Lingua Franca predates colonialism. Latin predates Lingua Franca, although one can argue Latin was forced down due to the Roman Empire's extensive reach and size. Ancient Greek also served a similar role. One doesn't need to learn each others language as long as they all know one common language. One could argue for Esperanto, or a purely symbolic language like traffic icons, but you need to learn that one too. So it makes more sense to use a fit for purpose language for travel that has no ambiguities. You can even create a graph that can be queried. There's all sorts of ways to solve this with as little pain as possible as long as you care to. And wanting people to just learn the local language to traverse a transport network is chauvinism.

If you visited Japan as a tourist, I believe you learned enough to say hello, ask someone where your hotel is, and so on. I don’t for a second believe you learned enough to understand arbitrary train network change announcements. Unless you spend years studying the language before visiting any country as a tourist, which would be absurd.