closure of the cover 2 of the subsurface system the described automatic hitching system between the automatic crane 18 of the collection truck 17 and the container with a closed base for emptying by turning is represented in fig8 the container is equipped on each side with a fixed arm 31 which at the upper extremity has a groove 32 enabling hitching to the outer element 28 of the coupling system 21 when the container 3 is removed from inside the underground bunker 4 a safety device covers the entirety of the opening of the underground bunker 4 in order to avoid accidental falls during collection the safety device remains concealed against one of the walls of the underground bunker 4 whenever the container 3 is located inside the underground bunker 4 when the container 3 is lifted for collection the device swings into the horizontal position covering the opening of the bunker 4 this safety device connected to one wall of the underground bunker 4 is equipped with the following elements to allow automatic positioning and shock absorption a rotating arm 35 a gas shock absorber 36 and a shock absorbing spring 34 when the safety device is in the horizontal position during collection of the container 3 there are two locks 37 located on the front wall of the bunker 4 which keep the device secure and stable when the container 3 is replaced inside the underground bunker 4 the locks 37 are released mechanically by means of two pedals 38 which are.