When travelling on German DB trains with a seat reservation, you usually get a car number and a seat number. Seat numbers are integers unique within each car.

Typically, these seat numbers are distributed in a somewhat sequential manner from one end of the car to the other. However, I am saying somewhat because it has happened more than once to me that I missed a given seat at first. Within each row or pair of rows, seat numbers seem to be distributed according to a pattern that I do not quite understand yet.

To illustrate this, here is a partial screenshot of the seating scheme from an IC car that can be accessed while booking a train ticket on bahn.de:

Screenshot of bahn.de - grafische Sitzplatzauswahl

When looking at seat numbers in such a schematic view, it looks like seats are always numbered in groups of eight (i.e. across two adjacent rows), adhering to the following schema:

5 6
7 4

3 8
1 2

Now, when standing in the aisle in the middle of seats, that schema does not become quite as apparent (thus leading to some confusion when searching for one's seat, especially when subject to limited mobility due to luggage, children, or other passengers in the aisle). Is there anything to avoid about numbers ending in 9 or 0 so they do not appear based upon this schema? And anyway, I wonder whether there is any system behind distributing the numbers within such a block of eight seats.

What is the reason or benefit behind this way of numbering seats?

EDIT: While there seem to be a couple of numbering schemes, my impression is that at least "normal" IC and ICE trains feature the numbering as described above. Thus, I would like to exclude any additional numbering schemes from yet other train types from the focus of this question, although other special cases that I did not cover here and that do appear on IC or ICE trains (e.g. unaligned tables, maybe) are still within scope of the question.

  • In general (but also here, there seem to be exceptions), only wagons used in IC or EC trains have seats ending with 7 and 8 on opposite sides of the aisle. In ICE trains seats with numbers ending with 7 and 8 are usually on the same side of the aisle. If you are interested, you can find a relatively up to date document with schematics of all different kinds of passenger wagons used by DB here: kursbuch.bahn.de/hafas-res/img/kbview/ContentPDFs/… Sep 4 '17 at 22:41

The numbering scheme is based on historical international standards. Those were originally developed for compartment coaches, which is why always two rows are considered together (one compartment had two rows of opposing seats). The numbers aren’t consecutive because the first digit is the “compartment number”, independent of the place number in each compartment (last digit).

When the system was conceived, compartments usually had six seats. It was defined that seats 5 and 6 are at the window; in order to keep that consistent for eight-seat “compartments”, the additional seats 7 and 8 had to be inserted in the middle.

  • 2
    "the additional seats 7 and 8 had to be inserted in the middle" - but then, why diagonally rather than as an additional 7 8 column? Also, do you happen to have any source/reference for this explanation? Sep 4 '17 at 21:55
  • 2
    This answer seem to explain only half of the problem raised. Some DB open coach cars don't add the seats 7 and 8 on different sides of the aisle, and use the ordering 5, 6, 7, 8 / 3, 4, 1, 2 instead of 5, 6, 7, 4 / 3, 8, 1, 2 as used in the example in question. If there are groups of four facing seats (mostly around a table), these also have a common first digit in the seat number. If the tables are not aligned on each side of the aisle, this can lead to rows of seats with a different first digit on each side of the aisle. Sep 4 '17 at 22:00
  • Some trains also use a completely different numbering scheme. The open coach cars in the CNL trains used an odd last digit for window seats and an even last digit for aisle seats, so seats with a number ending with 6 were not window seats. Sep 4 '17 at 22:12
  • 4
    And to mention yet another odd deviation: In the ICE3 train sets, the 2nd class open coach section of wagon 26 uses a different numbering scheme than wagons 21-24. With the Germans having a fable for order, I am not sure that this is just a coincidence or if not some kind of meaning is encoded into the numbering scheme. Sep 4 '17 at 22:18
  • 2
    I've posted this question to DB on Twitter. Their short reply seems to confirm this answer: It relates to the numbering on old compartments.
    – simbabque
    Sep 7 '17 at 9:09

This clever seat number system, dating from the pre-computer era, was an easy way to maintain an even distribution of passengers over the train, when the train was not yet fully booked. Passengers would get annoyed if the distribution was carelessly uneven.

Initially the seats x1, x2, x5, x6 were assigned by the booking system, and all passengers had some free space at their side. When all x1-2-5-6 seats were full, the x3 seats were assigned. Next the x4 seats, then x7, and finally x8. The system worked fine for trains containing combinations of 8 and 6 seat groups, 8 and 6 seat compartments, and 6 or 4 sleeper compartments.

8 seat group:
window . 91 93 . aisle . 97 95 . window
window . 92 98 . aisle . 94 96 . window

6 seat group:
window . 91 . aisle . 93 95 . window
window . 92 . aisle . 94 96 . window

8 seat compartment:
window . 91 93 97 95 . aisle
window . 92 98 94 96 . aisle

6 seat compartment:
window . 91 93 95 . aisle
window . 92 94 96 . aisle

4/6 berth sleeper:
bottom . 91 (93) 95 . top
bottom . 92 (94) 96 . top

This numbering system was used for long-distance trains and international trains in Europe, and it was part of the Regolamento Internazionale delle Carrozze (RIC), an international railway agreement that facilitated the cross border use of cars.

  • This answer is very interesting, but unfortunately, I also feel it does not really answer the question. The issue I'm seeing is that everything described about the even distribution of passengers would be just as easily possible with any other numbering scheme (including one where seat numbers strictly increase as you move from one end to the car to the other), provided that the window seats end up with the same last digits irrespective of seats per row. Dec 1 '18 at 22:10
  • I think my main point is that the strange numbering had the advantage of simplicity when reservations were made, in the pre-computer era. Another advantage was that groups of two of three passengers, if they booked early when there was ample choice, could easily verify that they were facing each other by a simple rule, independent of the number of seats in the compartment. Two passengers would get x1-x2 or x5-x6, three passengers x1-x3 or x4-x7.
    – jkien
    Dec 2 '18 at 10:54
  • Oops, the last "word" of my above comment should be "x4-x6" instead of "x4-x7".
    – jkien
    Dec 2 '18 at 11:05
  • That's exactly my point (and maybe I'm missing something there): I fail to see any advantantage for the described goals over a sequential numbering scheme. That is, if seat numbers were 91 - 92 - aisle - 93 - 94 / 95 - 96 - aisle - 97 - 98 (skipping e.g. seats 93 and 97 in 6 seat groups), it would be just as easy to evenly distribute passengers by first booking seats 91, 94, 95, and 98. Dec 2 '18 at 15:42
  • Your alternative might have worked equally well in practice, maybe at the time agreeing on a single system was more important than finding the "best" system. An advantage of the chosen system seems to be that a group of two passengers gets consecutive numbers (x1-x2 or x5-x6); and that seat reservations x5-x6 surely are window seats, without specifying if is a 6 or 8 seat group. Your alternative doesn't have this advantage. Would it really have been an important advantage? We don't know.
    – jkien
    Dec 3 '18 at 7:13

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