We're talking about the track system here, not the trains. For trains it makes of course a lot of sense to use modern locomotion control technology. However wh

We're talking about the track system here, not the trains. For trains it makes of course a lot of sense to use modern locomotion control technology. However when it comes to the tracks and signaling, there's only very little to be gained to have the actual signalling being computerized on a standard two track railway with the occassional switch track. The distance between trains, both in time and space, is determined by the blocking of the tracks. There's a hard constraint on the minimum distance between blocks: For any given train running a track, it must be able to come to a full stop within the length of a block. And for safety reasons there must be at least two free blocks between trains (exercise to the reader: why two blocks? Hint: Emergency braking). Now there is of course the possibility to subdivide a track into microblocks, where a fixed number of microblocks make up a "block" and the "block" borders are dynamically moving along with the trains on a track, so that there's always two blocks of distance between them. But again, this does not require a programmable computer to implement. It can be done using hardwired circuitry (and I'd feel much safer using such a system); just throw a few 74HCT… ICs onto a PCB and mass manufacture that.