A car float is a type of barge with railroad tracks mounted to its deck to allow railroad cars to be placed on that deck. The car float can then be floated across a waterway to transport the railroad cars to another location. The car float is almost always an unpowered boat, which means it must be towed or pushed by another boat. A tugboat is often used to pull the barge across a waterway, or a towboat can push it instead. The size of the float will vary according to its purpose and the frequency with which it is used.
A train ferry is very similar to a car float in terms of purpose, but design and propulsion differ significantly between the two crafts. A car float is a barge designed for river use, which means the float is a flat-bottomed vessel. It features no engines or propulsion systems of its own in most cases, so it must be used in conjunction with another ship. Train ferries feature the same roll on, roll off convenience of a car float, but this ship is often self-propelled and is not flat-bottomed, meaning it can be navigated in open water, though it may be limited in movement through shallow-bottomed rivers.
Before the advent of on-road trucking, the car float system was commonly used throughout many regions of the world in which rail travel could be limited by waterways. New York City, for example, is situated between rivers, making rail freight transport difficult in some instances. To counteract this inefficiency, car floats were used across the Hudson river daily to transport rail cars quickly throughout the area. Once truck travel became more common and the trucks became capable of carrying heavier loads, car floats were used much less, though they are still the best choice for certain applications.
Cars are loaded onto a car float using a specially designed ferry slip with an apron that features railroad tracks. The apron raises and lowers in accordance with the water level and the position of the vessel in the water, and rail cars can be transported over the rails mounted on the apron directly onto the ship. This makes for a quick and easy loading an unloading process, further enhancing the efficiency of this method of transport. The apron may be operated electronically, with a pulley system, or using a counterweight system that ensures the apron stays in proper position during loading and unloading.