Diesel Buses Are ‘On Their Last Gasp’

Soot-belching buses seem as symbolic of city life as crime and traffic. But gradually, they are vanishing from America’s streets.

Cleaner-burning natural gas has become so popular with transit agencies that experts predict diesel buses will be virtually eliminated within a dozen years in many urban areas, especially smoggy Southern California. One of every five new buses ordered in the United States is powered by alternative fuels.

Diesel buses are “on their last gasp,” said Rick Hittinger, a general manager at the Los Angeles-based Metropolitan Transportation Authority, which operates the world’s largest fleet of alternative fuel buses.

Replacing diesel in trucks is a problem in part because of the lack of fueling stations that sell alternative fuels, such as natural gas. But urban buses return home to a central spot to fuel and stay within a local area, making them ideal for new technologies.

Of the 2,100-bus fleet in Los Angeles, 591 are fueled by compressed natural gas, or CNG, which puts out about half the carcinogenic particles and smog-forming gases of a brand-new diesel bus. The MTA has ordered 764 more, which are expected to arrive within two years.

In Orange County, 40% of the fleet will be liquefied natural gas by 2001, and the goal is to get rid of all diesels by 2010.

The transition, however, “is not cheap and it’s not easy,” Hittinger said.

In 1993, Houston’s Metropolitan Transit Authority was the first to try liquefied natural gas (LNG) buses. Unfortunately, the engines had serious defects--the gas valves stuck, so the cylinders burned out.

It was a painful lesson about the cost of being a pioneer of new technologies. Recent models have been vastly improved, and the agency recently purchased more, said Richard Rotenberry, supervisor of alternative fuels for the Houston agency.

In Los Angeles, the MTA also learned the hard way about experimenting with buses. It tried methanol, but such severe mechanical defects developed that the buses had to be pulled off the road and replaced with diesels.

The new CNG engines are much more reliable than methanol, but more high maintenance than diesels, MTA officials said.

The price tag for natural gas buses also remains a big obstacle: at around $330,000 each, they cost $30,000 to $50,000 more than a diesel. The fuel is more expensive too, and requires building new fueling stations that can cost millions of dollars. Much of the extra cost, however, is subsidized by state and local funds set aside for smog control. Other types of buses are being tried, including ones that run on a combination of electricity and diesel. But the most impressive ones emit no pollution at all. Three experimental fuel cell buses, made by Ballard Power Systems, are serving passengers in Chicago. At $1.5 million each, however, they may not be practical for years.