Independent Review of DOT Size and Weight Study Backs Original Researchers

An independent scientific review of the Department of Transportation’s truck size-and-weight study largely agreed with original researchers that weaknesses in some of their research models and data hampered meaningful conclusions.

The review by a special committee of the National Academies of Sciences, Engineering and Medicine also concluded that the congressionally mandated study was not responsive to some of the questions Congress posed.

“The study does not respond to the legislative charge to evaluate the safety impacts of changing regulations to allow alternative configurations,” said the report published Oct. 8.

DOT’s $2.3 million study (by the Federal Highway Administration arm of the agency) analyzed the effects of larger truck configurations and higher weight limits on highway safety, cost, bridge and road degradation, and enforcement. Ultimately, it seemed to raise more questions than answers, DOT acknowledged.

When the study was released in June, DOT Under Secretary Peter Rogoff sent a letter to congressional leaders indicating that the research “revealed very significant data limitations that severely hampered the Federal Highway Administration’s efforts to conclusively study the effects of the size and weight of various truck configurations.”

“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,” Rogoff wrote in a June 5 letter. “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.”

The review committee said, however, that useful responses were possible. It identified assumptions and simplifications in the study that “might result in misleading estimates of infrastructure, traffic, and safety impacts.”

For example, the committee said that Congress specifically required that the study compare impacts with the infrastructure in each state of vehicles with axle and weight limits in excess of the federal law and regulations to those vehicles that do not operate in excess of regulations.

“The pavement analysis in the DOT study does not adequately address this part of the charge,” the committee said.