Most urban rail networks in the world use color to distinguish lines, either alone or in combination with line names or numbers. Moreover, most of these networks have different train fleets for different metro lines – for examples, the trains on the Northern line are used only on the Northern line, and the trains on Paris Metro Line 1 are used only on Line 1. The interiors of these trains have static line maps dedicated to the lines they serve. Occasionally, the trains are also painted in their thematic colors, as in Boston. So, why not extend this and not only paint trains in their thematic colors, but also have different art on each trainset, using the thematic color?
A blue line, like the Piccadilly line or the RER B, would use drawings that incorporate the color blue in some essential way. For example, one trainset could depict an endless ocean, one could depict the sky, one could depict glass-clad skyscrapers that appear blue, and so on.
The key here is to make each trainset visually distinct and recognizable. Part of the reason is pure art: it introduces more interesting variability to a mundane activity, serving the same purpose as street sculptures. This exists in Japan to some extent, with public mascots and Hello Kitty trainsets, but this could generalize to every trainset. In a large city, this would require finding several dozen different paint schemes per color, ideally each by a different artist using a variety of styles.
But there’s another reason for this scheme: it makes it easier for passengers to remember which train they were on if they lost something or wish to report a crime. Right now, trains are tracked by model number, which passengers have no reason to remember after getting off the train. In contrast, a heraldic system is easier for passengers to retain, especially if the art covers both the exterior and the interior of the vehicle.
For the latter reason, it’s fine to be repetitive and paint every car in a trainset with the same scheme: passengers can roughly remember if they were near the front or back of the train, so if they lost something on the train, they can give enough information to reduce the search space to maybe two cars. Trainsets on modern urban rail systems are almost always permanently coupled, often in open gangways – even New York permanently couples cars into half-trains and joins two sets at a time to form a train, making it feasible to associate paint schemes with entire sets rather than individual cars.
The choice of art should rely on local history, geography, mythology, and culture whenever possible. For example, in the Eastern United States, one red trainset could depict brilliant fall foliage, but in Europe, trees do not turn red in the autumn so the reference would not be easily understood. In Japan, trees turn red in the spring and not the fall, so a red trainset could be painted with the cherry blossom. While Paris does not associate red with the color of leaves in any season, it was historically a center for impressionist art, so one blue trainset could have an impressionistic painting of foliage depicting it in blue.
Iconic food may be another intensely local element to paint in some cities. Everyone in New York knows what a bagel, a New York-style pizza, and a hero sandwich are, and New Yorkers of all ethnic and social groups eat them. At the deli, the professor and the security guard may well order the same pastrami hero. The same is true of döner and currywurst in Berlin, and bento boxes and yakitori in Tokyo.
Mythology and history add more recognizable symbols that are specific to the region or country. London and Paris may each find famous battles to commemorate, just as London names one of its intercity train stations after Waterloo and Paris names one of its after Austerlitz. An American city, especially Washington, may depict Union troops in the Civil War or the raising of the flag at Iwo Jima. Every major city can find an episode of its labor history to paint on one of its trainsets, in red of course. Mythology can add recognizable elements, such as fire-breathing dragons in red, Poseidon in blue, and pots of gold in yellow. Those elements would naturally look differently in a non-Western city like Tel Aviv or Singapore, but the principle is the same.
Diverse cities especially benefit from being able to depict their various cultural backgrounds, making different trainsets more visually distinct. Paris can paint some of its green and black trains with Arabic calligraphy, New York and Chicago can depict black Union troops with blue uniforms, Washington can depict the March on Washington with a blue sky or green lawn background, London can depict the Windrush and lotus art and Muslim South Asian architecture. These cities are all predominantly Western, but have large and growing minorities from non-Western backgrounds or from backgrounds with different takes on Western cultural production (such as black and Hispanic Americans), and should reflect the majority culture as well as the minorities, treating the transit network as a microcosm of the entire population.
Commercial culture and advertising
The plan should be to keep each design for a long time, potentially the entire life of the trainset, or at least through a midlife refurbishment. History, mythology, and geography all provide themes that are sufficiently long-run to remain relevant over the long life of a train.
In some cases, commercial properties can both be expected to exist for a long time and have well-known thematic colors. Examples include Star Wars and the iconic light saber colors, the best-known Pokemon, Hello Kitty, many superheroes, and the Smurfs. Transit agencies could enter long-term advertising contracts with Disney, Nintendo, and other long-lived corporations producing popular culture, and paint their properties on trainsets.
Advertising on the subway has a long history, and can coexist with painting the train if the regular ads are contained to the usual posters. It’s already spilling into painting an entire train: the Hello Kitty train is one example, but negative examples exist as well, when New York wraps an entire subway trainset in an ad for a television show that will be forgotten in a few years.
This kind of long-term advertising, in contrast, reinforces the recognizability of individual trainsets as no two trainsets should ever be painted with the same property (though trains of different colors may be painted with different Pokemon, or one with Jedi and one with Sith, etc.). Moreover, the paint scheme should be stable over 20 years – temporary modifications to help advertise a new film, video game, TV series, or book in the franchise should cost extra, and potentially be treated as regular ad posters.
However, there should be a limit to commercialization: the majority of subway paint schemes should not be based on global brands, but on local factors. Pokemon is everywhere, but the cherry blossom, recognizable skylines, picturesque mountains, and historical battles are specific to a country or region.
Just as cities often have art exhibits at subway stations, and just as they sometimes paint the trains on each color line with the color it’s named after, subway and regional rail networks can paint trains individually in thematic colors. In the largest cities, like New York and London, this could well involve more than a thousand distinct paint schemes; this is fine – those cities have enough artists and enough inspiration for a thousand trainsets.
Overall, the combination of some commercial properties with various aspects of history, geography, tourism, food, and mythology, curated from the majority group as well as from various ethnic and religious minorities, is exactly the mosaic that makes the city’s culture. One of the two prime reasons to do this is as a tool to help passengers remember what train they were on. But the other one is art, which simultaneously is aesthetic and sends a message: on the train we are all New Yorkers, or Londoners, or Parisians, or Berliners.