Commuter rail

Clockwise from top left:

A Metra service of double-decker cars hauled by an F40PH in Chicago
A RER NG train on line E of the Réseau Express Régional in Paris
A CPTM train on the Coral Line in São Paulo
A Treno Servizio Regionale train in Milan
An AM class electric multiple unit used in Auckland
Two N1000 series EMUs of the Keikyu railway pass each other in Tokyo

Commuter rail or suburban rail is a passenger rail service that primarily operates within a metropolitan area, connecting commuters to a central city from adjacent suburbs or commuter towns. Commuter rail systems can use locomotive-hauled trains or multiple units, using electric or diesel propulsion. Distance charges or zone pricing may be used.

The term can refer to systems with a wide variety of different features and service frequencies, but is often used in contrast to rapid transit or light rail.

Some services share similarities with both commuter rail and high-frequency rapid transit; examples include German S-Bahn in some cities, the Réseau Express Régional (RER) in Paris, the S Lines in Milan, many Japanese commuter systems, the East Rail line in Hong Kong, and some Australasian suburban networks, such as Sydney Trains. Many commuter rail systems share tracks with other passenger services and freight.

In North America, commuter rail sometimes refers only to systems that primarily operate during rush hour and offer little to no service for the rest of the day, with regional rail being used to refer to systems that offer all-day service.