>>1831679>>1833010We have some roadside rail lines in Switzerland, but they're all from back in the day when road vehicles were quite primitive and few people had cars. From a planner's perspective these are pretty awful, since they cause all kinds of interference with road traffic with constant level crossings that can't be overcome, and they're hard to double track as well. But at least they have the advantage of having segregated infrastructure. Putting rails into the street would be a terrible idea, it makes road maintenance much more difficult and expensive, and the rail line isn't segregated from vehicle traffic, so your train may get stuck behind a tractor going 20 kph for a while and get thrown of schedule, while a bus can overtake it.
I don't think some interurban-style roadside rail line is actually all that unrealistic, so long as there's at least some demand, and it could be used for short line freight like back in the day, connecting to the mainlines. But the possibilities for such lines would be limited and dependent on the region not being completely car-dependent, so that you can have connecting services, also comparatively expensive.
