Paris to Normandy and back

It's going to be cheaper and easier to just get the car and stay with it the whole way. You'd have to go into Paris proper to catch the northbound train, anyway. Then you'd wind up paying for both a train and a car on the same day. The turn-in day would have the same logic. Get the car at the airport. Dropping it at Gare du Nord is fairly easy, as is dropping it at G. Saint Lazare. It's four hours of road time from Roissy to MSN. Assuming an early morning flight arrival, you've got plenty of time to stop at Rouen - - there's no need to get to MSN until close to dark (unless you want to get in the abbey, then you'd need to get there by around four). A couple of hours is good for Rouen - - three can include lunch. Edit: reread the question and it seems you're leaving from the city. Don't go all the way to the aiport - - it's the wrong direction, anyway. Pick it up at either of the stations above (both have quick and easy access to the freeway) and turn it back in at the same place. You've still got time to swing through Rouen.

Actually we are arriving in Paris a few days earlier and we are staying close to CDG. We had planned to originally get the car on the morning of our road trip, drive to Mont Saint Michel, take in the sights, then by the end of the day, drive to Bayeux and check in early evening. We then planned to leave the Normandy area and drive back to CDG to off the car and check into a hotel close to CDG. But now we are thinking to get to Bayeux first, check in, off our luggage, and then drive to Mont Saint Michel so we are not lugging our luggage in the car, prone to possible break in, a.k.a. smash and grab. Check in time at our hotel in Bayeux is 2pm so that might not work in fitting MSM into that day. I have driven in some rough traffic here in the US (Washington DC metro and NYC metro traffic) but after reading some of the reviews on Paris metro traffic, it sounds like it is worse. Hence why we are thinking maybe the train to Caen from Paris then renting a car from Caen to and from Bayeux and MSM might be better?

We have always taken a train from Paris to Caen where we have a reserved rental car right across the street from the Caen railroad station. Bayeux is about 20 miles and perfect for the first nights stay. You can take an early train, get your car, and have plenty of time to view the tapestry or even take a 30 minute drive to the D Day beaches. MSM is about 90 minutes or a bit more from Bayeux. We arose early and got on the road to arrive before the hordes from the tour buses. About 2 hours was plenty, then we drove around the bay to Cancale for a superb seafood lunch with MSM visible across the bay. We drifted back across the back roads to Bayeux, stopping where we saw local goods, cheeses, Calvados, or just interesting small towns to shop in. We got an early train back to Paris, dropped off our car at Caen, and had a stress free time. We do not like to deal with Paris traffic nor long traffic jams returning to Paris like on a Sunday afternoon. Get a GPS in the US, learn to use it, program into favorites the addresses of you hotel, local museums you want to visit, and the entryway to the rental lot. We also had a Michelin map of Normandy, bought on the internet, since the GPS might want to take you down some very rural back roads instead of staying on the motorway. You might consider staying 2 nights in Bayeux since you will find that there is much to enjoy there.

Okay, I'm starting over. First, no train. It's going to take you an hour to get into Paris and then across town, minimally. The train from Paris to Caen takes a couple of hours, then you've got to pick up a car and drive to MSN - - that's two more hours at best. You've used up five hours, probably six. You can drive from CDG to MSN in four hours. No matter which course you take, you're going to have to go to the airport to either pick up the car or catch the rer into Paris, so that's a wash. I'd have no concern about stuff in the car at MSN. I've done it a couple of times, at least. That parking lot is so busy that I don't think anybody would have the guts to bust a window. Plus, there's usually fuzz around. No matter how you do it, you can't beat the crowds if you go to MSN on the first day. Figure you'll need three hours there if you want to include the abbey, less than two if you don't. If you pull out of CDG at eight, you should hit Bayeux around three or so, giving you time to catch the military museum or the tapestry museum but not both. You won't even be driving in Paris within the peripherique, so whatever you think or suspect won't even be an issue. And, Paris is much easier than either DC or NYC by a long shot. If you're really worried about your stuff in the car, you can swing by you hotel early and drop it off - - a very common practice. This, however, will add at least an hour to a day that's already pretty long. Don't even think about Cancales, it's at least an hour over there and an hour back to/from MSN and you'd be looking at the speck of MSN from fifteen or twenty miles - - it's barely visible if there's any haze.