Federal regulations are forcing truck manufacturers to manufacture cleaner vehicles, but there's a hitch. In reducing particulate emissions from diesel truck engines, they've also reduced fuel economy -- and trucking firms are not too happy about it, according to this story in the Wall Street Journal (for subscribers)

Previous-generation trucks average about nine or 10 miles to each gallon of diesel fuel. New engines designed to meet the more-stringent federal mandate on truck exhaust get about one mile less to the gallon. That may not seem like much, but it all adds up for large fleet owners that operate trucks crisscrossing the country.

"For every additional mile-per-gallon lost, it costs us about $10 million in [total annual] fuel costs" said YRC Worldwide Chief Executive Bill Zollars. YRC is one of the largest transportation providers in the country, operating a fleet of 20,000 trucks.

The story also notes that new truck sales spiked before the new requirements took effect.

Emission-fuel economy trade-offs are not unique to trucks -- or even to vehicles. Pollution controls often result in energy efficiency losses (though not in the case of carbon dioxide emissions). This does not mean we should not try and reduce diesel particulate emissions, or other emissions for that matter, but it is a useful reminder that there trade-offs are ubiquitous in environmental policy, as they are everywhere else.