SEATTLE – King County Metro Transit in Washington will order up to 500 hybrid buses in the next five years, adding those to its 237 hybrids already on the street, according to the Seattle Times. The diesel-electric hybrids will be purchased mainly with federal grants, combined with a local sales tax increase approved by voters last fall. The ballot measure, known as “Transit Now,” will fund more frequent bus service throughout the county.

An initial shipment of 22 hybrid buses will arrive next year. They cost $719,000 each.

The purchase of up to 500 buses could cost as much as $400 million, depending on inflation and the types of buses the county orders. A batch of 100 buses would come in 2009, when Metro launches a new bus rapid-transit service for Ballard, West Seattle, Shoreline, the Redmond-Overlake-Bellevue corridor, and suburbs south of Seattle-Tacoma International Airport. The 2009 buses will have three doors instead of the normal two and a larger entryway up-front. Future orders would include some shorter, 40-foot buses.

Last year Metro operated more than 1,400 buses: 1,035 diesel buses using 20-percent plant-based fuels; 237 hybrids, which also use biodiesel; and 159 electric buses powered by overhead wires. Tests by the U.S. Department of Energy showed that a King County hybrid used 30-percent less fuel than a diesel bus in laboratory simulations. In real Seattle traffic, fuel savings averaged 27 percent, the federal study said.