Twenty-seven "underutilized" trips on 12 bus routes in Montgomery County, which run primarily in the early morning or late evening, will be eliminated in either September or January.

The decision will depend on the outcome of negotiations between Metrobus officials and the county's Department of Transportation during the next several weeks, according to Genevieve Leary, assistant chief for Montgomery's division of transit services.

The county requested the September route reductions in January and claims that the longer Metrobus "stalls" in the implementation of the new schedules, the more money Montgomery continues to spend on the trips.

Metrobus says it needs the four extra months to prepare new work schedules for bus operators that also will include the extension of two trips and the addition of a third.

September route schedules were to have been filed last week, according to Bob Sauer, bus operations specialist for Metrobus. Because the Metro board approved the reductions only two weeks ago, there was not enough time to include the changes in the fall schedule, he said.

The route changes coincide with the September opening of Metrobus' ninth garage--and the first in Montgomery County--near the White Flint shopping mall. The trips to be eliminated currently carry an average of either none, one or two passengers, said Leary, adding that the county's subsidy payments to Metro are expected to decrease by $150,000 for the year following the route reductions. Metrobus estimates that its operating costs in Montgomery County will be reduced by $50,000 annually.

The service cutbacks are consistent with Montgomery's policy that at least 20 percent of costs be recovered from farebox revenues on specific routes, route segments, or during specific time periods operated.

On Route C2, Beltway Plaza-Montomery Mall Line, a 6:05 a.m trip will be added. The route extensions are on the 3:34 p.m. trip from Langley Park to Montgomery Mall and the 7 p.m. trip from Beltway Plaza to Kensington.

The following routes will be eliminated:

Routes J2, J4, Bethesda-Silver Spring Line: weekdays, 11:50 p.m. Silver Spring-NIH; 9:52 p.m. Silver Spring-Friendship Heights; Saturdays, 8:45 p.m. and 9:45 p.m. Silver Spring-Friendship Heights (cutback to Bethesda); 9:45 p.m. Friendship Heights-Silver Spring-Bethesda.

Route N4, Massachusetts Avenue Line: weekdays, 11:33 p.m. and 12:08 p.m. Glen Echo-Ward Circle, 6:01 a.m., 6:29 a.m., 7:03 a.m., 7:16 a.m. 7:37 a.m. and 7:46 a.m. Westmoreland Circle-Glen Echo.

Route T1, Bradley Boulevard Line, weekdays, 6 a.m. Friendship Heights-Congressional Country Club; 7:30 p.m. and 8 p.m. Congressional Country Club-Friendship Heights.

Route T2, River Road Line, weekdays, Saturdays and Sundays, 11:40 p.m. Montgomery College-Dupont Circle.

Routes T-4 and T-6, Bethesda-Rockville Line, weekdays, 12:50 a.m. and 1:17 a.m. Montgomery College-Dupont Circle.

Routes Y7 and Y8, Georgia Avenue Line, weekdays, 8:55 a.m. Bel Pre Road-Silver Spring; 12:35 a.m. Silver Spring-Bel Pre Road.

Routes Z2, Colesville Road Line, weekdays, 5:50 a.m. Silver Spring-Olney Road; 8 p.m. Olney Road-Silver Spring.

Route Z4, Randolph Road Line, weekdays, 10:54 p.m. and 11:24 p.m. Randolph Road-Silver Spring.

Two trips also were eliminated from the L Routes. However, their times are currently unavailable due to schedule revisions.