how hard is it to put a location based speed governor on the train instead of using antiquated mechanical signals to enforce max speeds? or is that just too much common sense for the MTA?
It would be extremely difficult. How would the train know where it is? GPS is unusable at that depth. You'd need location beacons...but at that point you're better off just using signals, like they already are, rather than upgrading every train and dealing with the ongoing maintenance of making sure that each train's location-based speed governor is properly up-to-date with all proper slow-down locations.
Could you please explain why positioning would be hard? Since trains only move on the edges of a fixed graph, you'd think positioning would be super easy compared to almost all other indoor positioning applications.
It is hard because it must be vitally accurate. Screw it up and you end up with collision hazards. The number of dimensions is not the problem. The safety is.
Your indoor positioning applications would require the installation of numerous positioning beacons--or in other words, significantly more hardware than the many thousands of speed signals they have already installed and are unable to maintain.
MTA is doing this. It’s the basis of Communication Based Train Control.