Paris Rapid Transit: The Four Levels of Nomenclature

A continuation of this post.

The core branding idea of the Paris RER is a really powerful one.  Here’s
how it used to be presented, as a consistent citywide product
(click to enlarge; full-size map here):


Focus on the red line, Line A.  Its a single line across the center of Paris
with branches on both ends.  The common segment in the center has a
high enough frequency that you can use it as though it were a metro
line, while the branches are less frequent but still very good service
for outer suburbs.  The branches are called A1, A2, etc, but the common
segment is just Line A.

This branding scheme is a good example of the principle that simple services should be presented in ways that make their simplicity clear.
Customers should be presented with complexity only if they need the
more complex information, such as to select the correct outer branch for
reaching an outer-suburban destination.  So on the RER, if you need to
go to, say, Euro-Disneyland in Marne-la-Vallée, you need to select the
suburban branch called A4, but if you just want to ride on the metro-like segment within the core of Paris, you just need to remember
Line A.  The system provides one level of nomenclature for
describing the simple common segment, which is all that a huge
percentage of riders will use, and a second more complex layer only for
the people who need that complexity.

Actually, there are FOUR tiers of information here in a clever hierarchy, all designed to ensure
that you don’t have to learn more information than you need to do what
you’re going to do:

  • A Métro route number signifies a simple, frequent line that doesn’t
    require you to learn much more, apart from riding it in the correct
  • An RER route letter such as Line A identifies the common RER segment
    across the core of Paris and invites you to use it exactly as if it
    were any other metro line, without caring about its branches.
  • Odd vs. even numbered branch numbers on the RER indicate different
    directions on the common segment.  On Line A, for example, odd-numbered branches are all in the
    west, even numbered ones in the east, so as you get to know the
    service, the branch number tells you which way the train is going on
    the central segment.  Even if you’re not riding onto
    a specific branch, this can be useful, as redundant ‘confirming’ information, to assure you that you’re riding in the correct direction.  This is important as it’s very easy to lose your sense of north (if you ever had one) in the warrens of underground stations.
  • Finally, the individual branch numbers are needed ONLY if you’re
    headed for a specific suburb beyond the branch point, such as

The principle is that this is a progression from simple to complex.
The point of this hierarchy is not to lead customers all the way
through, but exactly the opposite: to enable them to “get off,” ignore
the remaining layers, as soon as they have the information they need.

But alas!  SNCF has demolished this system on the RER lines that they operate (C, D, and E) and replaced it with something that requires the customer to learn much more complexity.  While the letters are still there, they are receding in the information system.  RER branch numbers (C2, C3 etc) have disappeared entirely on the SNCF-controlled lines.  Instead, users are confronted with a single line number (C) and then the names of various possible endpoints.  Sometimes, as on this sign, the endpoint appears without even a line number — a throwback to how the Métro was presented before line numbers were introduced in the 1970s.


Endpoint-based nomenclature is common in many rail systems, but it carries several nasty problems when used without line numbers or names:

  • Every time you extend a line, you’re renaming it.
  • Endpoint nomenclature in the absence of even a line number (as in the disturbing sign above) can create confusion between different lines that travel to the same endpoint, but by different routes.
  • Endpoints are a lot more information to remember, especially if you’re on a line that could branch to several possible endpoints and you only need to know that you’re going the right direction.  By contrast, the C2, C3 system allowed passengers to quickly recognise the direction of the train (odd vs even) without caring which branch it went to.

This is especially a problem on Line C (yellow on the map above) because one of this line’s southeastern branches, the C8, wraps around to the west to end at Versailles, which is also served by western branches on the same line.  So if passengers must rely on the names of endpoints to figure out which way they’re going on the core Paris segment, ‘Versailles’ is going to be misleading.  (Sydney readers may be reminded of the experience on Cityrail at Lower North Shore stations, where trains in both directions can have the final destination ‘Hornsby.’)  The C8 designation was more useful in helping customers see that this is one of the eastern branches — and thus denotes a train going east through the Paris core — despite its ultimate endpoint in the west.

So here’s what I’d like to posit based on the RER story, and many others.  As always, please argue with me.

