I'm in the process of buying 2 one way TGV tickets from Avignon to Paris CDG on August 1 at 17:51. The SNCF website lists two TGV train #'s both leaving at 17:51 so, I know it's the same train. One is TGV 5017 and the other is TGV 9882. The prices are identical. It almost sounds like an airline code share. Can some explain this to me?

Thank you!

The second train could be an iDTGV train but more likely is the possibility that these two trains have different originations. One could be originating in Montpellier and a second Perpignan, the two being joined together, either in Avignon or maybe Nimes, for the trip to CDG.

Are they direct trains or is there a change of trains in Lyon Part Dieu - seems like that is the case with such two very different train numbers - on www.bahn.de/en - the German Railways site I always use for schedules of every European train it lists for Aug 1, 2015 at train leaving CDG at 17:58 - # 9836 that changes trains to TGV #5347 at Lyon Part-Dieu.

and even on direct trains some have two TGV numbers - running as such a TGV # up to Lyon-Part Dieu and then a different TGV # for the same continuing train to Avignon TGV.

So interesting. Yes, PalenQ---the second scenario you outlined appears to be correct in this case.

I looked them up and TGV 5017 ends in Lille and TGV 9882 ends in Brussels. Neither require a change of train for me and of course they both make the same stops as far as CDG---which is all that really matters to me. I'd just never seen that before.

Two TGV units run Marseille-CDG-Lille, with two different train numbers 5017 & 9882 but only one (TGV 9882) runs beyond Lille to Brussels.

This is very common with one 'normal' TGV and one 'iDTGV'. If they are both the same price, you can book either one. Generally, the iDTGV trains are supposed to be cheaper.