291 x 157 mm. A side view of a patrol train with ballast waggons and armoured pill box. The waggons in front of the locomotive were loaded with ballast which would trigger and absorb the explosive force of any mines laid on the track. Behind the locomotive was a small armoured pillbox truck manned by the security forces. These trains ran ahead of passenger trains and were in use from about 1949 until the introduction of Wickham Trollies the following year.