The city of London has just taken delivery on the first a new strain of hybrid diesel-electric double-decker buses that mark the dawn of a new era in the history of these iconic mass transporters. The buses, built by Britain's Alexander Dennis Limited (ADL), are fitted with a well-proven HybriDrive package from BAE Systems, which has supplied similar motivation for over 1,500 buses currently operating in cleaner, greener fleets in Houston, New York, San Francisco, Toronto and Ottawa. According to BAE estimates, HybriDrive propulsion systems have saved five million gallons of diesel fuel to date and prevented more than 50,000 tons of CO2 emissions.
BAE's HybriDrive package consists of a diesel engine with about half the displacement of a conventional bus unit that drives a generator which, in turn, feeds power to an electric motor. A lithium-ion battery pack adds extra muscle when needed for acceleration, and can be replenished by the engine as well as by the vehicle's high-efficiency regenerative braking system. A sophisticated controller setup eliminates the need for a conventional transmission, and this latest iteration of HybriDrive also benefits from a smaller, lighter and longer-lasting battery pack designed to further lower operating costs.
"Our hybrid technology is the most proven in the industry, with more than 70 million miles of revenue service to date," noted Rob Lindsey, BAE Systems director of transport systems for the U.K. and Europe. "Joining with Alexander Dennis brings the combined benefits of improved fuel economy, lower production of greenhouse gases and other emissions, and reduced vehicle maintenance to the transit system and to the residents of London." Ultimately, the City of London will have 17 of these new hybrid buses in the evaluation fleet serving its greater metro area.