A citizens committee studying ways to reduce school busing in Prince George's County has decided to study the effects of requiring elementary schools to have no less than 20 percent nor more than 80 percent black enrollments.

The study, expected to be ready in two weeks, is the second initiated by the school system's advisory committee on busing. The first showed that eliminating busing for desegregation would result in resegregating the county's elementary schools.

The federal court order desegregating the school system in 1973 called for a 10-to-50 percent range of black enrollments in each school. Those limits have since been exceeded because of changing population patterns.

The committee's initial study, released earlier initial, released earlier this month, allowed only for busing within individual school attendance boundaries rather than busing to achieve desegregation.

The committee said the new study should include a requirement that schools with fewer than 300 students that fall outside the 20-to-80 percent black enrollment range should be closed.

The maximum time allowed for busing students to schools would be lowered from 35 to 30 minutes. "We just felt that 35 minutes was too long to bus an elementary school child," said Emerson Markham, committee chairman.

Markham said the committee thinks "the racial balance will be much better in the second study."

The busing issue, complicated by changing population patterns, has vexed the county school board for two years. Appointment of the study committee resulted from inability of board members to agree on a plan to reduce busing.

The goal the committee will study next -- a range of 20 to 80 percent black enrollment -- results from committee agreement on a 25 to 75 percent range with a 5 percent margin of error.