A unit train, also called a block train or a trainload service, is a train in which all cars (wagons) carry the same commodity and are shipped from the same origin to the same destination, without being split up or stored en route. This saves time and money, as well as the hassle, delays and confusion associated with assembling and disassembling trains at rail yards near the origin and destination. It also enables railways to compete more effectively with road and internal waterway transport systems, However, unit trains are economical only for high-volume customers. Since unit trains often carry only one commodity, cars are of all the same type, and sometimes the cars are all identical apart from possible variations in livery.