Alarmed by the soaring cost of the region's Metro system, Fairfax County will study the feasibility of establishing an independent local bus service in Northern Virginia, county board chairman John F. Herrity Jr. said yesterday.

Herrity said mass transportation experts will be hired to study the nuts and bolts of having locally owned buses provide cross-county service for the sharply growing number of people who both live and work in Fairfax.

In addition, Herrity said the county buses might provide shuttle service to suburban Metro rail stations for commuter trips into Washington.

"The Metro bus operation is becoming far too expensive," Herrity told a conference on Metro sponsored by the Fairfax Federation of Citizens Associations. We have to take a serious look at an independent alternative." a

Metro general manager Richard S. Page, who also took part in the conference, indicated that he would not oppose a possible move by Fairfax to set up a separate bus system. "I'm not going to advocate that," he said. "If you want to do it, that's your decision."

In an interview later, Page said he doubted that the localities taking part in Metro could make any substantial savings by operating separate bus systems on their own.

The main factors setting costs, he said, are the rules accompanying federal aid -- which pays up to 80 percent of most costs -- for buying buses and unionized drivers for operating them. Page said he couldn't see any "serious bus system" getting by for long without federal aid or unions.

Metro itself, Page said, now is "serious about controlling costs" through new budgeting techniques, computerized scheduling, and a plan to experiment with cheaper deisel fuel. He said Metro is seeking major changes in its union contract, which expires April 30.

For the past four years Montgomery County has operated its own Ride-On bus service which connects to Metro routes. Fairfax City has hired its own commuter buses.

Recently, both Arlington and Prince George's counties began preliminary studies of alternatives to Metro bus service.

Herrity said the Fairfax board ordered a staff analysis of an independent bus system last summer and now the county is moving to more detailed planning by bus experts.

Since 1977 the total government subsidy for Metro bus service has risen from $55.8 million to $94.7 million this year. It is expected to rise another $15 million in 1981.

According to Metro's budget, each passenger trip in 1977 cost taxpayers 44 cents in addition to the fare that was paid. Despite fare increases, the subsidy is expected to reach 72 cents per trip this year.

The prime reason for the increase is labor costs which account for 85 percent of bus operating expenses.

Effective today, Page said, the pay for an experienced bus driver rises to $9.86 per hour, reflecting an automatic 26-cent cost-of-living increase required under the transit worker's contract.

The annual pay for drivers now is $20,508, and their fringe benefits cost Metro about one-third more, Page said.

Fairfax school buses now carry more people than Metro within the county, Herrity said, and do so at 30 percent of the cost, using many housewives as part-time drivers.

When someone in the audience shouted, "Can you recruit housewives to drive Metro buses?" Herrity retorted; "Why not"

Despite his doubts about Metro's bus service, Herrity said he strongly favors completion of the 101-mile Metro rail system to be the "backbone" of public transit for the area.