In a move some members cited as a dangerous precedent, the Metro board voted yesterday to reinstate one of the bus routes it had truncated in an attempt to eliminate parrallel bus and subway service and thus save money.

The route, the 11Y bween Mount Vernon and Farragut Square, was cut off at the National Airport Metro station Sept. 9 as part of a massive realignment of 180 routes that changed the buses into feeders for the subway's new Blue Line.

The board also approved bus service adjustments in the Benning Road/II Street Lines to alleviate problems that have occurred there because of the Sept. 6 schedule realignment.

But the 11Y was seen by board members as more significant in terms of maintaining the concept of nonduplicative bus-rail service, particularly on routes connecting Northern Virginia with the heavy employment zone along I Street, K Street and Connecticut Avenue.

The issue passed' 5 to 1, with only Arlington County Board member Joseph Wholey voting no.

The Fairfax County Board had asked Metro to reinstate the 11Y after well-organized group of 11Y rider-complained that their transfer at National Airport was costing them both time and money.

The Metro board usually respects requests from individual jurisdictions when the impact is local and not regional.

"Local courtesy appears to be the policy of the board." Montgomery County member Cleatus Barnett observed after voting to reinstate the 11Y. "But if we continue along this line it will be nothing short of financial disaster."

Formal opposition to the reinstatement also was lodged by the Metro staff and by the Northern Virginia Transit Commission. Both bodies are well aware that there is conserable unrest among the many Northern Virginia bus riders whose routes have been cut off at the Pentagon or Roslyn and who have been virtually forced to take the subway to work.

Joseph Alexander, a member of the Fairfax County Board, conceded that other bus riders, particularly those accustomed to the Shirley Highway express service, who would request that routes be reinstated. He told the board be reinstated. He told the board that with some schedule changes and slight modifications that he would propose next week many problem could be solved.