Memoranda, correspondence, meeting minutes, maps, blueprints, newspaper clippings and presentational material concerning various traffic control topics and traffic and transportation planning. General topics include traffic planning, street closures, civil defense, traffic safety, and traffic control; specific subjects include Central Business District Exclusive Bus Lanes, METRO, the Seattle Transit System, New Deal traffic projects, and World War II traffic routing. The bulk of the material dates from the New Deal and World War II periods.

A large portion of the series encompasses the records of J.W.A. "Arch" Bollong who served as Traffic Engineer from 1930 to 1952. The records reflect major street and bridge construction projects during that period including Alaskan Way, Aurora Avenue, the Aurora Bridge, and traffic issues related to the Lake Washington Floating Bridge, Boeing Company expansion, and the Seattle Transit System. Traffic safety became a major concern as more and more automobiles were introduced to Seattle. Records include discussions of school crossing issues, activities of the Seattle Traffic and Safety Council, and local and national safety contests.

The largest body of records relate to Civil Defense, particularly to the location of air raid sirens and whistles, lighting regulations during blackouts, traffic and danger signals used during blackouts, and the creation of traffic routes during wartime. The latter included identifying routes through the city that would be used by the military in an emergency as well as the routing of normal traffic.

Most of the records that post-date Bollong's tenure as traffic engineer are related to the controversy around the proposed creation of exclusive bus lanes in the Central Business District in the mid-1970s.