New bus service designed to aid the handicapped and the elderly begins Sunday when the Washington Metropolitan Area Transit Authority inaugurates lift-equipped bus service on 12 routes.

The new buses have platforms which can be lowered to the curb so passengers can board buses without to 32 routes this fall.

The lift-equipped buses will not be operated on every trip of the 12 routes going into service Sunday. Trips where lift buses will available will be marked with a "w" on the timetables. Buses with the lift feature are clearly marked at the front door with the words "Wheelchair Lift Equipped" and the wheelchair symbol.

To obtain timetables, call 637-1261.

A brochure explaining how to use lift-equipped bus is available by calling 637-1179. Demonstrations on use of the lift buses also are being given. For information on the demonstrations, call 637-1256.

Handicapped and elderly people ride Metrobuses at reduced fares. Handicapped passengers should call the transit authority at 637-1245 or 637-1246 to find out how to get an identification card to use on the bus. People 65 and older may take proof of age to any public library to receive an identification card.

The new buses will operate on certain trips on the following routes:

Route 9: Fort Belvoir Line - serving Fort Belvoir, DeWitt Army Hospital, Mount Vernon, Hunting Towers, downtown Alexandria, Crystal City, Pentagon, Bureau of Printing and Engraving and 10th and Pennsylvania Avenue NW.

Route 10: Alexandria-Rosslyn Line - serving Hunting Towers, Del Ray, Arlandria, Shirley Park, Shirlington, Westmont, Parkington, Virginia Square, Claredon, Fort Myer and the Rosslyn Metro station.

Routes 30, 32, 34 and 36: Pennsylvania Avenue Line - serving Friendship Heights, Wisconsin Avenue, M Street, George Washington University Hospital, Pennsylvania Avenue, 15th Street and Pennsylvania Avenue SE, Shipley Terrace, Naylor Gardens and Hillcrest.

Route 40: Mount Pleasant Line - serving Mount Pleasant, Union Station/Visitors Center, RFK Stadium, Stadium-Armory Metro station and Seat Pleasant.

Routes A2, A4, A6 and A8: Anacostia-Congress Heights Line - serving the Greater Southeast Community Hospital, D.C. Village, Bellevue, Fort Drum, Livingston, Wheler Road and Varney Street, Federal Center South-west Metro station and 10th Street and Pennsylvania Avenue.

Routes D2, D4 and D8: Glover Park-Trinidad Line - serving Glover Park, Sibley Hospital, Trinidad, Ivy City, Rhode Island Avenue Metro station and the Veterans Administration Hospital.

Routes F4 and F6: Prince George's-Silver Spring Line - serving the Silver Spring Metro station, Prince George's Plaza, East Pines, New Carrollton Metro station, University of Maryland, Beltway Plaza and Greenbelt.

Route M6: M Street-Visitor Center Line - serving Rosslyn, Georgetown, Federal Triangle, Capitol Hill and the Union Station/Visitor Center complex.

Routes S2 and S4: 16th Street Line - serving the Silver Spring station, 16th Street and Federal Triangle.

Routes T4 and T6: Bethesda-Rockville Line - serving Montgomery College, Rockville, Naval Medical Center, National Institutes of Health, Bethesda, Friendship Heights and Dupont Circle.

Route T17: John Hanson Highway Express Line - serving the Belair Center and the New Carrollton Metro Station.

Routes X4 and X6: Benning Road Line - serving the Minnesota Avenue Metro station, Mayfair Gardens, 34th Street and Benning Road, Union Station/Visitors Center and Lafayette Square.