The government could buy specially equipped automobiles for severely handicapped persons for about the same cost as modifying the nation's buses and subways so that people in wheelchairs can board them, the Congressional Budget Office said in a new report.

And if the money were put into such cars, about four times as many people would benefit, the report said.

The report is certain to add substantial heat to an already warm debate between organizations representing the handicapped and transit company oficials around the country on what should be done to make transit more available for handicapped persons.

The Transportation Department has proposed regulations that would require lifts on all new buses and restructuring many subway and commuter rail stations in the United States to make them accessible for persons in wheelchairs. It is already accepted that new subway systems, such as Washington's, will be equipped with elevators and other features to make them accessible.

Enactment of the regulations, the CBO said in its report, would cost an estimated $6.8 billion over the next 30 years and would "serve no more than 7 percent of all severly disabled persons."

"When the cost of implementing the DOT regulations is spread over this limited number of wheelchair users and other severely disabled passengers," the report said, "the plan costs approximately $38 per trip. In contrast, transit trips by the general public cost, on the average, about 85 cents."

The report evaluated two alternatives to the DOT proposal: one called a Taxi Plan, which would emphasize on-call door-to-door service, and a another termed the Auto Plan, which would involve financial aid to disabled people so they could purchase specially equipped automobiles.

The taxi plan would cost $4.4 billion and serve 26 percent of the severley disabled, the CBO said. The auto plan would cost $6.4 billion and serve 30 percent of the severely disabled. Cost per trip for either alternative would be less than $8.

The problem with these alternatives, in the view of spokesmen for the disabled, is that the plans provide separate and not necessarily equal service. The matter is seen as a civil rights issue.

Transit authorities, speaking through the American Public Transit Association, have fought the propposed regulation on the grounds of added costs and increased inconvenience for regular patrons. A wheelchair lift, for example, adds about $20,000 to the cost of a bus. Furthermore, as riders in Washington have discovered, genuinely reliable lifts have yet to be developed.

Transportation Secretary Neil Goldschmidt has said he will reexamine the proposed regulations, with emphasis on the question of access to buses. A key assumption in those regulations was that Transbus, a low-floor ramp-equipped bus designed by a committee, would solve the problem. But U.S. manufacturers refused to build it.

In recent weeks, Goldschmidt has been talking instead about rehabilitating old buses and doing something to encourage bus manufactures to go forward with new production in confidence that federal regulations would not make their vehicles absolete.