(1) When a police escort travels in a prison van or in a separate compartment to that occupied by the prisoners, two Constables shall be placed on sentry duty over the prisoners, being relieved every two hours. (2) At every station where the trains stops fifteen or more minutes, the officer commanding the escort shall personally test the window fastenings, see the prisoners are not suffering in health, and arrange for any necessary cleaning of the carriage and the refilling of water tanks and supply of drinking water to the prisoners.