Since the mid-nineteenth century, model trains have allowed ordinary people to operate their own railroad system. Hobbyists could run their own small tracks and watch their models slide along the rails when electric train sets arrived on the scene. Model train sets have evolved over time, and scale models are now available in a variety of sizes. Hobbyists can design their own scenery, organize their own train yards, and connect their own cars to create an elaborate or simple train set.
Model train sets are available in a variety of scales, or sizes, and are based on actual train cars. The resemblance is now much more accurate than it was decades ago. G scale, HO scale, and N scale are the most common scales. These represent various ratios; in the HO scale, for example, 3.5 mm equals approximately one real foot. To propel the engine, the model train travels on metal rails that are charged with direct current. A conductor can change the voltage or polarity to control the speed or reverse the direction.
When hobbyists began to value realism over the inaccuracy of toy trains in the 1950s, model train sets became popular in the United States. Because it allowed for a realistic look while also allowing the hobbyist to create a train set in a smaller space, HO scale became the most popular scale. In the United States, HO trains are the most widely available, and accessories such as scenery and buildings are cheaper and easier to come by in this scale.
Hobbyists have begun to customize their model train layouts to reflect a specific era or location. A layout could, for example, be based on a real-life railroad, such as the New Haven line in Connecticut and New York, or the Santa Fe line in the southwest United States. More dedicated hobbyists will strive for realism, and will make every effort to ensure that their layouts are free of anomalies, such as a modern automobile driving down the street of a 1950s layout. Several publications are available on newsstands to assist hobbyists in determining which model train is best for them and which layout will best suit their needs.