Escape Adits for Tunnel Safety

The Upper Narrows Tunnel on Highway 160 in southern Colorado has been designed with a unique system of escape adits to provide for life safety in the event of emergencies in the tunnel. The use of adits provides for a higher level of safety in this application than would be provided by the more common ventilation system. A summary of the unique project conditions that facilitate such a system is presented, and the methods of analyses and results of calculations used during the design are reviewed.