French Trains? Connection times?

If I'm interpreting this diagram correctly, the station in Rennes has 10 tracks accessed via 5 platforms. Transfer times are sufficient when trains run on time. I have never missed a transfer, and I'm a senior citizen who always has a larger-than-carry-on bag to deal with.

Finding the new platform is not usually a challenge (and the diagram shows the layout at Rennes to be simple). It's a matter of knowing your new platform number and physically getting to it, which normally requires going down a level, walking a very short distance and then going back up. (Rarely, one walks up and then down.) Sometimes there are escalators.

If you put the SNCF app on your smartphone, I believe it will tell you which platform your second train departs from. Otherwise, there will be signage showing platforms and destinations. If you must walk through an underground tunnel, there will normally be such a sign for the departing trains (one or two) at the base of the stairs going up to each platform.

I barely speak any French at all but have managed to ask SNCF employees where to head by giving the name of my destination in a questioning tone; it helps if you understand numbers (of tracks) in French, because not every random SNCF employee speaks English. Ticket checkers on your first train may be able to help, but sometimes platforms are not assigned very far in advance, to the ticket checker may not have the information.

It isn't unheard of for trains to be a few minutes late. Sometimes one trains waits a few minutes for the late train, but there certainly are no guarantees. It's probably the case that a regional (slow) train is more likely to wait for a TGV (express) train than vice versa.

What is your origin point? What is your destination?

I can't answer to SNCF on-time record. But the station layout is pretty standard with 4 central platforms 10 tracks. If your connecting track is not on the same platform, you take the escalator up to the cross-over bridge, walk to the next platform with your track, then down the escalator to your new track. Should only take 5 minutes at most. Here is a diagram of the station.
https://www.garesetconnexions.sncf/fr/gare/frrns/rennes/plan-de-la-gare

Edit. Looks like acraven posted before me. Only to say that it is a cross-over bridge at this station, not a tunnel, to get between platforms.

Thank you all. Great app for the diagram. Just what I had been searching for!

We are traveling from Saint Malo to Paris. We can either travel through Rennes or go straight. About the same time but we take into account which way sees more of the countryside/new sights for us.

In that case you are starting out on a regional train and switching to an express (TGV) at Rennes. With luck you'll make the connection. If not, SNCF will allow you to take a later train from Rennes. I'm not sure what the proper procedure would be, because I haven't missed a train like that. You could go to the information counter inside the station and ask. Perhaps an SNCF official has to make some sort of notation on your ticket??

The direct train from Saint Malo to Paris follows the exact same route as the regional train + TGV combination via Rennes. Therefore, you will not see anything more if you choose the latter! Book the direct train.

I just took nine trains in France in the last three weeks. Some were connections. I never really had a problem except having to lug my bags up and down stairs when there was no elevator or escalator. Or they were not working.

SNCF is not the best run operation in the world but it gets you there. So I also suggest you take the direct train. Same route either way.

Very good to know!

Thank you all! We will try the connection as it will get us to Paris two hours earlier. Much appreciated!

and remember to compostez

If you have your tickets on your devices or printed at home you do not need to compostez (which is to validate it in the yellow stamping box).