If you are looking for a means of transportation inside the domes, then bicycles is the right call. If trains are already overlooked, bikes then are nearly completely neglected. They are relatively cheap to produce and basically don't need infrastructure. They also don't need energy to operate and if the dome is only 1 km in diameterthen everything is reall close. 548
The reduction of friction also helps, and the people are kind off forced to exercise, what is good in space, people in low G really need to exercise. They are also really small, something good in the crowded place that the people live.
I remember reading somewhere that bikes are being used in those big airports here on earth because of those features, and that they are a really smart way of moving if we ever go to space, but I could not find that report (maybe it was a video, possibly vsause or something like that) anywhere, sorry for that, if anyone finds that out, please show me, it makes a long time I've seen it.
The biggest problem with trains is the cost to make the rails and the amount of metal you have to put on them ,something that is still not a lot compared with other means of transtortation. If you need to have these big resourses coming and going, the trains are the best option indeed, but if what you look for is people's mobility, bikes are just fine.
The thing with using bikes to dome-to-dome transporation is how far would you have to travel and the fact that you would need to make highway-like bike path, but since you only have 20 domes 2 miles apart each, if you put the in line and run trough end to end, you would have to go trough 82 km (38 miles = 62km, pluss the distance inside the domes), a lot but still possible. If you were not to put them in a line but instead in any oyher shape (two lines, three lines, triangles, hexagons,...) the maximum distance you would have to travel would decrease a lot, altho you would have to build more roads. You can find the mid term that is best for you. 461