Many streets and bridges in the District of Columbia are in such critical need of repair that the city government is planning to fix them with money that could have been used for the Metro subway systems, D.C. Transportation director Douglas Schneider told the Metro board yesterday.

The money would come from funds originally earmarked for interstate freeways in Washington. Almost $1 billion in federal money for interstate highways within the beltway has been diverted to Metro. About another $1 billion is available for such purposes. Under federal law, that money can also be used for highway projects other than interstate.

The Districtis planning to tranfer about $465 million from its federal interstate account. The lion's share of that money will go to Metro, but about $90 million will be used for road improvement projects, according to James Clark, planning director for D.C.

Primary among them are the replacement of the Michigan Avenue bridge over the Metro and E&O tracks in Northeast Washington and a n*ew deck on the Whitney Young (East Capitol Street) Bridge. Major repairs are also planned for the Connecticut Avenue bridge over Klingle Valley in Northwest for the Benning Road-bridge near Kenilworth Avenue, for South Dakota Avenue near Fort Lincoln and for South Capitol Street at Southern Avenue. All of those road-stand bridges have badlydeteriorated paving and two consecutive harsh winters have exacerbated the problems.

Also at the Metro board yester day:

D.C. council member Jerry A. Moore, a member of the Metro board, said that city is considering a small-bus network in parts of Washington similar to the Ride-On program that has had great success in Montgomery County. Moore said his office has received many complaints from thebrookland area since Metrobus routes were rearranged in conjunction with the extension of the Metro sub-way through Brookland to Silver Spring.

The board approved plans by the District of Columbia to construct new bus bays at the Potomac Avenue Metro station. The construction to be completed by July 1, would make it possible for homebound commuters to transfer from subway to buses directly in front of the station. At present passengers have to clomp across six lanes of Pennsyivania Avenue SE, and they have complained about if. Potomac Avenue is a major bus and subway-transfer point for Prince George's County residents.

Laline O.Harris, the principal of Woodson Junior High School at 4101 Minnesota Ave. N.E, asked in a letter to Moore that Metro improve security around the Metro line under construction near the school. The line, part of the section to New Carrollton that is due to open in November, is above ground at the point. Harris reported that school children and other have climbed or cut the security fences along the line to cross the tracks.

The section of track will be electrified in late April or early May as Metro begins operating tests on the section.

There is a tunnel under the tracks that will be used by Metro riders to enter and leave the Minnesota Avenue station. That tunnel can also used to go under the tracks without entering the station. Harris said that "parents and faculty . . . expressed concern and objected to an underground tunnel below the surface rails as a thruway." The Metro staff promised to study the issue.

The transfer of interstate highway money has "saved" the Metro construction program, in the word of U.S. Transportation Secretary Brock Adams. The Washington area begin to use interstate money after construction costs exceeded the original $2.5 billion cost estimate for Metro.

Schneider's announcement yesterday will not affect money that has been committed to completing 60 miles of the planned 100 miles subway system. But some of the $90 million to be shifted to highways has been regarded by Metro officials as a source of funds to purchase more rail cars for the system.

Metro has received most of its original order of 300 cars, and they will be enough to operate planned Metro extensions through most of 1980. However, more cars will be needed by the end of 1980, when Metro is scheduled to open extensions on the Red Line from DuPont Circle to Van Ness Center and on the Blue Line from National Airport to Huntington.

Money must be found to buy more cars and an order must be placed quickly for the cars to be ready by then, Metro officials have told the board.