It is the only underwater vehicle tunnel currently in operation in the state, as the Baytown Tunnel was replaced in 1995 by the Fred Hartman Bridge. The tunnel consists of a single bore, 895 meters (2,909 feet) in length, with a six-percent roadway grade outward from the center towards each exit. Forced transverse ventilation is potentially provided by three automatic high-speed Westinghouse Sturtevant blower fans located in a tower at the north entrance. These fans are designed to keep the air free from high-levels of carbon monoxide.