SF Chronicle. San Francisco’s Municipal Railway—the public transit operator in San Francisco—has missed the first of three deadlines to phase out about 150 of its highly polluting pre-1991 diesel buses. Muni’s total diesel fleet numbers 454 vehicles.

The first deadline, which expired last month, was mandated in 2004 by the voter-approved Proposition I and required Muni to replace a quarter of the buses.

The San Francisco Municipal Railway is the seventh-largest public transit system in the United States, as measured by ridership, and runs the fifth-largest bus fleet in the United States.

“We are very concerned with getting the 1988 diesel buses off the road as soon as possible,” said Linda Weiner, a spokeswoman for the American Lung Association. “These buses are so old they cannot be retrofitted with any modern technology, and in the meantime continue to spew toxic emissions of particulate matter that can lead to lung cancer and premature death.”

Muni officials said they are trying to satisfy the requirements of Prop. I, which, they note, did not provide for any funding for the new buses. The agency uses the older diesel buses only when needed as part of a reserve fleet of vehicles.

“The problem is the legislation did not come with any money,” said Muni spokeswoman Maggie Lynch. “We are trying to comply with Prop. I. Over 50 percent of our daily fleet is non-polluting,” Lynch said, referring to Muni’s full range of transit vehicles, diesel and electric trolley buses, electric trains and cable cars.

The transit agency signaled last year it was interested in buying hybrid diesel-electric vehicles after they were certified for use in California.

But last week, Lynch said Muni instead is working on a deal to buy 45 used and less polluting clean diesel buses from AC Transit for $4.1 million. Muni is expected to acquire the buses—built in 1993 but fitted with upgraded engines—within the next 60 days, she said. Muni is also looking at longer-term plans to buy hybrid diesel-electric buses.

AC Transit is the public transit operator in Alameda and Contra Costa counties, which include Oakland and part of the East Bay. AC Transit has been one of the most aggressive public transit agencies in terms of investigating new fuel efficient and less polluting technologies, including hydrogen. (Earlier post)