TGV Connections

Did you check the SNCF website? Click on the British flag in the far left lower corner for the English version.

The TGV network has Paris as a hub (with one exception) - only way that they can have sufficient number of passengers - like airlines: there is a map somewhere deep in the obvious SNCF site above - an (slightly outdated I think) here and googling tgv map will give you others.

I find the SNCF website unnecessarily confusing for a simple trip. My personal
preference is for the bahn.hafas website, link:

bahn.hafas train schedules(in English)

All you need to do is type in your departure site (Tours) and arrival site (Avignon TGV),
add your date of travel and approximate age (for computation of fare discounts).

Press search, then details, and it shows you everything about your trip - if a
metro ride in Paris is needed, it gives you the stops and transfers needed, along
with the elapsed time on the metro or RER.

Doing this, my personal preference would be:
dep Tours at 08:13 on TGV 14050,
arrive Paris Austerlitz 10:50,
walk (or if lots of baggage, take 800 meter cab ride) to Paris Lyon station,
depart Paris Lyon 11:20 on TGV 6111
arrive Avignon TGV at 13:58.

Many other choices will be presented to you in their ENTIRETY, including the parts
now troubling you. Other choices may be better for you personally than the one
I just wrote up.

Try it. You might like it.

Elliott Moore

Yes a common difficulty when travelling through Paris by train is that you need to change the train station. And I also agree the SNCF site is very confusing in general.
In your case, the subway should be the most efficient here because its a direct connection. But if you have a lot of luggage consider a taxi.

There is a cross country (non-TGV) line from Tours to Lyon where you can connect at the same station to a TGV to Avignon.

It will probably be slower and less frequent than via Paris though

Indeed it is possible to NOT go through Paris, if that is a problem. Example:
on the bahn.hafas site, give "Bourges" as an intermediate stop, but the
same initial (Tours) and final (Avignon TGV) stations. That forces the direct route.
An example of doing this is:

dep Tours 06:17 arr. Bourges 07:58,
dep Bourges 08:05 on RE16831,
arr. Lyon Part Dieu 11:35, depart on TGV 5149 at 11:45,
arr. Avignon TGV 12:49.
Total time elapsed is 6 1/2 hours, and you avoid Paris altogether (Note: this
route does not operate on Sunday).

You could aslo avoid the TGV altogether if you wished. Give as intermediate
stops Bourges AND Nevers. That results in 5 train changes and an elapsed
time of 9 1/2 hours. You also wind up in Avignon Central, not Avignon TGV -
which may be an advantage depending on your travel details after exiting
the train system.

Elliott Moore

It may help to know that Tours is not on the main rail lines. Instead, a station is the suburbs of Tours (about 3km from Tours) is on the main rail lines, and this staion is called St-Pierre-des-Corps. You can reach that station either by a 5-minute train ride from the station in Tours, or by taxi, and probably also by bus. (In other words, service to Tours is actually via a "spur" line from a tiny station in the suburbs which sits on the main rail lines!).
If you use that station name as your starting point, and Lyon as your destination, it'll be simpler to find trains.
The TGV line connects Lyon with Nantes, and the TGV runs through St-Pierre-des-corps, and goes via Massy, which is a station in the southern suburbs of Paris. There'd be no need to make a transfer between stations in central Paris unless you wanted to. In that event, there's a bus that connects Montparnasse with Gare de Lyon, and the transfer is MUCH easier than using the metro (I can't remember now the number of the bus, but I do remember that it was easy to find).
I did have a quick look at connections from St-Pierre-des-Corps to Lyon, and found two TGV connections, one shortly after 08:00, and the other in the 14:00 window--- and that later one actually continues to Marseille, and stops at Avignon, so you wouldn't even need to transfer trains at Lyon.

Basie has made excellent suggestions. (1) Start at St-Pierre-des-Corps,
(2) look for the simplest connections.

The VERY SIMPLEST procedure for you is no connection at all, no change in trains.
That one possibility is to depart St-Pierre-des-Corps at 14:38, TGV 5322, and sit on that train
until it arrives at Avignon TGV at 18:52. That train does pass through Lyon Part Dieu
but no action is required on your part at that station.

If you investigate Basie's Massy suggestion, be wary of a required station change inside
Massy to continue, required on some possible routes. There are also other simple single
train changes, one at Lyon Part Dieu requiring nearly an hour's wait for the next train;
or another single change at Marne la Valle-Chessy involving only a nine minute wait
in the same station.

Stick with the one-train solution - that will work!

Elliott Moore

St. Pierre des Corps is not a "tiny" station, and has frequent TGV service towards Paris. In any case there are free navette trains that go regularly from the Tours station to St. Pierre every few minutes. No need to take a taxi or bus. As stated above, you can easily connect at either Masssy or Marne la Vallee (or even CDG), with few problems.