High-tech bus is one step toward cleaner air in L.A.

The end of the Cold War has been a boon on several fronts, not the least of which is the unleashing of American ingenuity, productivity and resources for the benefit of consumers and the environment, both of which will get more attention now that military spending has been trimmed. An advanced technology transit bus (ATTB) developed by several companies including Northrop Grumman, the Los Angeles-based military aircraft manufacturer, is a case in point.

The Los Angeles County Metropolitan Transportation Authority (MTA) was the first of several transit agencies to use the bus. MTA Chairman Larry Zarian says development of the vehicle represents a “technological milestone, a means of transportation that’s right for Los Angeles and right for the country.”

The bus prototype is equipped with a unique hybrid propulsion system in which an engine fueled with compressed natural gas powers a generator. The generator then delivers electricity to the bus’s two rear wheels. This design results in a more fuel-efficient and reliable system than that of a conventional compressed natural gas powered bus.

Additionally, weight is not a problem with the prototype, which was manufactured using advanced composite technology developed by the Dow Chemical Co., Midland, Mich. It weighs about 11 tons – roughly 4 1/2 tons less than a conventional compressed natural gas bus.

And, since the extreme weight of steel panels used on conventional buses is chiefly responsible for two of the largest expenses in transit maintenance – excessive wear on the brakes and decreased fuel efficiency – the bus’s lighter weight means much lower operational expenses. The light weight is attributable to the material as well as parts consolidation allowed by the use of composite materials, says Dave DeMent, manager of ATTB project development for the aircraft manufacturer.

While a conventional bus structure may contain hundreds or thousands of parts, the basic structure of the composite bus consists of only four parts. Its developers say the prototype has performed well in testing for impact resistance, weatherability and corrosion resistance – all crucial in the rugged city transit environment. The prototype also boasts a gelcoat containing a special resin blend that is resistant to graffiti.

The bus’s composite structures have an anticipated service life of 25 years – significantly longer than conventional diesel bus structures, which average 12 years. “Every transit agency would like to reduce the lifecycle costs of its buses,” says Tim McCarthy, market development manager for the composite manufacturer. “The composite bus has the potential to provide the public with a more efficient transportation system well into the next century.”

The MTA also has changes in store for its diesel bus fleet. Through a muffler retrofit program affecting 1,350 diesel buses, the agency hopes to reduce by more than 600,000 pounds per year the amount of pollutants emitted.

In a joint program involving the MTA and Iselin, N.J.-based Engelhard Corp., a manufacturer of various environmental technologies and specialty chemical products, the buses will be refit with the company’s CMX catalytic converter muffler. The converter-muffler system is EPA-certified to reduce hydrocarbons by 50 percent, carbon monoxide by 40 percent and total particulate emissions by a minimum of 25 percent.

The technology was the first to be approved by the EPA under its urban bus emissions regulation for engine retrofit/rebuilds, which affects cities with populations over 750,000. About half of the converter mufflers had been installed on buses across the country by mid-November.