Riggs National Bank has promoted James D. M. McComas to the position of executive vice president. McComas, who heads the bank's international division, has been a senior vice president at Riggs since 1976. Previously, he was an executive with W. R. Grace.

Robert J. Derby will resign his position as director of personnel of The Washington Post on Oct. 1 to become senior vice president of human resources of the First National Bank of Oregon.

Derby came to The Post in 1971 as assistant director of employe relations, becoming director in 1974. Before that he had been manager of employe relations for International Harvester Co.

Charles W. Handy Jr. has been promoted to senior vice president and branch administrator of Perpetual Federal Savings and Loan Association.Handy was serving as vice president and branch administrator. He has been with Perpetual for 35 years and managed three branch offices before assuming his position as branch administrator.

J. Frank Shoaf was elected chairman of the board and Anne F. Douglass was named president of Kennedy Bank of Bethesda.

Shoaf is senior vice president of the L. G. Balfour Co. and was a member of Kennedy's board. Douglass has been with the bank three and a half years and has been vice president and a member of the board.

John A. O'Connor Jr. has been elected senior president and secretary of the corporation and Donald J. Trufant has been named senior vice president in the banking division of Mercantile-Safe Deposit and Trust Co. of Baltimore.

O'Connor came to Mercantile in 1970 from the law firm of Frank, Bernstein, Conaway and Goldman, where he was a partner, to become the bank's corporate secretary. He served as Assistant State's Attorney of Baltimore City from 1956 to 1959.

Trufant joined the bank in 1973 after serving the Commercial Credit Equipment Corp. as director of corporation aircraft sales.

Paul H. Reistrup, former president and chief executive officer of Amtrak, has been elected vice president of R. L. Banks and Associats Inc., a Washington transportation analysis firm. Reistrap, who headed Amtrak from 1975 until May of this year, played a key role in establishing the railroad's ownership of the Northeast Corridor and in administering Amtrak's role in the $1.8 billion Northeast Corridor Improvement Program.