Rod Diridon worked as a carpenter and railroader during vacations to pay for his education at San Jose State University (BS in accounting in 1961, MSBA in 1963). He was active in student government and was a precinct coordinator for the 1960 Kennedy presidential campaign. He completed two combat tours as a naval officer in Vietnam. Returning in 1967, he completed the executive development program at the Lockheed Missiles and Space Company, leaving in 1969 to found the Diridon Research Corporation (now the Decision Research Institute).

He wrote legislation for Senator Alquist's Joint Committee on Seismic Safety. Diridon turned to community activities, chairing over 100 local, state, and national efforts. Though many of those were associated with transit, he was also president of the San Jose Symphony Association, YMCA, San Jose Jaycees and National Council on Alcoholism.

In 1972, Diridon was elected to the Saratoga City Council and was recognized as one of the Ten Outstanding Young Men of America. Two years later, he upset incumbent Supervisor Ralph Mehrkens at the polls. Supervisor Diridon took on transportation as his issue.

Throughout his 20 years on the Santa Clara County Board of Supervisors, Diridon. co-chaired the early Parks Charter Measures, created the Los Gatos Creek Trail Board and was an ardent environmentalist. A most proponent of public transportation, Diridon is considered the “father of modern transit” in Santa Clara County and credited with countless achievements including building the light rail system. The main train station in San Jose was renamed "The Diridon Station" in his honor. Diridon is the only person to have chaired the San Francisco Bay Area’s three regional governments: the Metropolitan Transportation Commission, the Bay Area Air Quality Management District, and the Association of Bay Area Governments.

Diridon retired from political service due to term limits in 1995 after completing six terms as chair of both the Santa Clara County Board of Supervisors and the Transit Board. He went on to serve as the Executive Director of the Mineta Transportation Institute and found the non­profit San Jose Trolley Corporation (now the California Trolley and Railroad Corporation), which works to restore historic trolleys.