The Fairfax County Board of Supervisors has approved a controversial $300 million commercial office park near Herndon that critics say will generate a "horrendous" amount of traffic in the already congested western part of the county.

The supervisors voted 5 to 1 Monday to rezone the 94-acre property along Centreville Road, north of the Dulles Airport Access Road and south of Herndon's boundary, from residential to light- and medium-industrial use. County planners said earlier they were worried about an expected increase in traffic around the site, but Herndon officials and nearby residents were satisfied with the developers' plan to widen two-lane Centreville Road to six lanes.

Supervisor Audrey Moore (D-Annandale) said she voted against the project because the development would cause "a pretty horrendous" traffic problem. Supervisor Joseph Alexander (D-Lee) and Board Chairman John F. Herrity abstained; Supervisor T. Farrell Egge (R-Mount Vernon) was not in the room at the time of the vote.

The development, called Worldgate Office Park Inc., will be nearly 3 million square feet and consist of two hotels, a health club, restaurants, offices and shops. New York developer Michael Swerdlow and the Charles E. Smith Co. said the road construction will start immediately. They said the project will take at least eight years to complete.

It took county planners and the developers almost a year of negotiations and 21 plan revisions before Supervisor Nancy K. Falck (R-Dranesville) would support the development. The county's planning commission earlier recommended denial of the project, saying the development would be too intense for the area.

Falck previously had agreed that the development would generate too much traffic for rural Centreville Road and nearby Monroe Street, but agreed to support the application after Swerdlow promised to widen the two streets before construction of the office park started. That way, county planners said, traffic congestion might be eased before the office park's buildings are occupied.

Swerdlow also promised to provide 120 feet of trees and shrub as a buffer between the office park and a group of residences that borders the property. The developer also agreed to pay for additional road construction after the project is completed if state and county highway officials decide more improvements are needed to handle the traffic.

Usually, the state pays for additional road improvements beyond those promised by the developer when the project is approved.

The Worldgate site is part of a proposed land swap between the Town of Herndon and Fairfax County. If the Worldgate property is transferred to Herndon, the office park is expected to produce about $500,000 a year in tax revenue for the town. The land swap plan is still being considered by board members.