Fairfax County will significantly expand its Fairfax Connector bus service starting tomorrow in the Reston, Herndon, Tysons Corner and West Falls Church areas, more than doubling the number of trips on both weekdays and weekends.

Officials said the increased service is intended to complement a more ambitious federally financed plan to eventually introduce express bus service along the Dulles Access Road, which would in turn be a first step toward extending rail service in the 22-mile corridor.

The operations debuting tomorrow include expanded service during rush hours, middays and evenings as well as express buses to Tysons Corner and the West Falls Church Metro station from Reston and Herndon. The program also increases the number of so-called reverse commute buses, which run in the opposite direction of traditional rush-hour traffic, and routes in areas previously unserved by transit.

In adopting a new routing plan based on transit hubs and spokes, the county plans to boost weekday bus trips in the areas by 119 percent and weekend bus trips by 111 percent, officials said.

New service for western Fairfax County will be run primarily through the new Herndon-Monroe park-and-ride lot opening tomorrow at Sunrise Valley and Roark drives. Connections will be available at the lot to other routes in Herndon, Reston and Tysons Corner as well as in rapidly developing Dulles Corner.

"Dulles Corner is experiencing tremendous commercial development, so there are increased transportation demands from employers in the area," said Andy Szakos, chief of transit operations for Fairfax County. "We believe the new service in western Fairfax will help companies attract and retain employees."

The Herndon-Monroe lot has spaces for 1,745 cars, and officials hope it will become a staging point for car-pooling on the Dulles Toll Road.

The proposal for bus rapid transit along the Dulles Access Road, which involves express buses making limited stops at railway-like stations that can later be converted for train use, received $86 million from Congress last year for design and preliminary development. The initiative has been named one of 10 federal demonstration projects in bus rapid transit in the United States.