Smelly, particle-laden diesel fumes from trucks and buses are the bane of highways and city streets. But they'll soon grow much thinner, thanks to a decision by a federal appellate court and the determination of the Bush administration, which is firmly on the green side of this clean-air issue.
On May 3, a three-judge panel unanimously upheld rules issued by the Environmental Protection Agency that require a 95 percent reduction by 2007 in the pollution caused by diesel engines. The rules also demand the removal of nearly all soot-producing sulfur from diesel fuel by 2006.
The plaintiffs in the case, refiners of diesel fuel and engine manufacturers, claimed the rules impose unreasonably short deadlines. The court wisely disagreed.
This ruling may be appealed, but it should stand, because of implications that go far beyond better air. Long-range benefits include better overall vehicle mileage and air quality. That's because the sulfur-free requirement will stimulate the marketing of diesel-powered cars and light trucks capable of meeting stricter emission standards. Sulfur in the fuel creates particles that clog exhaust filters.
Since diesel-powered vehicles generally get better mileage than their gasoline counterparts, carmakers believe the new diesel rules will help them meet tighter fuel-efficiency standards down the road as well.
Then there's the politics of this issue. The rules will give the Bush administration added mileage on its bumpy environmental-policy road. The Bush EPA was firmly aligned with environmentalists on this one. It was also aligned with its predecessor, since the rules were issued in the final days of the Clinton administration. It didn't hurt, no doubt, that big industrial interests like Detroit also supported the rules.
But another party that's usually in the Bush corner may not be so happy. That's Mexico, whose trucks have been promised freer access to the US. Currently, Mexican truckers can only go 20 miles over the border before being sent home. If that restriction is pushed aside this summer, as the president plans, the Mexicans may soon find themselves driving into a regulatory barrier that some won't be able to clear. Many Mexican trucks are older and more pollution-prone.
So there's sorting out to come, not only inspection programs for Mexican trucks, but rapid development in the US of techniques to clean up diesel engines and to purify diesel fuel.
But the payoff in cleaner, better-smelling air should be well worth it.