The River Line is a hybrid rail line in southern New Jersey that connects the cities of Camden and Trenton, New Jersey's capital. It is so named because its route between the two cities is parallel to the Delaware River.

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 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. All of the systems use similar technologies, and some systems blur the lines between the different forms.