Tracked Ambulance: -
Owing to the fact that small wheels have a bad cross-country performanse, a tracked ambulance was developed employing bogie wheels and a track of standard pattern
The frame of the amulance supports a turntabe on which is mounted an "I" beam. at each end of the beam is a crutch, adjustable in height, which is clamped onto the axle of the casualty.
From a REME training guide available
http://www.aecmilitant.co.uk/index2.html on the downloads page