Dear guys. I hope you are well. I am travelling from Gare du Nord to Montparnasse on the metro. I only have one hour. My wife and three month son are with me so we need to make up every second as possible. When we get on line four for montparnasse bienvenue. Which carriage is best to get on. So we are close as possible for the walk to the main station montpaarnasse? Thanks
Metro 4 platform exits are at the middle of platforms at Montparnasse Bienvenue.
Unfortunately it's a fair walk from the Metro 4 exit inside Montparnasse Bienvenue towards Gare Montparnasse. It's about 7 minutes walk to Gare Montparnasse, so the 20 seconds or so difference between the ends of the train vs the middle, may not be significant.
It is less of a walk (about 4 minutes) from Metro 6 towards Gare Montparnasse, where you would ride the RER B to Denfert-Rochereau, then switch to Metro 6 (direction Charles de Gaulle-Etoile / Arc de Triomphe) until Montparnasse Bienvenue. But, this requires a transfer which may make the overall travel time roughly the same or worse depending on your luck with timing between trains.
Repeated over dozens of times, the RER B to Metro 6 route should be on average 2 minutes shorter / quicker than the straight Metro 4 + longer walk to Montparnasse.