I saw this T.I.P. trailer in a warehouse parking lot as I was driving by, so I drove in for a close shot. Its doors were open (to air it out?). If one looks closely at the back end of the trailer one can see the shiny interior surface of the door, which is in the open position and tethered to the trailer's outside wall.
Drivers in England who leave a trailer parked often leave the doors open to show thieves that there is no point in breaking in because the trailer, or lorry is empty. Of course thieves now don't have to go looking for trailers with valuable goods in, they are the ones with the doors locked.
