There seem to be a fair number of commuter train lines that do this, but I don’t really consider a train to be the same as an urban tram/bus system. The latter has orders of magnitude more daily passengers, and it’s a far wider breadth of people compared to the typically better-off suburban commuter lines.

And as someone that’s ridden the bus in LA many times: the culture of acceptable behavior there is infinitely lower than the typical Central European bus.

To be fair I did have NYC in mind when writing the comment though, and I should have looked into west coast systems more.