Acronym for Reseau Express Regionale, the RER is part of Paris' commuter rail system, falling between the regional commuter trains and the Metro. The RER is run jointly by the SNCF and RATP and has five lines, lettered A through E, and covers a large portion of the Ile-de-France:

  • Line A runs roughly east-west between Disneyland Paris and the city's western banlieue;
  • Line B runs northeast-southwest and connects Paris' two major airports, Charles de Gaulle Airport and Orly Airport;
  • Line C spiders all over the region in eight different arms, following the Seine through Paris and going to the Chateau de Versailles, among other places;
  • Line D runs north-south and is used primarily by commuters;
  • Line E originates near the Opera Garnier and serves several eastern banlieue.

While Line C can be slow at times, the RER is generally the fastest way to travel between distant points in Paris. As an added bonus, it is much les used by tourists, since there are fewer stops and the system is deeper in the ground than the Metro; thus, there are fewer crowds and pickpockets than there are on the Metro. RER trains generally run at higher speeds than the Metro, as well.