Metro will offer free subway and bus rides home from downtown Washington Wednesday night after the annual Fourth of July fireworks display.

Passengers will pay regular holiday fares on trains and buses until 9 p.m. Wednesday, just before the fireworks display starts at 9:15 p.m. For the rest of the night on the trains and until midnight on the buses, on fares will be collected.

Metro Officials plan to operate full subway service and extra bus service Wednesday, to carry people to and from the fireworks display and other events in downtown Washington.

Metro officials said the free rides are intended to avert long lines at fare gates in subway stations and to permit fast loading of buses as thousands of riders are expected to swarm onto Metro vehicles during a short period after the display.

The free ride policy was tried last July 4, and proved so successful that Richard S. Page, Metro general manager, recommended that it be repeated this year. The Metro board agreed.

Mindful of a fiasco on July 4, 1976 -- when Metro failed to dispatch enough buses to carry spectators home from the Bicentennial fireworks display, thereby stranding thousands for hours downtown -- Page said he and other top officials will take direct charge of operations.

Since there is only one subway station directly on the Mall where the fireworks display will be - the Smithsonian station on the Blue Line - Metro Officials appealed to riders to use other stations throughout the downtown and Southwest areas. They especially urged that riders on the Red Line avoid transferring to the Blue Line at Metro Center for the short ride to Smithsonian, which would overburden that often-congested station.

The Red Line runs from Silver Spring to Dupont Circle. The Blue Line runs from National Airport to New Carrollton. One of its Virginia Stops, Arlington Cemetery, is close to an area with an excellent view of the fireworks display. The cemetery station usually is closed at night, but will be open on Wednesday.

Following is a rundown of Metro's announced operations on Wednesday:

TRAIN SERVICE -- Trains are scheduled to run every 10 minutes on both lines from 8a.m. to 6:30 p.m. is 50 cents; each rider must have his own Farecard.

PARKING LOTS -- Parking at all lots operated by Metro will be free all day. These are located at Silver Spring, Takoma, Fort Totten, Rhode Island Avenue, New Carrollton, Landover, Cheverly, Deanwood and Minnesota Avenue stations.

Parking at Stadium-Armory station, operated by the D. C. Armory Board, will cost $1. Parking at Pentagon City, operated privately, will cost $1.25.Parking in a Montgomery County garage on Second Street near the Silver Spring station will be free.

Free parking also will be provided in the Pentagon north lot, and Metro will run free shuttle buses to the Pentagon and Arlington Cemetery stations.

BUS SERVICE -- In addition to the regular Sunday service, Metro will provide extra service on many bus routes and will operate on some where no buses usually run on Sundays or holidays.

There is no published timetable for the extra service. Metro supervisors have been instructed to check street corners and provide enough buses to meet the need. Fares range from 40 to 80 cents. In most instances, the special buses will run to a subway station, and a separate 50-cent buses will go all the way downtown. A list follows of the routes on which extra service will be provided.

D.C. AND MONTGOMERY COUNTY

Route 30, Friendship Heights to Archives; 32, Shipley Terrace to Potomac Avenue; 34, Naylor Gardens to Potomac Avenue; 36, Hillcrest to Potomac Avenue; 40, Mount Pleasant to Bureau of Engraving; 50, 14th Street and Colorado Avenue to Bureau of Engraving; 60, 11th and Monroe Streets NW to Archives; 70, Georgia and Eastern Avenue NW to Archives; 82, Hollywood to Rhode Island Avenue; A2, Congress Heights to Easter Market; A8, Livingston to Eastern Market; K6, White Oak to Fort Totten; £2, Chevy Chase to Federal Triangle; £4, Wheaton to Federal traingle; N4, Friendship Heights to Federal Triangle; S2, Georgia and Alaska avenues Nw to Federal Triangle; U4, Sheriff Road to Minnesta Avenue; V4, Minnesota Avenue and Ridge Road to Potomac Avenue, and Y6, Wheaton Plaza to Silver Spring.

PRINCE GEORGE'S COUNTY

Route 82, Hollywood to Rhode Island Avenue; A12, Capital Plaza to Deanwood; D12, Marlow Heights to Federal Center Sw; H12, Temple Hills to Potomac Avenue; J12, Andrews Air Force Base to Potomac Avenue; K19, Penn Marr to Potomac Avenue, and W12, Padgetts Corner to Federal Center SW.

VIRGINIA

Route 1A, Annandale to Rosslyn 1B, Woodburn School to Rosslyn; 2A, Merrifield to Rosslyn; 3V, Tysons Corner to Rosslyn; 4G, Culmore to rosyln; 5W, Oakton to Rosslyn; 6b, Pendleton Street, Alexandria, to Pentagon; 7F, Lincolnia to Pentagon; 9A, Fort Belvoir to Pentagon; 11a, Mount Vernon to National Airport; 11E, Landmark to National Airport; 14A, Royal Street, Alexandria, to Pentagon; 16E, Heritage Mall to Pentagon; 18E, Springfield to Pentagon, and 20M, Fairfax to Rosslyn.

MONTGOMERY COUNTY RIDE ON

In addition to regular Sunday schedules, extra service will be available on routes 3, Wheaton to Silver Spring; 12, Silver Spring to Takoma, and 15, Langley Park to Silver Spring.

INFORMATION

Metro, 637-2437. Montgomery County Ride-On, 468-4100.