Hybrid rail

Hybrid rail, also known as diesel light rail transit (DLRT), is a mode of passenger rail service unique to North America that uses lightweight multiple unit trains—typically diesel multiple units (DMUs)—operating on the national rail system. In the United States, these vehicles do not comply with Federal Railroad Administration (FRA) Tier I crashworthiness standards and must operate under shared-use waivers that require temporal separation from freight rail traffic. Hybrid rail differs from conventional commuter rail by offering frequent, all-day service rather than being limited to peak-period operations. However, service frequencies are generally lower than those of urban light rail systems. Although often categorized as a subset of light rail, hybrid rail systems employ mainline railway infrastructure and are closer in function to tram-train, railcar or former interurban operations.

The first hybrid rail system in North America was New Jersey Transit's River Line, which began service in 2004. Since then, similar systems have been introduced in other regions. Hybrid rail aims to deliver rail transit service without the capital costs associated with electrification or fully dedicated rights-of-way. Some systems, such as Ottawa’s O-Train Line 2, have transitioned to regional rail or been discontinued, such as the Puebla–Cholula Tourist Train in Mexico. Several expansions of existing hybrid rail services are currently planned or under development in the United States.