This is a peak season for bicycle accidents in the District, according to the Washington Area Bicyclist Association, which recently issued a report naming the city's most dangerous intersections and roads for bicyclists.

Of 12 intersections where accidents between cyclists and motorists occur most often, Observatory Circle, at 34th Street and Massachusetts Avenue NW, was worst.

The most dangerous roadway, the study said, is a 1 1/2-mile stretch of upper 14th Street NW, between S and Quincy streets. It was also the longest among 22 sections of streets labeled dangerous to cyclists.

Although the D.C. Department of Transportation issues annual reports on bicycle and pedestrian accidents, the WABA report is the first to make a comparison of figures for several years, WABA safety committee chairman Carl Modig said. The report is based on information gathered by the D.C. Police and the National Park Service in 1972, 1973 and 1978 through 1981.

In the six years studied, 12 accidents occurred at Observatory Circle. The intersection is dangerous "maybe because several roads come in at once and there's also a hill," Modig said.

Bicyclists traveling southeast on Massachusetts Avenue have a problem stopping because of the 30-mph speeds they can reach coming downhill near the circle, said Sgt. Dave Clinesmith of the police traffic division.

Sixty-one accidents were reported on the 1 1/2-mile section of 14th Street. Officer Fred Thompson, a traffic analyst for the police department, said many children and teen-agers congregate in the area. "There aren't that many areas where children can play around here except riding in the street," Thompson said.

The transportation department designated a section of 13th Street NW as a bike route in an attempt to divert bike traffic from 14th Street after recognizing the danger it posed to cyclists.

About 500 accidents between bicyclists and motorists are reported annually in the District, a fraction of the actual number that occur, Modig said. Sometimes the bicyclist believes the accident is not serious enough to call the police, he said, or the police do not fill out an accident report unless there is injury or enough damage to make the bike inoperable.

Reported accidents declined from 547 in 1981 to 519 in 1982. "We're holding our breath to see if it continues to go down," Modig said.

Based on judgments made by the investigating officers, cyclists are responsible for about half the reported bicycle-auto accidents, according to another WABA report released in April. The car driver is to blame for 35 to 40 percent and the rest are attributed to both parties, bad weather or visibility, WABA said.

In the last five years, six people have died in bicycle-auto collisions, four of them in night accidents. "Bicyclists shouldn't ride at night," Modig said. "If they have to, they should rely on more than just reflectors. They need lights."

Bart Cima, chief of the Department of Transportation's neighborhood traffic management branch, said the agency plans to investigate the most dangerous sites WABA listed and will seek solutions. WABA has suggested posting warning signs for motorists and bicyclists or creating a lane for bicycles.