  • An effective customer-oriented system of nomenclature focuses on distinctions that will matter to the customer, such as indications of frequency and relative speed vs stop-spacing.
  • An especially good system provides levels of detail couched so that the customer is not forced to learn more detail than she actually needs.  The four levels of nomenclature in the Paris rapid transit system do this especially well, but focus on this is being lost on the SNCF’s RER lines, possibly as a result of an over-emphasis on promoting SNCF as the operator of the service.
  • In an environment without direct customer choice between competing operators, such as urban rapid transit, operator logos seem mainly to serve the needs of institutional ego.  Meanwhile, these logos can distract from, and thus undermine, efforts to present a complete citywide system of routes that work together for the customer.  (There are a few exceptions to this principle in other cities; for example, in the era when New York City had competing subway companies running under parallel Manhattan avenues, these lines were so close together that a customer really could choose between them for the same north-south trip, but that’s clearly the exception rather than the rule in urban transit.)
  • There is nothing wrong with having a brand that unites and integrates all the commuter rail services in the Paris suburbs, as Transilien purports to do.  The only problem with this brand is that it currently belongs to SNCF.  I hope that SNCF is encouraging RATP to use the same brand on its own RER services, so that it can come to represent the entire network serving trips in the Paris region.
  • Finally, getting nomenclature and branding right is hard, especially where there are multiple operators and/or agencies who like to see their logos out there.  Most cities I’ve worked in don’t try to do anything as sophisticated as the original RER nomenclature system, or to extend it across so many services.  Paris currently presents some nomenclature problems, but these are problems only compared to the very high standard the city has set for itself.  The question for other cities is really about how far they want to aspire in the direction of comprehensive legibility, and if so, what they can learn from the Paris experience, both good and bad.

11 Responses to Paris Rapid Transit: The Four Levels of Nomenclature

  1. Yonah Freemark October 7, 2009 at 2:35 am #

    I think you’re exactly right — the observation about the problem with Versailles is spot-on; you can take a train in both directions and end up in the same place. I think that SNCF would be doing its customers well by advocating more use of the numbers-ending of the RER names.
    That said, the problem in Paris itself is that it isn’t always clear which direction you’re going in, and the numbers only complicate that issue if you don’t know the system by heart. One way to solve that would be to have direction signs within Paris that say which end point in Paris you’re heading for. For instance, if you’re on the A at Auber, you would see one sign for A1/A3/A5 to Charles de Gaulle-Etoile and another in the opposite direction for A2/A4 to Nation.
    On the other hand, this might make things even more confusing…

  2. Angus Grieve-Smith October 7, 2009 at 6:30 am #

    This is a fascinating post, especially since I’m planning to talk to my class about levels of detail on Friday. In fact, I learned about the value of different levels of description in my class with Jacques Filliolet at Nanterre.
    I actually don’t remember ever paying attention to the branch numbers – odd/even or beyond; I just knew that the trains that went to Saint-Germain always stopped at Nanterre-Université.
    The RER and Transilien have an additional level of detail for employees, transit geeks and customers who are regular enough to pay attention to things like this. Every train has a four-letter route code. These codes are shown in the posted schedules, in the platform departure boards, and in LEDs on the front of the train itself.
    The first of the four letters always indicates the actual terminus of that run, not the end of the line. The others are usually chosen to be as pronounceable as possible (like YGOR), and each combination is assigned to a particular sequence of stops.
    So for example, the Saint-Germain branch of the A line (PDF) starts the morning with eight ZEBU runs about fifteen minutes apart. These make all stops between Boissy and Saint-Germain. Just before 7AM, as things start to get a bit busy, they alternate between ZARA, which goes from La Varenne-Chennevières to Saint-Germain skipping two stops in Chatou and Le Vésinet, and XUTI, which goes from Boissy to Le Vésinet-Le Pecq skipping Nanterre-Ville. At around 8AM, an YCAR route from Torcy to Rueil is added to the mix. Shortly before 9AM, they go back to the all-stops ZEBU run every ten minutes for the midday period. You can read the rest yourselves.
    Regulars on the Long Island Railroad, for example, always know that the 6:36 to Wantagh skips Lynbrook, but the 6:46 to Babylon stops there. The four-letter designation allows regulars in Paris to know that the 6:45 and 6:55 ZINC trains out of Etoile won’t stop at Chatou, so they need to be on the 6:50 XOUD run.

