Every weekday a little white bus shuttles around Bethesda's traffic-clogged, parking-scarce downtown area, and most of the time it's empty, except for the driver.

Montgomery County transportation officials are puzzled about the unpopularity of the four-month-old BethesdaBus shuttle, which travels every 10 minutes along a two-mile route, making 20 stops throughout the downtown area for 25 cents a ride.

Two out of every three BethesdaBus runs have no riders, said Genevieve Leary, assistant chief of the county division of transit services.

"I'd be lucky to carry six to eight people" in a day, said Harry Kennedy, who has been driving one of the service's two 15-passenger, wheelchair lift-equipped buses since August.

Last Friday Kennedy dutifully made two more riderless trips through Bethesda's heavy noontime traffic. The lonely rides "don't bother me," he said.

The seemingly worthwhile service is not yet justifying its annual $80,000 price tag, but officials said it is too early to write off BethesdaBus.

The few BethesdaBus passengers now see mostly a town in transition -- five high-rises under construction, with seven more to come, as well as a number of vacant stores -- as the bus follows its route along Wisconsin Avenue south to Bradley Boulevard and north to Battery Lane.

The county's continuing full-scale transformation of a quiet, compact downtown Bethesda to an upscale urban center -- a future Emerald City complete with streetscaping -- is several years away from completion. The office and residential towers, containing about 3.1 million square feet of space, are expected to be finished during the next few years, drawing 15,000 new employes and countless visitors to the area.

But about two blocks west of Wisconsin Avenue, the bustling Arlington Road area, with several automobile-choked shopping centers, Giant and Safeway stores, a large county library and a small well-used park, is not included in the BethesdaBus route. A county transportation official said the route "could only go so far."

"We're kind of in between things now," said Edward Daniel, chief of the Division of Transit Services, explaining that Bethesda's future stores, offices and all-day parking garages will feed shoppers and workers to the shuttle service.

Daniel said he is banking on BethesdaBus gaining some advertising when all bus routes in the western half of the county are realigned and expanded Jan. 28 to support the completed Metrorail Red Line. Countywide bus maps and schedules, which currently do not list BethesdaBus, will include the shuttle service route later this month.

The 20 stops along the route are situated at regular Metro and Ride-On bus stops, where a small red BethesdaBus sign hangs beneath the other bus signs.

Daniel said fliers on the BethesdaBus service were distributed to local businesses and at the opening of the Bethesda Metro station in August.

Last Friday at the Bethesda Metro Center -- starting point of the service -- a person wanting to ride the shuttle could distinguish the BethesdaBus from other buses congregating there only by questioning a bus driver. The BethesdaBus was white with "Montgomery County Government" painted in blue letters on its side.

Daniel said the shuttle bus should have had a magnetized red BethesdaBus sign on its side and that he did not know why the sign was missing.

Daniel said the system's objectives, besides transporting lunch- hour office workers to restaurants on the edges of the business district, include dispersing Metrorail riders throughout the downtown area and to the hotels along the northern and southern edges of Bethesda.

In explaining the lack of ridership, Daniel said the county "overestimated the demand for movement" in the area. He said people going three or four blocks are walking the distance.

Driver Kennedy said his few riders are the elderly, who "love the bus." The route includes Waverly House, a residence for the elderly, and two large apartment and town house areas at Battery Lane and Bradley Boulevard.

The system's annual $80,000 funding -- which pays for drivers' salaries, fuel and maintenance -- comes from meter proceeds in county parking lots.

The shuttle service operates Monday through Friday from 10 a.m. to 4 p.m. The smaller, lighter weight buses also will be used starting Jan. 28 during morning and evening rush hours in the Cabin John area. They will travel on MacArthur Boulevard where full-size buses are prohibited because a water conduit is located under the road, Daniel said.