Metro maps are wonderful examples of UX in practice away from the digital sphere. Combine this with the obvious fact that trains are cool and I spend a lot of time thinking about them.

A question has came to my mind today however, and I wonder if there has been any investigation into an answer;

What is the best practice for naming metro lines?

I notice several different methods of doing this in varying systems of the world:

  1. Colour coded. This seems particularly common with metros that only have a handful of lines, for instance that of Tyne & Wear in the UK with its simple green and yellow naming.
  2. Numbered. Line 1, line 2, etc... Seoul uses this. Pretty straight forward.
  3. Lettered. New York uses this. I don't get it.
  4. Geography based naming. You get this in London with for example the Bakerloo Line, named for the two places it connects. This type of naming is also common with lines in Japan, taking a character from significant places on each side to create a new word.
  5. Other naming. Also used often in London. Some lines just have names. Like the Victoria or the Metropolitan. No geography in their name.

From a pure user experience angle, which is the most user friendly? What are the advantages and disadvantages of each?

  • Even purely numeric codes can be more complex than chronological single-digit numbers, e.g. odd vs. even for W-E vs. N-S lines, same digit twice for circular lines, same leading or trailing digit for lines passing the central station or another important hub, fewer digits for the most important and frequent lines or even shared numbers with tram, ferry and bus lines.
    – Crissov
    May 23, 2017 at 17:25
  • which system is this? May 24, 2017 at 12:03
  • Not a single one, but features from different ones I've encountered.
    – Crissov
    May 24, 2017 at 14:02

2 Answers 2


We can try to analyze this from an information load perspective.

  1. The number system probably has the least information. You can more or less deduce which line was built after which - which might be helpful if you're familiar with the history of the city, but otherwise not so much. So it relies on memory alone.
  2. The letter system is pretty much like the number system, but it provides for clearer distinction (above, say, 10, people are more likely to confuse two numbers than two letters - e.g. to say "I don't remember whether it's #16 or #18" than "I don't remember whether it's P or R").
  3. Color coded - helpful for a small number of lines, adds another dimension to the first two systems, helps with both physical navigation and with the metro map. Becomes difficult to manage much faster than the first two.
  4. "Other naming" - excellent distinction, endless possibilities, has all of the upsides of the first two. Since it's usually combined with color coding (e.g. the London Victoria line is light blue), doesn't lose on that front either, except the color is not part of the actual name.
  5. Geographical naming - all of the above, plus gives some very valuable context about the general direction of the line. Even as a tourist you are usually able to quickly grasp the general directions, so it becomes helpful very fast.

That being said, you have to consider the general context - the naming conventions of earlier modes of transportation might support the usability of the metro naming, or they might interfere with it. Also other naming - you often have fare zones, either numbered or alphabetically named. This might not work well with the numbered/alphabetical system of line naming, especially for tourists.

  • "Since it's usually combined with color coding" - it seems to me like all of the above systems can be combined with colour coding. May 22, 2017 at 21:36
  • 1
    I disagree with the positive evaluation of geographical naming. First, any time a line is extended, the line name either changes or becomes less meaningful, both of which are negative for users. Second, knowing the final destination is rarely helpful unless the line actually follows a straight path (and even then it hinges on knowing the location of suburbs that you might never want to travel to and that just happen to be on the extrapolation of your trajectory). Third, toponyms can be long and hard to remember if you don't already happen to know them. And lastly/fourth, geographical names ... May 22, 2017 at 21:42
  • 1
    ... taken from final destinations of lines can become very confusing if there is more than one line between a given pair of locations (with different intermediate stops), or if not all trains of a line cover the entire length of the line (e.g. when only every second train serves the outskirt that has a lower passenger volume compared to the central portion of the line). May 22, 2017 at 21:43
  • @O.R.Mapper I'm saying that it provides more information that the other systems, it has an additional dimension. I'm not saying that it covers all bases and provides an airtight solution. It's more helpful than the others, it's not perfect. May 23, 2017 at 5:24
  • "It's more helpful than the others, it's not perfect." - the observations I listed, especially #1 and #3, lead me to the conclusion that geographical naming is actually less helpful than the others. May 23, 2017 at 6:42

I think the right way is to combine different methods:

  1. Color coded is my favourite, but it is limited because when there are 15-20 lines, could be difficult to code each line. Besides, it's not a completely accessible way, is not usable by color blind.

  2. Lettering + Numbering: Milan for example uses the code: M1, M2, M3 for metropolitan train. S1, S2, S3 for suburban areas.

  3. Geography based naming. I think could help only people that knows the city and could be confusing for others.

In my opinion the best solution is that grant to the user the shortest and more memorizable instruction, like:

- Line 1, direction Rho, third stop

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