In a unanimous decision last month, the Supreme Court upheld the authority of the Environmental Protection Agency (EPA) to regulate clean air without considering the cost of implementing its rules. That has left many in the trucking industry worried about the long-term implications of the court's decision. "Industries that depend on transportation will feel the impact of these rulings in three to five years," predicts Allen Schaeffer, executive director of the Diesel Technology Forum, a coalition of truck-engine makers and diesel-fuel suppliers.

The American Trucking Associations (ATA) and a dozen other industry groups had challenged the EPA's standard for ozone emissions on two counts. First, they contended, the EPA failed to consider the economic impact of its regulations. The plaintiffs also argued that the EPA had usurped congressional authority and exceeded its regulatory powers in setting the ozone standard. A federal appeals court had rejected the truckers' first argument but sided with them on the second.

The nation's highest court agreed that the law did not require the EPA to consider the resulting costs—a decision that left the trucking industry disappointed. "It's a difficult pill to swallow," says Earl Eisenhart, government affairs consultant to the National Private Truck Council, which represents private fleets.

The Supreme Court did offer one consolation to the truckers: It ordered the U.S. Court of Appeals for the District of Columbia to revisit how the EPA set the new standard. If the appeals court agrees that a revision is needed, then the EPA could be forced to revise the ozone-emission standard itself. A hearing is likely before the end of the year.

The day after its victory in court, the EPA announced that it would go ahead with new rules requiring a 97-percent reduction in the sulfur content of diesel fuel by June of 2006. Engine makers, moreover, will have to phase in new products that run on cleaner diesel between 2007 and 2010. "Cleaner fuel will drive up transportation costs," the Diesel Technology Forum's Schaeffer notes. "Ninety percent of all the nation's freight moves on diesel engines, whether it's barge, rail, truck, or ocean."

No wonder, then, that many motor carriers and others in the trucking community would like Congress to consider legislation revising the Clean Air Act to include economic impact. "The ruling engenders a sense that Congress needs to review the Clean Air Act," Eisenhart says.