Light rail in the United States

Light rail is a mode of rail-based transport, usually urban in nature. When compared to heavy rail systems like commuter rail or rapid transit (subway), light rail systems are typically designed to carry fewer passengers and are capable of operating in mixed traffic (street running) or on routes that are not entirely grade-separated. Systems typically take one of four forms: the "first-generation" legacy systems, the "second-generation" modern light rail systems, streetcars, and hybrid rail systems (light rail with some commuter rail features). All of the systems use similar technologies, and some systems blur the lines between the different forms.

The United States, with its 27 systems (as counted by the Light Rail Transit Association), has a much larger number of "true" light rail systems (not including streetcar systems), by far, compared to any other country in the world (the next largest are Germany with 10 and Japan with 9).^[1]

According to the American Public Transportation Association, of the roughly 30 cities with light rail systems in the United States, the light rail systems in six of them (Boston, Los Angeles, Philadelphia, Portland (Oregon), San Diego, and San Francisco) achieve more than 30 million unlinked passenger transits per year.^[2]