car

A railroad car, also known as a freight car, is a vehicle designed to transport cargo on a railroad. Early freight cars were primarily made of wood, but by the late 1800s, all-steel cars became dominant due to their durability.12

Modern freight cars have evolved from three basic types:
* Open-top cars: These include gondola and hopper cars. Hopper cars are used for bulk materials like coal and grain, featuring hatches for easy unloading. Gondola cars have fixed bottoms and are unloaded from above, used for manufactured goods.2
* Boxcars: These are enclosed cars with sliding doors, designed to protect goods from weather and theft. Variations include refrigerator cars for perishable items and stock cars for livestock.2
* Flatcars: These are used for heavy machinery and military equipment. Innovations include specialized flatcars for containers, truck trailers ("piggyback cars"), and new automobiles.2

Other specialized cars include tank cars for liquids and rack cars for vehicles. Design differences exist between North America and Europe due to varying economic and technological factors, with a global trend towards maximizing payload capacity and efficiency.23