The Metro Board restored the dollar bill to acceptability yesterday as it adopted a record $271 million operating budget for the year beginning July 1.

Metro had planned as recently as two weeks ago to ban dollar bills from bus fare boxes, but a concerted campaign by Fairfax County Board members Marie Travesky and Joseph Alexander turned the board around on the issue. It costs Metro about $180,000 annually to unfold, sort and count the dollar bills, which are convenient for the thousands of Fairfax County Metro riders to use since their morning bus fare exceed $1.

The budget as finally adopted after seven months of hearings and anguish is only $5 million less than the one originally proposed by Metro General Manager Richard S. Page.

Further, the budget assumes a couple of things that might not happen, including a 6 percent cap on pay increases for Metro's unionized transit workers. Those 4,800 employes, who drive buses, operate trains, man station kiosks and work on bus and train equipment, are in negotiations with Metro for a new labor contract to replace one that expires April 30. Existing practice raises their pay point-for-point with the cost-of-living index for the Washington area, and that is running at about 18 percent annually.

Another unknown is the amount of revenue that will be raised through fare increases schedule June 29. The board started its discussions on which of many various fare increase proposals to adopt yesterday, but is still several meetings away from a consensus.

The total local subsidy for the bus and rail system under the approved budget will be $107.4 million.

The budget passed the board on a 5-to-1 vote, with Arlington County Board member Dorothy Grotos voting against it. Arlington has insisted that the Metro staff tighten its financial management and reduce costs without cutting service, and has vowed to pay no more than $9 million in subsidy.

The adopted budget would make Arlington's projected subsidy about $10.2 million. Metro cannot legally compel Arlington or anybody else to make its allocated subsidy payments, so it will be interesting to see what position the Arlington County board takes on the budget Issue.

In other business yesterday, General Manager Page told the board that careless smoking by an employe was the probable cause of the pump room fire that closed the subway under the Potomac River for an hour April 17. The employe was suspended for a week, Page said.

Page said a preliminary investigation of the incident indicates that the electronic smoke sensor that first reported the fire was misread by a Metro employe and that supervisors were sent to investigate at the wrong location. That partly explained why it took 20 minutes to find the fire, despite the fact there were smoke reports from several points in the tunnels.

Page said procedural questions -- such as whether a passenger-carrying train should have been stopped in the tunnel while a supervisor checked to find the fire -- will be part of the continuing investigation.

In other matters yesterday:

The District of Columbia withdrew its request to start new bus service this summer connecting various Metro stations with the zoo, museums and other cultural locations in the city.

Page said that because of safety and ridership, he had concluded that bicycles should not be permitted on trains on weekends, as some groups had requested.