Shield generation for railways

[jteresco]

I'm not sure what would be appropriate in general here, but the ones we get now are pretty ugly.

Is it good enough to have a generic London Underground for those routes, a generic MTA for NYC subways, etc. and let the text below differentiate?

[si404]

There's a lot of the service/line bullets/logos on wikimedia commons that would cover a lot of the more local systems across the planet as well as most of the continental European regional rail ones. There's also a few for anglophonic regional rail routes, but I don't know how many are hobbyist designs.

I've included Paris and the London ones I would like in the relevant threads.

A big problem with the shield generation is that the background colour changes from line to line, so the more automatic method used for roads wouldn't work (eg Paris 1 is yellow, 14 is purple; NYC 123 are red, NQRW are yellow, etc).