Smaller railroads like these are called short line railroads, and they play an important role in the U.S. freight shipping network.

A small railway is most commonly referred to as a narrow-gauge railway. This term applies to any railroad where the distance between the two tracks (the gauge) is narrower than the "standard gauge" of 1,435 mm (4 ft 8.5 in). Within this category, even smaller versions are often called miniature railways or ride-on railways, which are frequently found in parks or private estates. In a more technical or historical context, you might hear the term light rail, which refers to urban transit systems that use smaller, lighter equipment than heavy freight trains. In specific geographic regions, they are known as heritage railways or "toy trains," such as the famous Darjeeling Himalayan Railway in India. These smaller systems were historically built because they are much cheaper to construct in mountainous or difficult terrain where tight curves are required, making them a charming and vital part of global rail history and modern tourist attractions.