If 5K's service to Fairfax City were eliminated - an alternative being considered by Metro because the city started its own independent rush-hour line - hardly any of the automobile-driving commuters would notice.

But Sandra Doty would notice. In fact, if the 5K didn't run through the city anymore, Doty's life would be turned upside down.

"I'm a working mother," Doty told a Metro hearing on Fairfax City bus service last week. "I need my income to make a living. If I lose this bus, I will lose my job."

She spelled out the conomics: The 5K costs her $20 a month. The car she would have to buy if the 5K were dropped would cost about $167.50 a month, Doty estimated. But she can't afford $167.50 a month.

The hearing, presided over by Joseph Alexander, who is the Fairfax supervisor representing Lee district as well as a Metro board member, gave bus riders one of their rare opportunities to be heard in a controversy that has usually swirled around top officials of the region - none of whom probably depend on a bus for their livelihood.

"We are a very small voice," Doty acknowledged, "but we are individuals who have needs."

Elton Bonner also rides the 5K. It is not essential to him, as it is to Doty, but he pointed out: "We (the Bonner family) can get by with one car because I can use the 5K two to three days a week."

Bonner's decision to use the 5K has three other effects, which are miniscule when measured alone but can have a sizable impact when considered with the impact that bus riders could make as a group: There is a reduction in use of gasoline; there is a reduction in traffic congestion, and there is a reduction in the bus subsidy payments that local jurisdictions have to make to keep Metro running.

In asking the Metro board not to curtail service, the testifying bus riders were critical, in varying degrees, of their Fairfax City government.

A common complaint was that the city's new independent commuter service won't help the bus riders who don't work along the line's one route, which, after making a fishhook-shaped circuit through the city, goes to the Pentagon and then to K Street NW in the District via 14th Street NW.

With the city having started its own line and refusing to make subsidy payments to Metro, the regional system's board must make a choice: Continue present Metro service in the city and have other jurisdictions - most notably Fairfax County - pick up what would be the city's subsidy bill; continue service through the city but sharply reduce boarding or departinggg locaations, or stop all bus service at the city's boundaries.

Among the bus riders asking Metro's board to keep service as it is was city resident Eugene Kennedy.

"If wee have some time to deal more effectively with locally elected officials," he said in an allusion to forthcoming council elections, "in six months, you will see a more reasonable attitude."