Researchers Outline Plans for Federal Truck Size and Weight Study

The federal government’s truck size-and-weight study began taking shape last week as researchers outlined how they plan to assess whether larger trucks affect highway safety, pavement wear and modal shifts.

Speaking on a Dec. 18 webinar, government and university researchers said the data they compile will help determine if bigger and heavier trucks can operate safely on U.S. roadways.

The study was mandated by the federal transportation law known as MAP-21.

Although the findings could encourage or disparage efforts to increase the weight limit for heavy trucks to 97,000 pounds from 80,000, researchers will not be tailoring the study to alter regulatory policy, said Tom Kearney, freight operations program manager for the Federal Highway Administration.

Kearney said researchers will look at six heavy-truck configurations, including twin 33-foot trailers weighing 80,000 pounds, triple 28-foot trailers weighing 105,500 pounds and triple 28-foot trailers weighing 129,000 pounds.

The study will use the Intermodal Transportation and Inventory Cost model tool to estimate shifts between trucks and other modes due to the introduction of the alternative configurations. The ITIC is similar to the model used in the Department of Transportation’s size-and-weight study in 2000, researchers said.

The pavement wear-and-tear portion of the study will use FHWA and American Association of State Highway and Transportation Officials models to analyze four pavement types in four climate zones with high, moderate and low truck volume.

Researchers also said they will work with the Commercial Vehicle Safety Alliance to evaluate enforcement costs and state permit and weigh-in-motion data to assess how larger trucks would affect regulatory compliance.

The study also will conduct an inventory of federal laws and regulations that could be affected by alternative configuration trucks.

Researchers said they will select 400 bridges to estimate structural impacts, maintenance costs and new load postings related to the introduction of alternative truck configurations.

To better assess safety effects, researchers will analyze crash rates based on specific routes, individual fleets and states, and use safety inspections and violations to better identify patterns.

The study also will compare crash severity and fatality rates with 5- or 6-axle trucks weighing 80,000 that operate on U.S. highways.