King County, Washington was awarded a contract for the purchase of up to 500 articulated buses, most of which will be powered by General Motors' 2-mode hybrid system, IndustryWeek reports. The five-year contract, which could be worth as much as $400 million, is between King County and bus-manufacturer New Flyer Industries. General Motors supplies New Flyer with the hybrid system for the buses. King County has been operating a fleet of 214 GM hybrid-powered buses since 2004 and with the addition of this contract, King County could have a total of 714 buses, making it the largest fleet of hybrid-articulated buses in history. A NREL one- year comparative study (PDF) between conventional diesel buses and GM hybrid-powered buses operating on a typical King County drive cycle showed that the GM-hybrid powered buses achieved 30 percent higher fuel economy on average when compared to the conventional diesel buses and total operating costs were lowered by 15 percent.