Roll on-Roll off or Ro-Ro vessels come in many forms. They include vehicle ferries and cargo ships carrying truck trailers. The car carrier is the most commonly-used ro-ro vessels. These slab-sided vessels feature multiple vehicle decks comprising parking lanes, linked by internal ramps with access to shore provided by one or more loading ramp. Cargo capacity of such vessels is measured in Car Equivalent Units (CEU) and the largest car carriers afloat today have a capacity of over 6,000 CEU.