A federal judge yesterday upheld sweeping government regulations designed to open up the nation's federally funded transportation systems to millions of handicapped passengers.

The decision by U.S. District Court Judge Louis F. Oberdorfer was seen as a major victory by coalitions of handicapped persons who have long fought to make bus, subway and commuter rail systems accessible to the disabled.

The regulations, passed by the Department of Transportation, require that public transportation systems be made accessible to the handicapped within three years, with extensions up to 30 years in cases were highly expensive structural changes must be carried out. Compliance costs are estimated at from $3 to $7 billion dollars, some of which would be paid by the federal government through transportation grants to the localities.

Oberdorfer's decision, upholding the authority of the secretary of transportation to pass the regulations, left it to Congress to evaluate the economic and technical questions raised by the regulations. Congress is currently considering whether to fund the changes though transit grants or whether to seek modifications.

The regulations state that half of all buses, all key subway and commuter rail stations and one car per train must be accessible to wheelchair users.

All federally funded buses and subway cars acquired after July 2, 1979, must also be accessible to wheelchair users, as well as new commuter rail cars purchased after Jan. 1, 1983.

More than $3 billion in federal mass transit grant money hinges on compliance with the regulations, Oberdorfer said in his opinion.

The effect of the regulations is expected to be minimal in the Washington area, where the Metro subway system was constructed to facilitate handicapped riders. More than 100 new Metro buses can accept lifts for riders confined to wheelchairs.

The biggst impact will be in large cities with old and massive rail transportation systems, such as New York and Chicago. Congress has instructed the Department of Transportation to make funds available to transit operators to prepare detailed estimates on the cost of refitting their subway, streetcar and commuter rail systems to serve the handicapped. The reports are expected to be forwarded to Congress in August.

In the meantime, Congress has said that no federal funds should be spent in 1980 to overhaul existing rail systems to meet the regulations requirements. i