The métro (Mº) runs from 5.30am to 12.30am, the RER from 5am to midnight. Stations are far more frequent than on most underground systems, though many entrances are a long way from the platforms and most interchanges involve long walks and lots of stairs. A choice of three free maps is available at most stations: the Grand Plan de Paris for the whole RATP system, which also usefully overlays the métro system onto a map of Paris's streets; the more at-a-glance Petit Plan de Paris ; or the pocket-sized Paris Plan de Poche . In addition, every station has a big map posted. 

The métro lines are colour-coded and numbered 1 to 14; the RER lines are designated by the letters A, B, C or D. Within the system, you find your way around by following signs bearing the name of the station at the end of the line in the direction in which you are travelling: Direction Porte Dauphine , Direction Gallieni and so on. The numerous interchanges, or correspondances (look for the orange signs), make it possible to travel anywhere in the city in a more or less straight line. 

For RER journeys beyond the city, make sure that the station you want is illuminated on the platform display board