A fifth wheel coupling assembly for a piggyback wagon, comprising: a fifth wheel plate with an upper face (12.1) and a lower face (12.2) opposite the upper face, and comprising a receptacle configured to receive a trailer king pin, said receptacle preferably being a cylindrical receptacle extending from the lower face (12.2) side and opening out in the upper face (12.1) of the fifth wheel plate; a locking device capable of locking the king pin in the receptacle; a follower element arranged in the receptacle, said element being displaced by the king pin introduced into the receptacle from a rest position into an engaged position; and an indicator element joined mechanically to the follower element, so as to move between a first and a second position corresponding respectively to the rest position and to the engaged position of the follower element; said fifth wheel coupling assembly further comprising: a first sensor associated with the follower element, the first sensor being a contact sensor arranged so as to be actuated when the follower element is in the engaged position; a second sensor arranged to detect a locking position of the locking device, the second sensor being a contact sensor; a third sensor capable of detecting the presence of a container or a semi-trailer in the vicinity of the fifth wheel, the third sensor being a distance sensor; and a control unit configured to receive signals from each of the sensors (70, 72, 74) and to determine the fifth wheel coupling status on the basis of these signals, in particular a "loaded" status. a fifth wheel plate with an upper face (12.1) and a lower face (12.2) opposite the upper face, and comprising a receptacle configured to receive a trailer king pin, said receptacle preferably being a cylindrical receptacle extending from the lower face (12.2) side and opening out in the upper face (12.1) of the fifth wheel plate; a locking device capable of locking the king pin in the receptacle; a follower element arranged in the receptacle, said element being displaced by the king pin introduced into the receptacle from a rest position into an engaged position; and an indicator element joined mechanically to the follower element, so as to move between a first and a second position corresponding respectively to the rest position and to the engaged position of the follower element; said fifth wheel coupling assembly further comprising: a first sensor associated with the follower element, the first sensor being a contact sensor arranged so as to be actuated when the follower element is in the engaged position; a second sensor arranged to detect a locking position of the locking device, the second sensor being a contact sensor; a third sensor capable of detecting the presence of a container or a semi-trailer in the vicinity of the fifth wheel, the third sensor being a distance sensor; and a control unit configured to receive signals from each of the sensors (70, 72, 74) and to determine the fifth wheel coupling status on the basis of these signals, in particular a "loaded" status. a first sensor associated with the follower element, the first sensor being a contact sensor arranged so as to be actuated when the follower element is in the engaged position; a second sensor arranged to detect a locking position of the locking device, the second sensor being a contact sensor; a third sensor capable of detecting the presence of a container or a semi-trailer in the vicinity of the fifth wheel, the third sensor being a distance sensor; and a control unit configured to receive signals from each of the sensors (70, 72, 74) and to determine the fifth wheel coupling status on the basis of these signals, in particular a "loaded" status.