LHR PRT 6-21-10, T5, parking L2, from E at barrier to station platform, close-up of vehicle rear showing bumper and flat concrete guideway surface.  Vehicle depth beneath floor, approx. six inches.  This is ULTra PRT's biggest visible difference from the Chicago RTA/Raytheon PRT 2000 system of the 1990s.  PRT 2000's vehicles ran on three-to-four foot deep undercarriages, making its guideway considerably more complicated -- and expensive -- than the flat-surfaced platform depicted in these photos.