It’s been two decades since Congress seized from states the authority to regulate the size of the biggest trucks traveling the highways. But what started as a temporary “freeze” on state rule-making predictably turned into a permanent federal usurpation of state regulation.

The now-petrified standards have been rendered largely obsolete by advances in engineering, thus inhibiting productivity improvements for hauling freight. It’s time, therefore, for Washington to get out of the way.

The freeze on truck “configurations” came with passage of the Intermodal Surface Transportation Efficiency Act of 1991, which consolidated federal power over the nation’s highway network (read: micromanagement). Proponents argued for standardizing the differing state rules governing “longer combination vehicles” (LCVs), which consist of a truck tractor and two or more trailers or semitrailers with a gross weight over 80,000 pounds and an overall length of one or both cargo units exceeding 28.5 feet. Railroads, too, had an interest in limiting trucking volume.

Rather than harmonize the standards, however, Congress simply prohibited states from changing the routes or weight and length limits on LCVs that were in effect on June 1, 1991. And there they have remained ever since, despite major advances in transportation technology and safety.

A patchwork of state standards can prove challenging for interstate trucking. But at least states have shown relative flexibility compared to the regulatory immobility of the feds. If LCV regulations are deemed necessary, state regulators are in a far better position to determine feasible standards based on local conditions and to be held accountable for screwing up.

That’s not to say that state LCV standards are necessarily rational. Truck size has long been a contentious issue, with truckers, railroads, environmentalists, and safety activists all competing for regulatory favor. According to researchers at Iowa State University’s Center for Transportation Research and Education:

Prior size and weight regulation promulgated by states was based on political considerations and is a result of compromise among a number of constituent parties.… These compromises were not necessarily based on safety concerns of the roadway environment, engineering concerns of the roadway infrastructure, and economic concerns of an efficient motor freight industry.

There is a better way. The manifold variations in LCV configuration call for “performance-based” standards. That is, standards set according to vehicle design and handling properties. For example, vehicles with better brake performance and/or suspensions could safely handle heavier loads. The adoption of performance-based standards would introduce a modicum of rationality into trucking regulation and help to mitigate variations among states’ standards.

More sensible standards promise economic benefit. Fewer trucks are needed if size limitations are eased, for example. Indeed, some advocates estimate a productivity increase of 30 percent or more from more sensible regulation.

Whatever benefits claimed for federal regulation of LCVs have been entirely negated by Washington’s failure to deliver in the past 20 years. The Obama Administration has recently embraced regulatory reform as a means of economic growth. Ending the federal freeze on state regulation of LCVs offers an opportunity to deliver on that goal.