The Armstrong Tunnel has a pedestrian walkway on one side, and bicyclists find it easy to travel in the direction of the river due to the air draft through the tunnel.
The Armstrong Tunnel in Pittsburgh, Pennsylvania, connects Second Avenue at the South Tenth Street Bridge, under the Bluff where Duquesne University is located, to Forbes Avenue between Boyd Street and Chatham Square. It also has a pedestrian walkway on the western side. Pghbridges.com reports that since the air draft flows toward the river, bicyclists are able to travel through the tunnel in that direction "with little or no effort." 
