RER

plural RERs

1. A type of railway system that generally runs from suburbs or satellite towns into a city centre, with a central tunnel or overground corridor with higher speeds and more widely spread stations than a subway or metro.

   Reinvented according to this model—called regional express rail (RER)—Metra's key hubs would be O'Hare Airport, the Loop, and McCormick Place.

   2021 November 10, “A path to high-speed rail in Chicago—through a reinvented Metra”, in Chicago Business

   1 more example

   […] the recently approved Crossrail link, together with the existing Thameslink, constitute the basis of an RER for London, which by the end of this decade will provide a single system, linking Reading with Colchester and Cambridge[…]

   1991, Working Paper

plural RERs

1. Any of many RER systems in French-speaking countries.
2. GO Expansion, a project to improve commuter rail in Ontario.

   GO Transit also uses some tunnels in the city. Its Metrolinx RER programme includes laying 150km (93 miles) of new track, and some of this, for example under Highways 401 and 409, will be in tunnel.

   2020 September 8, Mark Ovenden, Underground Cities: Mapping the tunnels, transits and networks underneath our feet, Frances Lincoln, →ISBN, page 42