Traffic descending upon the Liberty tunnels
The Liberty Tunnel, or "Liberty Tubes", as they are known locally, were built in 1924. The Tunnels which have a total length of 5,889 feet, helped alleviate the problem of motorists going over or around Mount Washington to get to the South Hills suburb of Pittsburgh. The boring was completed in July 1922. By January 1924 the tunnels were substantially complete and opened to traffic. Officers counted the number of vehicles entering the hours of use were limited to keep the exhaust gases from building to dangerous levels. In 1928 a mechanical plant with four tall stacks was built over the center of the Tubes to draw exhaust and provide a constant supply of fresh air. Four years after the completion of the Tubes, the Liberty Bridge was completed, opening on March 27, 1928. The Tubes carried approximately 25,000 vehicles in 1932 and in 2000; the daily average traffic was 63,027 vehicles.