  3. Louis Haywood October 7, 2009 at 7:14 am #

    Kudos for mentioning the 4-letter signs, I always enjoyed ZEUS on the RER A, but I can’t remember my old RER C train.
    However, Jarret’s complaint about the SNCF services is somewhat diminished because of the 4-letter signs, but also, and more importantly, because each RER platform has multiple flip-boards or LED signs (in the case of the RER E) which list EACH and EVERY stop on that train. So by reading the sign, one can get all the information one needs.
    This information is really more critical than the simple branch numbers. For instance, if I am at Chatelet-Les Halles taking the RER B to Antony to catch the OrlyVAL to Orly Airport, then “B” or “B4” isn’t enough, and neither is “St-Remy”. I need to see the “ANTONY” box lit on the platform screen to know I can take this train to Antony and catch my flight.
    I can say from experience that no tourist has ever been able to figure out how to take the RER C from Champs de Mars Tour Eiffel (Eiffel Tower) to Versailles, without asking five different people. There are two Versailles (Chantiers and Rive Gauche). SNCF tries by putting an image of the Palace on the switchboard next to the name, but taking branching trains into the distant suburbs is something any tourist will want to be absolutely sure of, especially in Paris.

  4. grvsmth October 7, 2009 at 1:32 pm #

    Good points, Louis! There are actually three train stations in Versailles including Versailles Rive Droite; it’s a big town. I agree that tourists are always confused. Probably the best thing to do would be to rename Versailles-RG to “Château de Versailles.”

  5. Scott Workman October 7, 2009 at 1:46 pm #

    Thanks for putting this in such succinct terms as I am finding all of your posts to be. When coming to a new place, I think this is incredibly important to have a hierarchical (simple to complex) set of directions. In my own experience after a week or so getting used to a city, San Francisco & St. Louis being the last couple of cities I was in with good and decent transit respectively, riders inevitably just want to make sure they are heading in the right direction. They have a mental map seared in their brain of the things that they need for their daily trip and just need to be on the right (or left) side of the platform.
    Going back to your recent post about first impressions of a city and its transit amenities, this is also a very important impression to make for a first time rider who is considering becoming a transit commuter vs. a motorist. A potential customer could be equally turned off by a system with poor signage as he/she would be by a woefully inadequate ticketing system and poor customer service.

  6. anon October 7, 2009 at 3:27 pm #

    I would have a slight quibble with the 1st of the four tiers you mention. Coming from New York’s highly-oversimplified ‘uptown/downtown’ scheme, I find it can be challenging to remember two/three terminal stations for 14 different lines (some with branches) for rapid cognition when choosing a direction to take on the métro. The one mitigating factor being that there are often signs when you get to the ‘point of no return’ listing all of the stations going to that terminus (similar to RER).

  7. J October 16, 2009 at 10:24 pm #

    The C branch has always been a clusterfuck from an outsiders perspective. In the north everything is fine and then WTF is happening.

  8. agus February 14, 2010 at 10:55 am #

    you have a great site, an valuable information. thanks

  9. Andrew July 3, 2010 at 9:52 pm #

    Yes, I certainly recall getting lost on the RER to Versailles on our trip to Paris several years ago (this being in the pre-Google Map days, so we didn’t know our way around). A major problem is that it is not immediately obvious to tourists that Versailles-Chantiers and Versailles-Rive Gauche stations are only a 10 minute walk apart, so it is probably faster to take the first train to Chantiers rather than waiting for a train for Rive Gauche at least at certain times of day. Another problem is that Versailles-Chantiers is also served by Transilien trains to Paris Montparnasse; we accidentally got on one by mistake when going back to our hotel, which fortunately was reasonably convenient for us.

  10. John G. September 9, 2010 at 12:14 pm #

    Agreed, C Branch definitely messed up.