Harold William "Bill" Merritt Jr., 73, a retired Navy commander and former Department of Transportation official who studied urban mass transportation problems, died May 2 at Pentagon City Hospital of complications resulting from injuries sustained in a car accident in March at Reagan National Airport.

Airport police said Mr. Merritt apparently lost control of his car at a departure ramp in front of a terminal. His car struck another vehicle before jumping the curb and hitting an air vent.

Born in Twin Falls, Idaho, he was the son of science and math teachers. He attended the University of Washington but later transferred and received an undergraduate degree in applied science civil engineering from what is now Case Western Reserve University.

Mr. Merritt also received a master's degree in civil engineering from Rensselaer Polytechnic Institute.

Until his military retirement in 1967, he served 20 years in the Navy Civil Engineer Corps. At the start of his career, he was assigned to the 53rd Naval Construction Battalion and was stationed on Bikini Atoll.

He later was involved in the construction of encampments and other structures.

After the Navy, he briefly worked for the Department of Housing and Urban Development as director of a study looking into new systems of urban transportation. He then worked a few years at the Department of Transportation, where, among other things, he oversaw management of a $25 million program to design, develop and test a 150-mph tracked, levitated, 50-passenger vehicle system.

In 1973, he was presented with the Secretary of Transportation Award.

In retirement, he became director of the National Bonsai Foundation and served as chairman of the foundation's building committee. In those capacities, he was involved in the completion of the National Bonsai and Penjing Museum at the U.S. National Arboretum.

Survivors include his wife of 54 years, Norma Merritt of Arlington; four children, Mark G. Merritt of Richmond, Scott W. Merritt of Munich, W. Todd Merritt of California and Catherine M. Hauer of Andover, Mass; a sister; and eight grandchildren.