Narrow gauge railroads have a distance of 3 ft. 6 inches or less between the rails (1067 mm). Narrow gauge is less expensive to build than Standard Gauge and can be built to track smaller radius curves, which makes these railroads particularly useful in mountainous terrains. This gauge was often used for local industry, logging, mining, or quarrying.
Standard gauge railroads are built with 4 ft 8 ½ inches between the rails (1435mm). Their wider track allows greater stability which means more haulage capacity at higher speeds. Standard gauge was created in an effort to allow easier movement of trains between countries and to allow for standardized equipment to be manufactured. Today about 60% of the world’s trains use standard gauge.
Model rail clubs will often define themselves by the gauge of railway their members model. Most clubs define themselves as Narrow gauge, Standard Gauge, or Off-Scale, where the track is not scaled true to size (such as in O scale railways).
Some early Lionel model trains in the United States were sold as a trademarked Standard Gauge with a gauge of 2 1/8 inches (54 mm) between the outer rails, but this gauge was discontinued in the 1940’s.