The financially strapped Metro transit authority approved plans yesterday to halt most bus service across the 14th Street Bridge between the District Columbia and Northern Virginia--a move expected to cause delays for nearly 8,000 commuters.

The plan, scheduled to go into effect June 28, was adopted by Metro's board of directors in an attempt to save $1.7 million a year by eliminating bus routes that overlap newly opened subway lines. Bus service over the 14th Street crossing will be reduced shortly after rail service starts on Metro's new Yellow Line between downtown Washington and Northern Virginia.

The planned curtailment of bus service has stirred objections from many commuters, who complained at public hearings that they will face inconvenience and delays if they must transfer from buses to subway trains. Bus lines in Northern Virginia that now traverse the 14th Street Bridge will end at the Pentagon.

According to Metro officials, the change will reduce fares slightly but increase commuting time by 5 to 15 minutes for about 7,900 passengers. "For those people, it will mean a certain lessening of the quality of service in their minds," Millard L. Seay, a bus operations specialist, said yesterday.

At the same time, the opening of the Yellow Line, set for April 30, will result in quicker rail trips for many other riders, Metro officials say. Yellow Line service, initially scheduled to link the Gallery Place and National Airport stations, will offer shorter rides between parts of Northern Virginia and the downtown area than Metro's Blue Line provides.

While ending most bus service across the river, Metro officials plan, nevertheless, to start operating a new shuttle bus line, to be called the Route 13, from the Pentagon across the 14th Street Bridge to the District. In response to some commuters' complaints, the authority agreed to enlarge the shuttle's proposed routes to include the Capitol Hill area and to schedule it to run more frequently--every 10 minutes during rush hours.

The bus cutbacks are the latest in a series of curtailments that have ended most service between Virginia and the District in recent years. Other bus routes were cut after rail service started on the Blue and Orange Lines. The bus routes scheduled to stop at the Pentagon in June include the 6, 7, 8, 9, 12, 14, 15, 16, 17, 18, 19, 21, 27, 28G and 29 lines.

In another move, the Metro board approved a plan allowing bicycle riders to take their cycles on trains on weekdays after 7 p.m. as a six-month experiment, starting May 2. Bicycles are now permitted on subways on weekends and holidays.