 The PRT had three driverless Otis Hovair vehicles which had a hinged-window at each end for emergency exit.The concrete guideway was built as double track, connecting the three stations at Duke South, Duke North and Parking Garage II via a tunnel under Erwin Road.The 0.25-mile (<400 m) section between Duke South and Duke North was closed permanently on October 15, 2008 to allow for expansion of the hospital buildings.