Secretary of Transportation Elizabeth Hanford Dole is actively promoting automobile air bags while the government is preparing to fight in the Supreme Court against their mandatory installation in new cars.

The air bag is a good safety device, Dole said, and the Department of Transportation will encourage "market incentives" to promote it in coming months.

Her comments came in an interview last week on several transportation topics two months after she was sworn in as DOT's eighth secretary.

Dole endorsed air bags and listed several ways DOT is planning to promote their use but, because the issue is to be argued at the Supreme Court on April 16, she declined to comment on the Reagan administration's opposition to requiring them.

She said DOT will provide air bags for 5,000 new government-purchased autos and hopes to refit about 500 state police cars with air bags for the driver's side only. "These are activities I can be pushing right now to get those market incentives," she said. The hope is to encourage manufacturers to offer air bags and encourage automobile owners to buy them as an option.

One of the Reagan administration's first acts threw out the Carter administration mandate on air bags, which were to have been required on new cars beginning with the 1982 model year. A federal district court overturned the administration's move, and the issue has gone to the Supreme Court.

Asked if she is comfortable with the administration's position on air bags, Dole said that because the case is to be argued before the Supreme Court she is "not comfortable discussing it." Asked if she thinks the bag is a good idea, she said, "Yes, I do, I do."

Transportation safety, Dole said, will receive major emphasis. She has given substantial time and support to the growing nationwide campaign to force drunken drivers off the highways and has pledged federal action in dealing with drunkenness among railroad employes.

Dole also said:

* DOT is pledged to provide federal financing for 75 miles of Washington's planned 101-mile Metro system, but she does not see a commitment beyond that. Hers is a somewhat firmer restatement of a Reagan administration position first staked out by former secretary Drew Lewis.

* New federal regulations requiring states to accept double-trailer trucks on interstate and some other primary highways will be enforced by the federal government through injunctions, if necessary. Some states have said they will not permit longer trucks. "We are going to try and work it out with a state first . . . ," she said. "However, we are responsible for enforcing this and, if that appears not to work out, then we'll have to go forward with the injunctions."

* The administration has abandoned early elimination of the Civil Aeronautics Board. The CAB, which regulated routes and fares in domestic aviation for many years, is scheduled to perish Jan. 1, 1985, with its remaining domestic and international aviation functions to be transferred to DOT. "I never have felt that we should really pursue early elimination ," she said. "I think we have things that have to be ironed out."

* The administration has not developed a firm position on what to do with the remnants of shrinking regulatory agencies. Sen. Bob Packwood (R-Ore.) has proposed a single "superagency" that would acquire what is left of the CAB, the Interstate Commerce Commission and the Federal Maritime Commission. "The first thing we've got to do is identify what the residual functions ought to be," Dole said. "Then I think your organizational structure follows . . . ."

* DOT is vigorously pursuing sale of Conrail, the federally owned northeastern freight railroad. Dole, who has met with the investment banking firm of Goldman Sachs & Co., said, "They will be talking with a number of possible buyers in the private sector. There's a possibility of a public offering if that does not materialize."

* She has heard anguished complaints of local transit officials and some congressmen about proposed cuts in operating assistance for local transit systems. Nonetheless, she said:

"The philosophy of this administration is that operating subsidy levels are the kinds of decisions best made at the local level, whether the issue is fares or the extension of service or management. The federal government is distorting the collective bargaining process" by providing money that can be used for bus drivers' and mechanics' salaries and that "is just not beneficent. It's produced uneconomic decisions . . . ."

* The administration is still seeking to develop legislation to establish "user fees" to pay for dredging ocean ports. For three years, small and large ports have battled about the most equitable way to pay, while the Office of Management and Budget has pushed for 100 percent cost recovery of a function performed at taxpayer expense since the beginning of the Republic. "With this country's potential for being a leading coal exporting country, those deep water ports are so important . . . ," she said.

* Urban Mass Transportation Administrator Arthur E. Teele Jr. will probably leave in the near future. "I think he looked at his stint as one that would not be a long term but rather two years plus," she said.

Federal Railroad Administrator Robert W. Blanchette has resigned effective May 1. Dole said she does not expect changes in the Federal Aviation, Federal Highway and National Highway Traffic Safety administrations.

Dole, White House assistant for public liaison before moving to DOT, has been concentrating on learning the intricacies of these and other issues while visiting many DOT facilities around the country and burnishing her contacts on Capitol Hill, especially with important House committees.

"The Senate I know well," she said, an understatement recognizing the fact that her husband is Sen. Robert J. Dole (R-Kan.), chairman of the Senate Finance Committee.