The Department of Transportation's Federal Highway Administration (FHWA) failed to assess the impact of increased truck size and weight limits on the cost, condition, and safety of the nation's highways even though it had enough data to do so, a committee of the Transportation Research Board (TRB), part of the National Academy of Sciences, said today.

In its report, the TRB committee acknowledged that the DOT subagency did not have optimal data sets to work with. However, a "more comprehensive and useful response would have been possible" even with the information FHWA had at hand, the 13-person panel concluded.

The panel said that DOT failed to estimate expected bridge structural costs, frequency of crashes, and infrastructure costs on certain roads, even though they had sufficient data to make a case.

As part of the 2012 transport funding law, Congress mandated DOT to conduct a study into the effect of raising the weight and length ceilings of trucks on U.S. infrastructure, and report back to lawmakers within three years. DOT then engaged the TRB to review the FHWA's findings. In June, DOT told Congress that no change should be made to current truck size and weight laws because the agency lacks the necessary data to make accurate assessments of the national impact of any adjustments.

Peter M. Rogoff, undersecretary for policy, said at the time there wasn't enough data available from crash-reporting statistics to determine a vehicle's weight at the time of an accident; DOT could not determine by the available data whether trucks, prior to a crash, were fully loaded, running overweight, at legal capacity for their axle configurations, or had unevenly distributed weight, Rogoff said.

In a statement today, FHWA said it is "reviewing the results of the (TRB) peer-review report and will be incorporating information from the report into our final MAP-21 Comprehensive Truck Size and Weight Study Report to Congress."

The length and weight of heavy-duty trucks operating on the federal-aid highway system, which includes the 44,000-mile Interstate Highway System, is fixed at 1982 levels. Six states, mostly in New England, allow trucks with a gross vehicle weight (tractor, trailer, and cargo) of more than 80,000 pounds—the current national limit—on their portions of the federal aid system as long as each is equipped with a sixth axle. In addition, there are 19 states that allow twin-trailers of more than 28 feet each—the current limit—on their parts of the federal network. Language included in the fiscal-year 2016 DOT appropriations bill would open federal-aid highways to 33-foot twin trailers.

In a phone interview, James Winebrake, dean of the College of Liberal Arts at Rochester Institute of Technology and chair of the TRB panel, said FHWA could have done a better job of "framing the question" and delivering an adequate assessment with the available data. Instead, the agencies said nothing, he added.

Winebrake said the committee was mindful that DOT and FHWA worked under data constraints. In its report, the panel urged Congress to provide needed resources to the agency to conduct a more robust analysis.