What pivots on a transverse axis provided by pins allowing the tug to pitch independently from the barge?

The articulated tug and barge unit (ATB) is specifically designed to allow for independent motion between the tug and the barge. This is achieved through a unique coupling system that includes pins and a pivoting mechanism, which provides a transverse axis. This allows the tug to pitch and maneuver separately from the barge, enhancing the overall maneuverability and control when navigating through various conditions.

This design is particularly beneficial in rough waters or when precise movements are required, as it enables the tug to respond to the sea conditions without transferring those movements directly to the barge. Thus, the ATB can maintain better stability and performance, making it a preferred choice for towing and transporting cargo over water.

Other types of tugs, like conventional tugs and push tugs, typically do not have this capability to pitch independently due to their fixed connections to the barges they tow or push. Hybrid tugs may incorporate some advanced features but do not specifically utilize the pinned transverse axis structure of the ATB for independent pitching.