It is called a RO-RO shipment that is made through a ship that carries wheeled cargo, such as cars, trucks ...
The boats have ramps built on the ship itself or fixed on the ground so that loading on wheels is much easier what to do with a crane.
The wheeled cargo accesses the boat through a sluice either in the stern or in the bow. There is also the cars-carriers
which is a square transport model intended for loading and unloading only cars.