a more comprehensive and useful response would have been possible.” The TRB continued, the study “… lacks a consistent and complete quantitative summary of the alternative configuration scenarios, and major categories of costs — such as expected bridge structural costs, frequency of crashes, and infrastructure costs on certain roads — are not estimated.”

The USDOT report should have provided a framework for understanding all the costs and benefits, TRB stated. “A comprehensive list of the categories of costs and benefits, the features of the hypothesized regulatory change that influence each category, the direction of change, and the categories that are likely to be critical to the evaluation all can be identified from results of the present and past studies.”


The Soy Transportation Coalition (STC) also did a study on increasing truck weights which was funded by the soybean checkoff. Executive Direct Mike Steenhoek told DTN that trucking and rail are increasingly not interchangeable modes of transportation.

“This is particularly the case with agriculture. Over the past several decades, railroads have adopted a business model of emphasizing long haul service, which has resulted in limiting access to the rail network in rural areas. Years ago, every soybean and grain handler enjoyed rail service at their facility. That is no longer the case.

“As a result, farmers and grain handlers must increasingly utilize trucking to access the rail network. Given how trucking and rail are less interchangeable, the potential modal shift from rail to trucking due to the adoption of 91,000 lbs. semis is significantly limited. The U.S. Department of Transportation calculated that the potential modal shift nationwide would amount to less than one third of one percent of railroad revenues. This minimal modal shift would be even less for agricultural shipments,” said Steenhoek.

Bob Zelenka, executive director of the Minnesota Grain and Feed Association told DTN,

“We have been generally supportive of increased truck weights since the U.S. government took control of truck weight and length in the early 1980s. At that time, the feds grandfathered in states that had weights that exceeded the federal 80,000-pound limit. Unfortunately and contrary to a few of our neighbors, Minnesota was still at the 80,000 pound limit at that time.

“In 2008, the Minnesota Legislature passed a law allowing permits to be issued for ‘raw and unprocessed agricultural commodities’ to be hauled at 90,000 pounds with six axles and up to 97,000 pounds on seven axles.

The fuel savings were a big part of the reasoning, through reduced trips to haul the same amount of product. However, one does wonder if real savings do occur, when figuring the cost of a new six- or seven-axle trailer, plus the $300 to $500 state permit fee and with some counties also charging a fee to travel overweight on their roads.”

An elevator manager in eastern North Dakota told DTN that the biggest benefit to farmers would be that higher weight limits “lessen the work load. What was once hauled in 10 trucks can now be hauled in nine. That means less hours.”


The state of Michigan’s truck weight laws allow more than the federal limit spread out over more axles.

“Michigan has a unique system of truck-weight laws, which allows greater maximum gross vehicle weight (GVW) than in other states,” according to The Michigan DOT, Bureau of Transportation Planning, Intermodal Policy Division.

“Gross vehicle weight includes the weights of the truck, cargo carried, fuel, and driver. Maximum allowable axle loadings are the same in all states, including Michigan. Michigan and several other states allow gross vehicle weights greater than 80,000 pounds, when spread over more than five axles. These weight laws are allowable under ‘grandfather clauses’ in federal law, but if these laws are repealed, they may not be re-enacted.

“The maximum gross vehicle weight allowed on a ‘federal-weight-law truck’ is 80,000 pounds, with four of its five axles carrying 17,000 pounds each and the steering axle carrying 12,000 pounds. The calculated maximum allowable gross vehicle weight on the heaviest ‘Michigan-weight-law truck’ is 164,000 pounds, which can only be achieved by use of 11 properly-spaced axles.

Most of these axles carry only 13,000 pounds each. The alternative to a single Michigan combination carrying 160,000 lbs. on 11 axles is two standard trucks carrying 160,000 lbs. on 10 axles. Pavement research has shown that these two smaller trucks actually cause about 60% more pavement damage than does the single heavier truck, because of their higher axle loadings and the extra weight of additional tractors at about ten tons each.”

States and provinces bordering Michigan also allow certain vehicles heavier than the federal weight law trucks. Ontario allows nine-axle vehicles carrying a total of 140,000 pounds. Ohio, Indiana, and Wisconsin issue permits allowing heavier Michigan-style trucks to travel on selected highways. This allows access by Michigan shippers to the steel industry in Gary, bulk rail and marine terminals in Toledo, and the forestry industry in northern Wisconsin. Other states along the Canadian and Mexican borders increasingly allow heavier trucks from their neighboring countries.

The Michigan DOT believes that state’s truck weight law is based on sound research and results in less highway damage and improved safety relative to federal weight law. “Several of this state’s key industries benefit by being able to transport their goods much more efficiently and economically,” the Michigan DOT concluded. “Recent trends and studies suggest that the federal government and other jurisdictions are beginning to recognize the validity and benefits of the approach Michigan has used for decades.”

The House Transportation and Infrastructure Committee will be marking up a surface transportation bill on October 22. Steenhoek, told DTN that, “We and other proponents of this legislation are working to ensure it gets included in the larger highway bill.”

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