The lines serve many stations in the region and depart or terminate at the major Paris stations, or at La Défense for Line U. Operated by the SNCF, they even venture outside of the region for a few stops on Lines J, H and R. They were given their current names in the first half of the 2000s but existed for decades before. These trains are essential to the mobility of Ile-de-France residents and this network is very active: every day, there are as many trains running in the Ile-de-France region as all regional (TER) trains throughout France!
