Unit train

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. 
They are distinct from wagonload trains, which comprise differing numbers of cars for various customers.
Unit trains enable railways to compete more effectively with road and internal waterway transport systems. Time and money is saved by avoiding the complexities and delays that would otherwise be involved with assembling and disassembling trains at rail yards near the origin and destination. Unit trains are particularly efficient and economical for high-volume commodities. Since they often carry only one commodity, cars are of all the same type; often the cars are identical.
Use.
Unit trains are typically used for the transportation of bulk goods. These can be solid substances such as:
Bulk liquids are transported in unit trains made up of tank cars, such as:
Food, such as:
Other examples include: