Panel OKs Diesel Bus Trade-Off

California’s air quality board Thursday left intact a stringent smog-fighting standard for new buses but will allow transit agencies to keep buying more highly polluting diesel buses as long as they compensate by retrofitting some old ones.

Because no diesel engines will be able to comply with an emission standard scheduled to go into effect in 2007, the Air Resources Board considered easing the standard to allow new diesel buses to emit six times more nitrogen oxides until technology improves in 2010.

But in a unanimous vote after six hours of debate and public testimony, the board decided that relaxing the standard would be the wrong message to send transit agencies.

California has about 10,000 transit buses, with about 60% of them diesel-powered, and they are among the state’s largest sources of smog and soot.

The state requirement for new buses will remain the same as when it was adopted in 2000. But, board spokesman Jerry Martin said, “the board had to provide some remedy for the transit agencies with the older diesel buses.”

The board members decided that transit agencies could buy buses that exceed the standard, but only if they offset the extra emissions by putting smog-control devices on some of their older diesels. If the board had not granted such an exemption, about 40 California transit agencies that rely on diesel buses, largely in Northern California, would not have been allowed to buy any new ones for three years.

Environmentalists and diesel transit agencies supported the decision.

Buses powered by natural gas can meet the new standard in 2007, but diesel technology has not advanced quickly enough.

Most agencies in the Los Angeles Basin operate buses powered by cleaner-burning alternative fuels, mostly compressed natural gas. But most other transit agencies in the state have decided against alternative fuels because building fueling stations costs millions of dollars.