Cuts in Metrobus service for Northern Virginia, far less drastic than originally proposed, were approved last week by the Metro board and will take effect April 12.

About a dozen lines will be affected, chiefly by elimination of a few individual trips or termination of little-used trips at the Pentagon subway station instead of in downtown Washington.

The Metro decision was a clear victory for Northern Virginia riders, who turned out in large numbers at hearings last fall to protest plans for large-scale reductions. These would have included almost total elimination of Saturday and Sunday service in Fairfax County. A total of 67 persons spoke against the changes, and Metro received 159 letters and petitions with 1,300 signatures taking similar views.

As the board prepared to vote on the matter last week, its new chairman, Fairfax County Supervisor Joseph Alexander, said Metro will have to find new ways to economize. "Cutting service is not the way to go," he said.

The board already had approved similar service reductions in the District and suburban Maryland. While the Metro board makes the final decision, it almost always does what the affected local cities or counties want, since local taxes pay for the operating deficits of the transportation system.

As a result of last week's decision, Metro will lose an estimated $145,000 annually in fares, while saving an estimated $602,000 per year on operating costs -- meaning Fairfax County will be able to trim its Metro subsidy by $457,000 a year.

Although Fairfax County is one of the nation's most affluent and automobile-dependent communities, Metro staff members said a survey found many bus riders "rely on the (bus) service (on weekends) to get to jobs and make essential shopping trips" and that the originally proposed cuts would "leave them stranded." It also found that buses to Tysons Corner, Seven Corners and Springfield Mall shopping centers are heavily patronized.

Reductions and service changes approved for Northern Virginia:

Route 2C -- Two late-evening trips from Ballston subway station to Tysons Corner will be changed to Route 2M and will terminate at Merrifield.

Route 4A -- All Saturday and Sunday service and one late weekday trip from the Rosslyn subway station will terminate at Seven Corners instead of Culmore.

Route 5B/5G -- One early-morning trip on each of these branches of the Reston Express route will start at the entrance to the Dulles Airport Highway access ramp instead of their present terminals. No other changes will be made in the current schedule.

Route 11A -- Sunday service will run only to and from Mount Vernon Circle and not all the way to the Hudson Road entrance to Fort Belvoir. Four weekday rush-hour trips in each direction will terminate at Vernon View Drive and the George Washington Memorial Parkway in the Fort Hunt area rather than running all the way to and from Fort Belvoir. (An earlier proposal to terminate most of the service at Hunting Towers in Alexandria was dropped.)

Route 11B -- All Sunday service on this route, which runs to and from the Virginia Hills-Rose Hill area southwest of Alexandria, will be discontinued.

Route 17 -- Several morning and evening buses to and from Kings Park will terminate at the Pentagon subway station instead of the Federal Triangle in downtown Washington.

Route 18 -- Several morning and evening buses to and from Springfield will terminate at the Pentagon instead of the Federal Triangle, while others that now go directly to and from Washington will be looped through the Pentagon station. Several trips that now run between Springfield and the Pentagon will be discontinued.

Route 19G -- One morning inbound trip from Huntington to the Federal Triangle and two evening outbound trips will terminate at the Pentagon.

Route 20E -- All express trips to and from Oakton will terminate at the Pentagon instead of the Federal Triangle.

Route 27 -- One morning inbound 27G trip from Hayfield and two evening outbound trips will terminate at the Pentagon instead of the Federal Triangle. One late-evening outbound 27H trip will terminate at Springfield Mall instead of Hayfield.

Route 28G -- Three outbound trips leaving the Federal Triangle for Skyline Center after 6:30 p.m. will start at the Pentagon.

Route 29E/29G -- some trips between Annandale and the Federal Triangle in the morning and evening rush hours will terminate at or be looped through the Pentagon station.

Route 29Z -- Two inbound morning trips from Greenbriar and three evening outbound trips from the Federal Triangle will terminate at the Pentagon.

In addition to the changes listed above, all Route 9 service through Ft. Belvoir will operate after April 12 along the present 9A routing, eliminating two route variations considered to be confusing, and the detour currently being used by all Route 16 buses in the Heritage Mall area of Annandale will be permanent.