Hopper wagon is a type of railway freight wagon used to transport loose bulk commodities such as coal , ore , grain , track ballast , and the like. Covered hopper wagons are used for cargo that must be protected from the elements (chiefly rain) such as grain, sugar, and fertilizer. Open hopper wagon are used for commodities such as coal, which can get wet and dry out with less harmful effect. Hopper wagon have been used by railways worldwide whenever automated cargo handling has been desired.