Despite some vigorous opposition to their nominations, President Carter's choices to fill three places on the interstate commerce Commission are expected to get Senate confirmation.

The three, who are expected to support the recent trend of the ICC to relax federal regulation of surface transportation, are Marcus Alexis, chairman of the economics department of Northwestern University who would become the first black on the ICC in its 92-year history; Darius W. Gaskins Jr., an economist who has held a variety of government posts, the most recent being deputy assistant secretary of energy for policy analysis; and Thomas A. Trantum, a security analyst with Rothschild. Unterberg, Towbin in New York whose specialty has been regulated transportation.

After the confirmation hearing yesterday, Senate Commerce Committee Chairman Howard W. Cannon (D Nev.) said that based on what was heard, he "would expect they would get through the Senate" although he noted there were some "very powerful groups" against them. No executive committee session will be scheduled until after the Senate's July 4th recess, he noted.

At yesterday's hearing, representatives of the American Trucking Associations, a trucker's group called Assure Competitive Transportation, and the U.S. Labor Party opposed the nominations of the three, all contending that the nominees would be unable to support fully the existing laws that regulate surface transportation that are now under scrutiny by the Congress.

"Until Congress changes the law, you should not confirm anyone who doesn't believe in the present law and present policy," Edward V. Kiley, assistant to the president of ATA, said.

Although each of the three nominees has stated an overall preference for expanding the role of competition where feasible as a substitute for strict government regulation, they all told the committee yesterday they would not take actions as ICC members that would go beyond their authority as defined by policy statement and the law under which the ICC operates. Each also said, however, that it appears the law allows some flexibility to adjust regulations as economic conditions change.

"As I read the national transportation policy, I think it's quite flexible," Trantum said. Gaskins added that interpretations made by the ICC recently "do seem to make sense in the face of changing economic conditions and don't seem to strain the fabric of the law."

Alexis said that each case must be looked at individually. "One problem with regulation is it is cast in an earlier period and changing economic conditions may make them inappropriate or inefficient," he said, calling for continuous review.

Gaskins, in particular, underwent some strong questioning by Sen. John Warner (R-Va.) who said he had received a number of complaints about his nomination.

In an earlier hearing. ICC Chairman A. Daniel O'Neal told the committee that although the existing statute is flexible enough to permit many administrative reforms, it would like to see Congress enact legislation that would:

Create a general exemption authority to permit the ICC to exempt from regulation certain classes of truckers or trucking services, enabling the commission to remove regulatory restraints where it seems justified.

Codify the deregulatory initiatives the agency has already taken. All but one has been challenged in the courts.

Simplify ICC appellate procedures by limiting appeals to one per case; right now, the ICC has to hear an appeal each time a decision of the commission is modified or reversed. CAPTION: Picture, President Carter's three nominees for seats on the Interstate Commerce Commission face questioning from Senate Commerce Committee members. From left are Marcus Alexis, Thomas A. Trantum and Darius W. Gaskins Jr. By James K. W. Atherton - The Washington Post