When the X-8 Metrobus pulled in at Union Station yesterday morning Margaret Hull was confronted with an unpleasant dilemma: either a slower or a more expensive trip to work.

No longer could Mrs. Hull ride the X-8 all the way from her Northeast Washington home to her downtown job as a clerk at Riggs National Bank. Instead, she had to get off the 8 at Union Station and switch either to the subway or to another bus. The subway trip would have meant an extra 40 cent fare. But transferring to a second bus, she later discovered, added 15 minutes to her rush-hour commute.

"To me, it's a big mess," Mrs. Hull remarked, as she waited in front of Union Station to board the second bus.

Like Mrs. Hull, hundreds of other bus riders from Northeast Washington found their trips to work disrupted yesterday as the Metro transit system - under pressure from local governments - instituted changes in numerous routes. The route changes were an attempt to cut costs by eliminating overlapping bus and subway service.

In addition to the X-8, such lines as the U-6, U-8 and 40 ended their trips yesterday at Union Station, instead of continuing downtown. These lines travel on Benning Road. Maryland Avenue, H Street and East Capitol Street.

Many commuters expressed bewilderment, anger, and resentment as they poured off their buses at Union Station yesterday.

In theory, the bus riders whose lines were shortened should have switched to the subway for the remainder of their trips to work. In practice, many passengers whose bus lines were terminated at Union Station yesterday balked at riding the subway, saying they were unfamiliar with it and unwilling to pay the extra fare. Instead, they used their free bus transfers to board another bus.

"People are not going to pay two fares in the morning to get to work," Garry Bishop, a salesman at an office supply store, said as he waited to transfer to a second bus in front of Union Station. He had decided not to ride the subway to work, he said, because of the additional fare.

The afternoon rush hour brought about an apparent shift in the trend. Some commuters who had disdained the subway in the morning resorted to it on their way home. Their explanation was, in a word, money. Although switching from bus to subway entailed an extra fare, transferring from subway to bus was free.

In the huge Union Station-National Visitor Center complex, confusion abounded as bus riders wandered about in search of bus stops. Signs pointing to bus stops and the subway station were inadequate, some Metro officials conceded. Officials were deluged with questions.

"I'm looking for the subway," Evelyn Lee, a mail service supervisor at Georgetown University Hospital, said as she walked in the wrong direction through the visitor center. "I missed my turn."

Other said they resented the shortening of their bus lines. "To me, it seems they're somewhat forcing you to ride the subway," Geralding Anderson, a Federal City College student, asserted. She refused and transferred, instead, to a second bus.