King County is to purchase of up to 500 new buses that will help deliver one of the biggest bus service expansions in Metro history.

Most of the buses will be articulated hybrids manufactured under a contract believed to be the largest of its kind in North America.

Metro selected New Flyer Industries, General Motors Corp. and Cummins Engine Co. as the major commercial partners in delivering the next generation of buses.

All the buses will meet or exceed the latest federal environmental standards. The first 22 articulated hybrids are scheduled to arrive next spring, with another planned order of 100 buses in 2009 to provide new Rapid Ride service on five routes. One of the routes will serve West Seattle. The contract will allow Metro to place multiple bus orders over the next five years to support its Transit Now initiative that expands service up to 20 percent.

The expanded and more frequent service is designed to make transit more attractive to drivers. Metro's goal is to get up to 50,000 drivers out of their cars and riding buses by 2016.