The hopper car has an open top. The bottom of the car can be opened to unload the freight. This model has been around since the late 1820s, when it was used mainly to carry coal, according to the American-Rails website. Original hopper cars were made from wood. Later models had a wood-steel construction, and modern cars are made of steel only. Modern hopper cars still carry coal, but can also carry iron or crushed rock.
Tanker cars can be identified by their cylindrical shape. These cars are used to haul liquid commodities. They became more popular at the beginning of the 20th century as liquid food commodities, such as vegetable oils and corn syrups, became mainstream. Tanker trucks are also used to carry chemicals or fuels. A placard on the lower right side of the car describes the contents and whether or not they are hazardous.
Named for its boxy, rectangular shape, the boxcar is the most common and most recognized rail freight car. Boxcars can carry any type of non-bulk freight, from packaged food to boxed fuels. The advantage of the boxcar is its enclosure, which keeps contents protected from rain or other hazards. Boxcars can also be insulated or refrigerated.
The gondola car is often mistaken for the hopper car due to its open top, but it is actually more closely related to the flatbed car. The gondola usually does not have the bottom hatch release of the hopper, and sits much closer to the ground. Gondola cars carry a range of freight, including wood chips, scrap metal and coal. Some models have tops that flip closed to protect freight from bad weather.
The flat car was the original railroad freight car. Its flat, open platforms can carry large freight that would not fit in a car with walls. Flat cars can carry boulders, logs, steel beams and iron rails. The freight is typically stacked and secured with chains for transport.
