Facing tougher air pollution requirements, cities are turning increasingly to buses powered by natural gas, although 93 percent of the nation''s 50,000 transit buses still run on diesel, according to a new study.
The study by INFORM, a national environmental non-profit research organization, concluded that the growing acceptance of cleaner-burning natural gas as fuel for transit systems represents "a major shift" by the transportation sector to reduce air pollution.
The number of natural gas buses (both compressed natural gas and liquefied natural gas) in operation in the United States has grown from 100 in 1992 to 3,204 in 1999 -- and is expected to grow to nearly 5,000 buses when pending orders are filled.
Between 1993 and 1999, the number of diesel buses operating in the United States actually declined, according to the American Public Transit Association (APTA). Nevertheless, diesel is still the predominant fuel used by transit operators, accounting for about 93 percent of bus fleets.
"In the next decade, more than $10 billion in public funds will be spent to purchase more than 75,000 new buses," said Joanna Underwood, president of INFORM. "The decisions that public transit systems make when purchasing buses will have a major impact on the of our nation."
"More than 100 million Americans, including 35 million children are breathing air that fails to meet federal air quality standards -- diesel buses are a major reason why," she continued. "Their exhaust contains lung-clogging fine particulates and more than 40 toxic air contaminants known or suspected to cause cancer."
Natural gas runs 20 percent of the bus fleets in 31 cities from Boise, Idaho and Bakersfield, Calif., to Tacoma, Wash., and Phoenix.
A number of cities, including transit authorities in Atlanta, Los Angeles and Sacramento, Calif., have said they no longer will purchase diesel buses, according to the study.
EPA has already released the first phase of a two-part strategy to reduce diesel emissions from heavy-duty trucks and buses by 95 percent by 2006.
The prospects of cleaner burning diesel-powered buses and the higher cost of natural gas-powered buses is keeping some transit agencies from making a shift from diesel to natural gas, the report acknowledged.
Natural gas-run buses cost 15 to 25 percent more than those using diesel fuel. Transit agencies must also face the cost of building new refueling and depot facilities, which can cost from $1 million, and possibly higher operating costs.
These costs should be "weighed against the cost of vehicle-related air pollution and its effects on human health," the report said.
by Virginia Sutcliffe