Metro is changing its bus schedules again, this time to coordinate them with the expanded subway service that begins Monday.

The new bus schedules detailed below will take effect on Sunday, but the first day of heavy impact will be Monday. On Monday the Metro subway will start staying open until midnight, Monday through Saturday, instead of closing at 8 p.m.

Beginning Sept. 30, the subway will operate on Saturdays for the first time. Saturday hours will be from 8 a.m. until midnight. There will be no Sunday subway service.

Many of the bus routes have been ajusted so that passengers may transfer from bus to train and train to bus during the expanded hours of subway service.

Extra bus service will be provided on many routes to accommodate late-evening and Saturday passengers.

In many cases, buses that ended their routes at subway stations but then continued downtown after the subway closed will operate only as far as the subway stations.

Minor scchedule adjustments will be made on many routes and riders should check with the drivers for new timetables.

At the Pentagon bus terminal, above the subway station, new bus bay assignments are being made. That means riders accustomed to arriving, leaving or transferring to one particular bus bay may find their bus moved to another. Riders should chek the new bus bay directory at the Pentagon this week.

Metro is also starting a new express bus service Monday from the Huntington Metro sation parking lot to the National Airport Metro station. The Huntington station, just south of the Beltway on North Kings Highway, will be connected by rail to National Airport sometime late in 1981, according to the present Metro construction schedule. For details on the express buses, see Virginia Routes 11F and 11G. For more detailed information, call Metro's telephone service at 637-2437.

The Metrobus route changes: Maryland Routes

Route 82 - All trips will terminate at Rhode Island Avenue Metro Station until midnight. An additional trip to Hollywood will depart Rhode Island. Avenue Metro station at 11:30 p.m. weeknights.

Routes 84, 86 and 88 - All trips will terminate at the Rhode Island Avenue station when the subway is open.

Route A12 - All trips will terminate at the Potomac Avenue Metro station when the subway is open.

Route B12 - All trips will terminate at the Potomac Avenue Metro station when the subway is open.

Route C1 - Service to CIA-Langley will be eliminated. New rush hour service between Glen Echo and Friendship Heights will be operated via Wisconsin Avenue, Old Georgetown Road, Wilson Lane, River Road and Goldsboro Road. Trips will operate every 30 minutes, Replacing Routes C1 and j7.

Routes C12 and C14 - Through service to downtown on Saturday will terminate at the Potomac Avenue Metro station.

Route D12 - All trips will terminate at Federal Center SW Metro station when the subway is open.

Route F4 - An additional trip to New Carrollton will leave the Silver Spring Metro station at 10 p.m. weekdays.

Route H12 - Evening and Saturday trips will terminate at the Potomac Avenue Metro station when the subway is open.

Route J2 - Additional trips to Montgomery Mall will leave the Silver Spring Metro station at 10:15 p.m. and 11:15 p.m. weeknights. An additional trip to Montgomery Mall will leave the Silver Spring Metro station at 10:15 p.m. Saturdays.

Route J7 - Service eliminated; passengers will continue to be served by Routes T1 and C1.

Route J12 - All trips will terminate at the Potomac Avenue Metro station when the subway is open.

Route K6 - ALl trips will terminate at the Fort Totten Metro station when the subway is open. Additional trips to White Oak will leave the Fort Totten Metro station at 11:30 p.m. and 12:30 a.m. weekdays.

Route K12 - All trips will terminate at the Potomac Avenue Metro station when the subway is open.

Route Q2 - Additional trips to Montgomery College will leave the Silver Spring Metro station at 8:15 p.m., 9:15 p.m, 10:15 p.m., 10:45 p.m. and 11:15 p.m. weeknights. An additional trip will leave the Silver Spring Metro station at 9:37 p.m. Saturdays.

Routes R2 and R6 - All trips from Maryland will terminate at the Brookland Metro station when the subway is open.

Route R12 - All trips will terminate at the Stadium-Armory Metro station when the subway is open.

1 - Additional trips will be added to increase rush-hour intervals between buses to every 30 minutes.

Route T2 - All trips will be rerouted to Montgomery College when the subway is open. Some rush hour trips will terminate or originate at Montgomery College instead of Normandy Farms.

Route T3 - New mid-day service to Woodley Gardens will be provided. Weekday trips during Mid-day will be extended from Normandy Farms to Montgomery College via T2 route to Montgomery Avenue and Nelson Street, and then via Nelson Street, Mannakee Street and Montgomery College.

