45 minutes between trains...too close?

I would book a car service to pick you up at Gare St. Lazare. Not the cheapest solution, but then you would have one less thing to worry about. 3.5 hours is just too long.

If you know your way between the railroad stations and there is no delay, 45 minutes should be enough. To be safe I would probably book the next train to Avignon.

You can probably make it, but I am terribly conservative on these transfers and usually plan a lunch stopover in Paris instead of rushing. We typically go to the departure station, check our bags, then go find a nice lunch and have a walk.

I tend to be very conservative on such things, but since the 14 metro links these two stations, I'd probably risk it. Train platforms are announced about 20 minutes before departure. I would not chance it with car or taxi, only with direct metro where the chance of delays are very small. I have been stuck in cross town traffic in a cab and would never do car transport with a tight transfer.

The cars of métro 14 travel very fast. As long as M14 is operating normally, you should take it and not worry. Gare de Lyon has two different sections from where trains depart. Know where they are and be ready to go to either location once you arrive at the station. Departure platforms are posted about 15 minutes before scheduled departure.

Do you have a lot of luggage? If not, take the metro. The 14 metro line takes about 10 minutes from Gare St. Lazare to Gare de Lyon and leaves every 3 minutes. Add time to walk to the metro and up to Gare de Lyon from the metro and it still beats the roughly 32 minutes surface traffic time (assuming no unusual delays). The fare is 1,90.

People make the mistake of believing a taxi is the fastest option. It's better to say a taxi is the easiest option when you have a lot of luggage.

Thanks everyone. It seemed doable to me but I wanted to check with all of you. We have learned to travel light so we will not have a lot of luggage. We will take the train between stations and hope there are no delays!!

It will be handy if you have your tickets for the Métro ahead of time. Will you have any left over so you don't have to buy them?

I would highly advise the metro line 14 over a car service or taxi. Covering that distance in a vehicle on the surface will take a lot longer than zipping across town on the 14.

Nigel makes a good point about the good idea of having metro tickets already in hand if possible to make the trip even faster.