Marvin L. Fair, 86, a professor emeritus of economics at American University and a specialist in transportation and public utilities, died of congestive heart failure Aug. 25 at Montgomery General Hospital.

Dr. Fair, who lived in Sandy Spring, was born in Cameron, W.Va. He graduated from Ohio University and took master's and doctoral degrees in economics at Ohio State University. He did further work in economic history and theory at Harvard University.

Dr. Fair was a professor of transportation economics at the Temple University business school from 1932 to 1946. He was a professor of economics and chairman of the Institute on Foreign Transportation at Tulane University from 1947 to 1958. He then moved to the Washington area and joined the faculty at American, where he headed a special program on transportation for business executives. He retired as professor emeritus in 1972.

During World War II, Dr. Fair was chief consultant on transportation to the War Production Board. He later was chief of the port development section of the U.S. Maritime Commission. He also served as a consultant to the Brookings Institution on an report on transportation for the Hoover Commission, to the undersecretary of Commerce for transportation and to the Organization for European Economic Cooperation.

He was the author of numerous articles and books in his field. He was a member of the American Economic Association, the American Society of Traffic and Transportation, the Cosmos Club and the Sandy Spring Friends Meeting.

Survivors include his wife, Rachel P. of Sandy Spring; two children, Mary E. McConnell of Tucson, Ariz. and Harlan W. of Chappaqua, N.Y.; and seven grandchildren.