Routes T4 and T6 - Weeknights and Satuday trips will be extended from Friendship Heights to Dupont Circle station when the subway is open.

Route T6 - New rush hour service to the Promenade Apartments will be operated by extending some Naval Medical Center trips via Rockville Pike and Pooks Hill Road.

Route T11 - All trips will terminate at the Stadium-Armory Metro Station when the subway is open. New trips to Beliar will be operated from the Stadium-Armory Metro station at 9:30 p.m. and 11:30 p.m. weeknights.

Route T12 - All trips will terminate at the Rhode Island Avenue Metro station when the subway is open. Additional trips to Belair will leave the Rhode Island Avenue Metro station at 11:35 p.m. weeknights and Saturdays.

Route T14 - All trips will terminate at the Rhode Island Avenue Metro station when the subway is open.

Route W12 - All trips will terminate at the Federal Center SW Metro station when the rail system is open.

Routes Y6 and Y8 - Additional trips will leave the Silver Spring Metro station at 11 p.m., 11:30 p.m., midnight and 12:30 a.m. weeknights.

Route Z4 - An extra trip will leave the Silver Spring Metro station at 10:55 p.m. weeknights.

District of Columbia Routes

Route 40 - All trips will terminate at Union Station when the rail system is open.

Route 42 - Weeknight service will be increased to every 30 minutes downtown.

Route 46 - Extra service will be provided between the Kennedy Center and Mount Pleasant when the subway is open.

Route 60 - All trips will operate via the Federal Center SW Metro station when the subway is open.

Routes 80 and 81 - All trips will operate through the Brookland Metro station when the subway is open.

Route 82 - All trips will terminate at Rhode Island Avenue Metro station until midnight. An additional trip to Hollywood will depart Rhode Island Avenue Metro station at 11:30 p.m. weeknights. See Route B6.

Routes 84, 86 and 88 - All trips will terminate at Rhode Island Avenue Metro station when the subway is open. See Route B6.

Route B6 - Additional service will be provided between the Metro Center and Rhode Island Avenue Metro stations when the rail system is open in lieu of the present through service on Routes 82, 84, 86 and 88.

Route D4 - All trips will terminate at Farragut Square on weeknights and Satursdays when the subway is open.

Route D8 - Additional trips on Route D8 will be operated on weeknights between Union Station and Ivy City. Route D8 will provide service between-Union Station and Washington Hospital Center until 8:30 p.m. on Satrusday, with Route D8 service provided thereafter between Union Station and Ivy City.

Route H6 - All trips will operate between the Kennedy Center and the Brookland Metro station when the subway is open.

Route K2 - Saturday trips will operate between the Fort Totten and Takoma Metro stations. There will be no change to weekday service.

Route K4 - All trips will operate between the Metro Center and Fort Toten Metro stations when the subway is open.

Route M6 - Saturday service will be established.

Route N4 - All trips will terminate at Farragut Square when the subway is open. Virginia Routes

Route 1A, 1B and 1H - Weeknights and Saturday trips will terminate at the Rosslyn Metro station instead of 11th and E streets NW.

Route 2A - Saturday trips will terminate at the Rosslyn Metro station instead of Union Station. Bus frequencies will be increased from every 60 minutes to every 30 minutes.

Route 2B - Saturday trips between Westover and Rosslyn will be eliminated. Replacement service is available on Route 2A.

Routes 3E, 3F, 3R, 3T and 3V - Weeknights and Saturday trips will terminate at the Rosslyn Metro station instead of 11th and E Streets NW.

Route 48 - Trips leaving Federal Triangle at 4:15 p.m., 4:35 p.m., 4:55 p.m., 5:15 p.m., 5:35 p.m. and 5:55 p.m. will be redesignated route 20G and will operate via Arlington Boulevard instead of Pershing Drive. Saturday trips will terminate at the Rosslyn Metro station instead of 11th and E Street NW.

Route 5S - Saturday trips will be rerouted via Gosnell Lane and Tyspirng Street to serve Tysons Towers.Trips will terminate at the Rosslyn metro station instead of Farraqut Square.

Routes 6A and 6B - Weeknight and Saturday trips will terminate at the Pentagon Metro station instead of Federal Triangle.

Route 6G - Rush hour trips will be extended to Braddock Road east of Early Street in front of Minnie Howard Middle School.

Route 6L - All trips will be rerouted to the Pentagon Metro station. An extra trip from Park Center will be added at 7:18 a.m. and an additional trip from Potomac Park will be added at 4:15 p.m. weekdays.

