WASHINGTON Ongoing security concerns apparently are costing motorcoach operators that visit the Capitol Mall here their traditional passenger drop-off spots, plus a short-term parking area.

Drivers report being issued tickets from Capitol Police for discharging passengers in front of the national museums that line the mall, and for parking for short periods in an area adjacent to the American Indian Museum.

"They're getting $50 tickets now," said Chuck Andrews of World Strides, the industry's largest operator of Washington D.C. tours for students.

He said police have told drivers that the only place they are allowed to drop-off passengers is in front of the Indian Museum, which is near the eastern end of the 1.9-mile-long mall.

He said drivers reported last month seeing as many as 30 police officers on foot, horseback and scooters issuing tickets in front of the museums on the mall.

A spokesman for the National Park Service acknowledges the agency has made changes to the passenger drop-off and parking regulations for motorcoaches, but he insisted he could not discuss details until he prepares an official news release, which he said could take several days.

"The changes were made for security reasons and I am sure people can understand that," said Bill Line, a public affairs officer for the Washington regional office of the Park Service.

Motorcoach drivers for years have been dropping off passengers in front of most of the museums and either staying there for a brief period while the passengers took pictures or leaving the area and parking elsewhere while the passengers visited the attractions. In addition, drivers have been using the parking near the Indian museum without any problems.

Andrews, whose company brings between 300,000 and 400,000 students to the mall a year, said the drop-off restrictions could make it difficult for the elderly or disabled to visit some of the museums because they are distant from the Indian museum.

For example, the Indian museum is about one and one-half miles from the Museum of American History, which is one of the most popular stops on the mall and which is undergoing a major renovation.

He said some drivers have been told by mall police they could drop off passengers and park on Massachusetts Avenue, but the street is too busy and would be dangerous for school children.

"I dont think that would be a good street to use," he added.

Line was unable to say exactly why the Park Service made the changes without notifying the motorcoach industry, which brings hundreds of buses and thousands of visitors to the mall every day.

He noted, however, that regulations governing the mall are complicated and the large number of people who visit the mall an estimated 25 million every year make regulatory issues even more difficult. "Its not like 'See Jane run, see Dick run,' " he said.