Wiktionary
n. (context rail transport English) a purpose-built railway vehicle that allows the driver to operate a locomotive at the opposite end of a train.
Wikipedia
A Driving Van Trailer (DVT) is a purpose-built railway vehicle that allows the driver to operate a locomotive at the opposite end of a train. Trains operating with a DVT therefore do not require the locomotive to be moved around to the other end of the train at terminal stations. Unlike many other control cars, DVTs resemble locomotives (specifically Class 91) and thus when the train is operating in "push" mode it does not appear to be travelling backwards. The vehicles have no passenger accommodation due to rules in place at the time of building that prohibited passengers in the leading vehicles of trains that travel at more than .