Very good question
Nothing really, the only thing some people found confusing was the K, L, M gates within 2E. No big deal, but they could have addressed this by just calling those gates E1 to Esomething. Instead of doing it simple, they have come to this choc de simplification that will be quite costly when you think about it. So ADP...

There are two sides to that answer:

1) What was wrong: the numbering of terminals wasn�t intuitive at all, did not reflect latest real estate changes (=merging 2B/D and 2A/C), and was partly totally confusing (2E-K,L and M). Therefore, yes, there was something that needed fixing.
2) Is the new concept better: opinions differ, but personally I find the re-numbering of terminals useful and more intuitive. Where they then throw away any gain in intuitiveness is by giving letters to boarding areas, which not only is not necessary but also is done in a totally random and non-sensical way. It�s a situation where the result obtained by addressing a real flaw is worse than the original situation. Some sort of �degradenhancement� (German speakers recognise �Verschlimmbesserung�)

End result: the new labelling may not be much better than the existing one.

It was already explained why the letter prefixes are "necessary", or at least substantially improve navigation around the airport. As for the letters chosen being non-sensical, in what way? Apart from maybe not looking most logical on a map (that no one uses), how will the choice of these specific letters negatively impact passengers?

The new flow of passengers will be very simple: Check-in (if applicable) at the terminal noted at your ticket, then follow signs for the gate area mentioned on your boarding pass. I can't see how this could be improved. Dropping letters from the gate numbers would only create more confusion, because suddenly you'd have no easy way to tell passengers to go e.g. to F gates before knowing which particular F gate will be asigned to their flight. And no, you can't use terminal number because gates don't correspond to "check-in terminals" 100%, and again, trying to tell passenger that they should "check-in in terminal 5 and head to gates at terminal 4" is no better than the proposed setup, not to mention that it's not supported by data structure of flight data in GDS and other systems (there's just one terminal number).

The same setup as proposed here exists at VIE, which is my home base. You arrive to the airport, head to the terminal noted at your ticket for check-in, then follow the signs to the gate area (C, D, F, G) on your boarding pass - any terminal / gate area combo is allowed (e.g. T3 has departures from C, F and G gates, possibly D too). It's extremely intuitive and I don't encounter dozens of lost passengers confused by why there's no E gates.

The current numbering is too simple. It needed a "choc de simplification".

Also, AF unions were wondering why 2E halls were labelled KLM.

There is 0 reason why gate numbers should be tied to departure terminal. Indeed there is a very good reason why they shouldn't - the layout of airside areas does not correspond to the layout of landside areas.

The reason that 2E-KLM confuses people because they have to go from E to K/L/M not because they have to go from 2 to K/L/M.

There is no way they are that pettty.

� Explained �, surely, but that doesn�t mean the argument is compelling. I understand it when several � terminals � lead to several boarding areas and things can overlap. You mention VIE as a perfect example, and there are many others.

But in airports where there are distinct terminal buildings (CDG, JFK, LHR�), there is no need. Which means that in the case of CDG, with the exception of the new Terminal 5 which has distinction boarding concourses (some need to be reached by train, others not), there is no such need. You check in Terminal 1, you go to gate number x or y, which are necessarily in that terminal. You check in Terminal 2, you go to gate number x or y. And so on.

Alternatively, if one really is convinced that there have be no two gates with the same number in the entire airport, you could just prefix every gate number with the first number of the terminal. All gates in T1 start with 1xx, in T2 they are gates 2xx, and so on.

I agree with you, many people don�t think about certain things, they just follow signs. So they can just as well follow signs to � Gate 1xx � which would logically be in T1 or follow signs to � Gate 6xx � which would logically be in T6. There is no need to use those letters, which just add another layer of structure (fair enough, if you think that is needed), which has nothing to do with their location (that is just adding unnecessary complexity).

But in any case, there is no need for us to agree, ADP will do it anyway. Which will help some people, confuse some others, and I just take as another example how in France we love to over-conceptualise things which could be so simple and straightforward 🤣

I used to think the same until I was exposed to the German corporate culture. Since then I give them the over-engineering crown every single time

Anyway, at this point I'd take basically any solution that tries to clean up the mess that are lettered parts of Terminal 2.

They aren't that distinct though. Which is why they're currently all terminal 2.

But you don't. You check in Terminal 5, you go to one of 3 different concourses. You check in Terminal 4, you go to one of 2 different concourses, one of which is shared with Terminal 5 and better connected to Terminal 4. You check in Terminal 4, you go to one of 2 different concourses. You check in Terminal 1, you go to... something that used to be 7 different concourses thought up back in the 60s, but can at very least be separated into Schengen and non-Schengen gates.

Except that CDG doesn't have distinct terminal buillding in the same sense JFK or LHR have. The main difference is that you may check-in in one "terminal" and depart from another - which is exactly the same situation as in VIE, hence the same solution.

But how is your solution any better? How is 1xx better than e.g. Dxx? Because I gave you an argument why ADP's solution is better - you can easily point people towards a group of gates even if you don't know the specific gate the flight is going to depart from. It's much easier to print "D" on the boarding pass instead of "101-137" (the same applies to signage, if you have a path towards E, V and Z gates, it's easier to put those three large letter on a sign then "101-137, 301-348, 701-732"). I miss any valid counterargument why the numeric solution would be better in any way at all. The only argument I read was that gate numbers would match the terminal, but that's actually a bad thing, since you may depart from terminal 1 but your gate may actually be in terminal 7.

(The numbers and letters I used as an example to demonstrate the principle, I'm aware the exact numbers and letters will be different at CDG.)

See above, this actually creates more confusion. I also suspect it's incompatible with systems used airlines for boarding passes etc. (sure, AF could adjust their IT and their BP format to allow "101-137" to be printed but you can't expect all airlines flying to CDG to do that, not to mention that imho it would be more confusing anyway).

So my question remains: Why is the logical flow of "depart from terminal 1, gates V" worse than "depart from terminal 1, gates 301-348"?