Rolling stock is the fleet of all the wheeled vehicles owned by a railroad or government that can be rolled on railroad tracks. In some countries, like the United States, this definition includes powered vehicles, like locomotives. Some other countries, however, such as the United Kingdom, deliberately segregate the two, with locomotives and other powered vehicles termed running stock or motive power. Outside the railroad industry, some companies use the term to mean any wheeled, easily transportable vehicle, such as a truck or automobile.
Other than locomotives and other powered cars, there are four main types of railroad rolling stock. The two revenue producing cars, freight and passenger, are by far the most numerous. Freight cars are designed for all manner of contents, whether boxed or loose, solid, liquid or gas. The boxcar, essentially a very large box set upon wheels and secured by sliding doors, is the most common of all freight cars. Some other freight cars are generic in nature and can haul a wide variety of goods, while others have been specially designed for a single purpose, such as carrying automobiles or airplane parts.
Passenger cars are the other revenue producing cars. These also are produced in a number of different styles, usually based on their intended use. Those passenger cars built for long journeys, for example, have fewer seats and are generally more comfortable than the cars built for commuter trains, where rides of over 90 minutes are uncommon. Specialty passenger cars used on long journeys include meal cars, which are like restaurants on wheels, and observation cars, designed to enhance passengers’ ability to appreciate the scenery while traveling. Sleeper cars with individual passenger compartments that can be converted to bedrooms are useful for even longer journeys.
The other two types of non-powered rolling stock don’t produce any revenue for the railroad. These include cars used by the railroad itself, and cars specially built for military use. Among the railroad’s non-revenue cars are cabooses and roughly a dozen or so other types of specialized cars built for such tasks as maintaining the right of way, housing railroad workers or offices, and railroad cranes. Military cars include any of a number of specialized cars built for military operations on railroad tracks. They were a fairly common sight in Europe during the 20th century, with perhaps their most famous and controversial use being to move nuclear weapons around to make it difficult for other nations to target them in a first strike.
All railroad cars are built according to industry standards, can be run on all tracks and be connected to each other regardless of type or which railroad they belong to. From a financial perspective, a railroad’s rolling stock is considered almost liquid in nature, and is frequently pledged as collateral for loans. This makes keeping track of rolling stock a critical function for any railroad.