The RER (French pronunciation: [ɛʁəɛʁ]; French: Réseau Express Régional, "Regional Express Network") is a rapid transit system in France serving Paris and its suburbs. The RER is an integration of a modern city-centre underground rail and a pre-existing set of commuter rail lines. It has several connections with the Paris Métro within the city of Paris. Within the city, the RER functions like the Métro, but is faster as it has fewer stops. Since 1999 the network has consisted of five lines: A, B, C, D and E. The RER is still expanding: Line E, which opened in 1999, is planned for westward extension by 2020.
Paris-Gare de Lyon (or Gare de Lyon) is one of the six large mainline railway station termini in Paris, France. It handles about 90,000,000 passengers every year, making it the third busiest station of France and one of the busiest of Europe. It is the northern terminus of the Paris–Marseille railway. It is named after the city of Lyon, a stop for many long-distance trains departing here, most en route to the south of France. The station is located in the XIIe arrondissement, on the north bank of the river Seine, in the east of Paris.
The station is served by high-speed TGV trains to south and eastern France, Switzerland, Italy and Spain. The station also hosts regional trains and the RER and also by the Gare de Lyon metro station.