Buses exiting 3rd Street Tunnel

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A typical early morning platoon of transit buses exiting the Third Street Tunnel through Bunker Hill in downtown Los Angeles, taken in December 1979. These buses, supplied and operated by the Southern California Rapid Transit District, were used as the carefully-controlled traffic to induce air flow through the tunnel. With the cooperation of the Los Angeles Street Maintenance and Police Departments, these tests were run to make measurements inside the tunnel and beyond the exit in order to define the air flow characteristics. The results will be used in the design of partially-covered, depressed freeways which have no mechanical ventilation. Participating are the Federal Highway Adm. and Jet Propulsion Lab. Note the test director, Bain Dayman, in the yellow jacket pushing his bicycle, made necessary due to the one-way tunnel restriction.