Route 7F - Weeknight and Saturday trips will terminate at the Pentagon Metro station instead of Federal Triangle.

Route 8M - Afternoon rush hour trips from Southwest Mall to Shirley Duke will operate every 30 minutes.

Route 8X - Morning rush hour service will be rerouted via the Pentagon Metro station.

Route 8Y - All trips will be redesignated 21C.

Route 9D - Route designation eliminated. See Routes 11F and 11G.

Route 10E - Weekday rush hour service will be eliminated. Alternate service is available via Routes 10S and 10T.

Routes 10S and 10T - Weekday, Saturday and Sunday trips will be extended to Hunting Towers via Washington Street. King Street, Columbus Street and Prince Street loop will be eliminated.

Route 11A - New mid-day service to River Towers will be provided via a rerouting from Belleview Boulevard to Wakefield Drive and Potomac Avenue. Two additional round trips will leave Federal Triangle and Mount Vernon during Weekday evenings and Saturday nights.

Route 11C - Weekday and Saturday trips will operate via Richmond Highway, Patrick Street, Gibbon Street and Franklin Street instead of via Fort Hunt Road, Bellehaven Road and the George Washington Memorial Parkway. Rush hour trips wil be express ad redesignated as Route 11G.Will make all stops in Fairfax County, and will stop at King and Washington streets in Alexandria and at National Airport.

Route 11E - Service to Shirley Duke via Jordan Street, howard Street, Imboden Street and Taney Avenue will be eliminated. Rush hour trips will operate every 20 minutes between Landmark and Federal Triangle.

Route 11F - This new routing provides express bus service between the Huntington Metro station fringe parking lot and National Airport and replaces service on old Route 9D. Buses will leave Mount Vernon at 6:23 a.m., 6:38 a.m., 6:53 a.m., 7:08 a.m. and 7:38 a.m. They will stop at Huntington at 6:47 a.m., 7:02 a.m., 7:17 a.m., 7:32 a.m. and 8:02 a.m. Buses will make all stops in Fairfax County but will stop only at King and Washington streets in Alexandria.

Route 11G - Rush hour express service along 11C route, will include stop at 7:48 a.m. at huntington Metro station fringe parking lot. Bus will make all stops in Fairfax County but will stop only at King and Washington streets in Alexandria.

Route 11P - New service to National Airport Metro station will be provided. Trips will leave Belvoir and Hudson roads at 6:20 a.m. and 6:50 a.m. and the Pentagon at 4:45 p.m. and 5:15 p.m. Limited stop restrictions will remain the same, except that boarding and alighting will be permitted at National Airport station.

Route 11T - New express service between Mount Vernon, National Airport and Federal Triangle will be provide by this route, which will use the 14th Street corridor instead of Memorial Bridge. Limited stop restrictions will remain the same, except that boarding and alighting will be permitted at National Airport Metro station. Trips will leave Belvoir and Hudson roads at 6:35 a.m., 7:05 a.m., 7:20 a.m. and 7:35 a.m. and Federal Triangle at 4:20 p.m., 4:54 p.m., 5:19 p.m. and 5:34 p.m.

Route 11W - Rush-hour limited stop service will be redesignated Route 11Z. Local Trips will be designated Route 11W.

Route 12F - Weeknight and Saturday trips will be redesignated Route 12A and will operate to the Pentagon Metro station instead of to Federal Triangle.

Route 14A - Weeknight and Saturday trips will be redesignated Route 12A and will operate to the Pentagon Metro station instead of to Federal Triangle.

Route 14A - Weeknight and Saturday trips will terminate at the Pentagon Metro station instead of Federal Triangle.

Route 15B - To provide faster service to the Pentagon City Metro station, all trips will be rerouted via South 15th Street and South Hayes Street instead of South Joyce Street and Army-Navy Drive.

Route 15F - Weeknight and Saturday trips will terminate at the Pentagon Metro station instead of Federal Trianle, and will be designated Route 15A.

Route 16B, 16C and 16E - Saturday trips will operate every 20 minutes. Extra trips during weekdays will be operated on Route 16E from Culmore at 9:22 a.m. Additional service on Route 16B will elave the Pentagon Metro station at 3:53 p.m. weekdays.

Route 17A - Additional trips will leave the Pentagon Metro station at 8:50 p.m. and 9:50 weekdays.

