Kenworth Truck Company’s medium-duty, hybrid-electric truck for utility operations is now in service in King County, Wash.Located in the greater Seattle metropolitan area, King County covers more than 2,100 square miles and is the nation’s 13th most populous county. The King County Department of Transportation, which became the first government agency to place the new Kenworth hybrid into service, uses its new Kenworth Class 7 hybrid to maintain traffic signals. The hybrid is equipped with a utility bucket atop a 50-foot boom, which is longer than a standard aerial lift. While a non-hybrid utility truck must idle to operate its lift, the hybrid’s lift typically operates on electric power, which reduces emissions. “We’ve logged a little over 5,000 miles as of the first of this year and the Kenworth hybrid has already achieved a 25 percent reduction in fuel consumption over a comparably equipped conventional model,” said King County Fleet Administration Division Director Windell Mitchell, who expects to attain a 30 percent or more improvement in fuel economy as the truck is further broken in by the county. The need to refuel less often allows crews to remain in the field for longer time periods, which is especially important when 12-hours shifts are required during storms and other emergencies. The county uses B-20 biodiesel as its fuel. The blend provides additional reductions in greenhouse gas emissions.Kenworth’s medium-duty hybrid, which can carry a payload of up to 16,000 pounds, features an integral transmission-mounted motor/generator, frame-mounted 340-volt battery, and dedicated power management system. Above 30 mph, the Kenworth hybrid operates like a standard diesel vehicle with all power coming from the engine during steady driving conditions. Below 30 mph, it uses a combination of diesel and electricity with the system automatically switching between the two modes of operation. Electricity generated through regenerative braking is stored and used for acceleration, assisting the diesel engine.