The trains on this sector depart from Gare Saint-Lazare in central Paris and serve the north and north-west of Île-de-France region with Transilien lines "J" and "L".

The trains on Line J travel between Gare Saint-Lazare in Paris and the north-west of Île-de-France region, with termini in Ermont–Eaubonne, Gisors and Vernon.

The four-letter code begins with a letter that designates the terminus of the station.

Typically, mission codes or the name of services of line J have the following composition of destination, vowel, consonant, vowel (CARA, GENE, MOLE, PALE, TOCA, etc.)

The trains on Line L travel between Gare Saint-Lazare in Paris and the west of Île-de-France region, with termini in Cergy, Versailles and L'Étang-la-Ville.