We do not need to worry about transportation when we arrive in Paris, as our landlord provides limo pick-up service for her guests. However, we want to use public transit for our departure. This will involve taking the M1 line from Franklin D Roosevelt station to Chatelet-Les Halles, and then transferring to the RER B line. Our flight to Canada leaves at 1:30 PM, so we won't be taking the transit in rush hour. When I use the RATP inter-active route planner, it shows the route as M1 - M4 - RER B, with a very short duration on the M4 between Chatelet and Les Halles. This is confusing to me, would we not just walk from the M1 to the RER B in the underground station which connects Chatelet and Les Halles stations? Thanks in advance for your suggestions.