A dividing baffle (21) delimits in a loading hopper (5) a first and a second chamber (5a,5b), consecutively set side by side away from a body (4) of a vehicle (2). The dividing baffle, able to collimate at the top with a dividing wall of a container upset above the hopper (5), presents a lower edge (21a) movable vertically to open and shut communication between the collection chambers (5a, 5b). A first waste received in the first chamber (5a) falls onto a fixed bottom (11) to be transferred into a lower compartment (4a) of the body (4). A second waste received in the second chamber (5b) is transferred into an upper compartment (4b) of the body (4) after a movable bottom (16) is distended in the hopper (5) and the lower edge (21a) is raised to allow the passage of a thruster (14) underneath the dividing baffle (21).