Route 18A - Additional trips will leave the Pentagon Metro station at 9 p.m. and 10 p.m. weekdays. Service to Bren Mar will be rerouted via Beryle Road, Sheldon Road, Bren Mar Drive and Indian Run Parkway. New rush hour service will operate between Springfield and the Pentagon via Amherst Avenue, Bland Street, backlick Road, industrial Road, Backlick Road, Edsall Road, Beryle Road, Sheldon Road, Bren Mar Drive, Indian Run Parkway, edsall Road and I-395. New Route 18A will replace Routes 18X and 18Y and will operate every 15 minutes during rush hours.

Route 18D - Rush hour trips between Springfield and the Pentagon will be eliminated.

Route 18E - Rush hour trips will operate via the Pentagon Metro station. Some trips will provide express service to Federal Triangle during rush hours.

Route 18H - New rush hour service to Rolling Valley will be provided via Arley Drive, Rockfeller Lane and Huntsman Boulevard.

Route 18K - New service to Orange Hunt will be provided via Keene Mill Road, Huntsman Boulevard, Sydenstricker Road, Field Master Drive and Conservation Drive.

Route 18M - Rush hour trips between West Springfield and Southwest Mall will operate every 30 minutes.

Routes 18X and 18Y - rush hour trips betwen Springfield and the Pentagon will be eliminated. Alternate service will be available on Routes 18A and 18E.

Route 20G - New rush hour service between Culmore and the Rosslyn Metro station will operate via Leesburg Pike, Patrick Henry Drive, Arlington Boulevard, meade Street, Lynn Street, 19th Street and Moore Street. Trips will leave Culmore at 7:11 a.m., 7:31 a.m., 7:51 a.m. and 8:21 a.m. and rosslyn at 4:40 p.m., 5:10 p.m., 5:30 p.m. and 5:52 p.m.

Route 21A - This is a new designation for previous Route 27E service between Landmark and Federal triangle.

Route 21B - This is a new designation forprevious Route 27F service between Landmark and the Pentagon station.

Route 21C - This is a new designation for previous Route 8Y service between Quaker Land and the Pentagon and Federal Triangle.

Route 23B and 23E - All trips will be rerouted to Courthouse Road between South 2nd Street and Columbia Pike instead of via South 2nd Street, Uhle Street and Washington Boulevard.

Route 27B - This is a new route to serve the Windsor Park community in Franconia via Beulah Street, Hillary Street and Silver Ridge Circle. Previous routing via Franconia Road, Telegraph Road, The Parkway and South Kings Highway will be eliminated. Trips will leave Windsor Park at 6:42 a.m., 7:12 a.m. 7:42 a.m. and 8:22 a.m. and the Pentagon at 4:40 p.m., 5:05 p.m., 5:35 p.m., 5:55 p.m. and 6:25 p.m.

Route 27E - Service between Landmark and Federal Triangle is redesignated Route 21A.

Route 27F - Service between Landmark and the Pentagon Metro station is redesignated Route 21B.

Route 27H - Weeknight trips will terminate at the Pentagon Metro station instead of Federal Triangle.

Route 27K - Rush hour service between Virginia Hills and Federal Triangle will be eliminated.

Route 27P - Rush hour trips will operate every 30 minutes. Trips will leave Springfield Mall at 6:40 a.m., 7:10 a.m., 7:40 a.m., 8:10 a.m. and 8:30 a.m. and the Pentagon Metro station at 4:25 p.m., 4:45 p.m., 5:15 p.m., 5:40 p.m. and 6:10 p.m.

Route 27W - This is a new route providing rush hour service between Beacon Hill and the Pentagon via Southgate Drive, South Kings Highway, The Parkway, Telegraph Road, Burgundy Road, East Drive, Elmwood Drive, Norton Road, Franconia road, [WORD ILLEGIBLE] Street, Capital Beltway and [WORD ILLEGIBLE] Highway. Trips will leave Beacon Hill at 6:31 a.m., 6:58 a.m. and 7:28 a.m. and the Pentagon at 4:50 p.m., 5:20 p.m. and 5:50 p.m.

Route 29E - Trips will be rerouted via the Pentagon Metro station and the 14the Street corridor to 10th and Constitution Avenue, using E Street and Pennsylvania Avenue. Some rush hour trips willbypass Pentagon station.

Route 29L - Extra weeknight trips will leave the Pentagon Metro station at 9:20 p.m. and 10:20 p.m.

Route 29Z - Trips will operate every 15 minutes, with one morning trip and one evening trip eliminated.