Integrated Tug Barge (ITB)

An integrated tug-barge (ITB) is a tug-and-barge combination locked together so rigidly that the two hulls behave as one ship, with no relative motion in any plane. The tug fits snugly into a deep notch in the barge stern and is pinned or bolted into a fixed connection, unlike the hinged articulated tug-barge that pitches freely. The Great Lakes vessel Presque Isle is a well-known ITB. The rigid link gives ship-like seakeeping and speed but transfers full hull-girder loads across the joint, so ITBs need heavier structure and were largely overtaken by ATBs, which crew as a tug yet ride a seaway through the hinge.