In the car-oriented subdivisions of Fairfax County, Metrobus, for a long time, was only slightly more popular than crabgrass. When each commuter could be king of the road inside his carpeted and air-conditioned coach, why would he place himself at the mercy of one of those dirty, smoke-belching dented aluminum specters that so often clouded the view from his windshield in the morning and evening rush hours.

But Metro is coming to those distant subdivisions. Saratoga, just above Lorton Reformatory in southern Fairfax, got three Metro commuter buses in April, and because they are carrying standing-room-only loads, the community may soon get a fourth bus. Great Falls, where Mercedes-Benzes are considered a sensible way to take to the road, got two buses in August, and three fringe parking areas.

The most recent example of this phenomenon is Burke Centre, the new town below Fairfax City, where Metro inaugurated bus service Monday with five runs carrying more than 200 passengers.

When the buses -- quite clean, by the way -- rolled in, the passengers, who apparently survived the round-trip experience with their dignity intact, were treated to wine and hors d'oeuvres at the Visitors Center. (In Saratoga and Great Falls, commuters were sent off on the first day with a glass of champagne -- apparently to cushion the blow of transportation shock.)

At Burke Centre, the first person off the first returning bus was Larry Tanner, one of the community leaders who helped bring Metro to such a distant outpost. With pride in his voice, he said, "This is a big day for Burke Centre. We're now part of the metropolitan area."

He might also have said that Metro was now part of the far reaches of Fairfax, and that is a significant event, too.

With Metro developing a constituency throughout Fairfax, even where the car has hitherto been the vehicle of choice, the bus-operation deficits are not so likely to be a divisive political issue, stunting the extension of mass transit, as has happened in the past. In fiscal 1980, Fairfax's share of the deficit from bus operations is expected to be $11.9 million, double what it was four years ago. The five buses serving Burke Centre, even if they run full, will contribute about $100,000 to that deficit.

Fairfax Supervisor Marie V. Travesky, who serves both the Burke Centre and Saratoga areas, is a Republican, but she sees no fiscal inconsistency in supporting an operation that loses money even when it is successful. Bus service, even at a loss, can be fiscally sound, she says, if it forestalls the need for expensive road improvements.

But politicians wouldn't be voting for deficits in these cost-conscious times if something remarkable hadn't been taking place among their constituents. How did the buses, once resolutely ignored, win friends in suburbia?

The first answer that comes to mind is the Great Gasoline Crisis. But the residents of Saratoga were clamoring for bus service long before the first gas line formed even in California. What turned them around, according to Travesky, was not the gas crisis but the congestion crisis and, in the case of young families, a financial question involving far more than the price of gasoline.

Travesky said many of her constituents were tired of the stop-and-start trip up Shirley Highway, an experience that could make the Santa Monica Freeway seem like the Yellow Brick Road. Others, the younger ones, heavily saddled with a mortgage, were looking for a way to avoid buying a second car -- a purchase that can take a $400-a-month bite out of the budget.

Dissatisfied with the vicissitudes of car pools, when they would be formed at all, residents opted for the only alternative left -- buses.

Ordinarily, Metro would be reluctant to extend service to distant points like Saratoga or Burke Centre. But community groups in those areas did some thorough canvassing and were able to offer convincing evidence that the ridership was there. Furthermore, the Fairfax Board of Supervisors voted to start picking up the deficit immediately. There wasn't going to be any pretending that maybe the service would pay for itself. It can't and won't, everyone now seems to agree.

If the examples of Saratoga and Burke Centre continue to be successful (the Great Falls runs are proving shaky, apparently largely because a bridge repair has forced a time-consuming detour), no doubt other neighborhoods will want Metrobus signs posted on their roads.

But when Metro's problem is trying to satisfy the demands of a generation that grew up in a car -- well, that problem can't get acute enough.