[jsmith45]

Block based automated signaling can technically be implemented as a primarily local system. Each block needs to know if there is a train in itself block (in which case all block entrance signals must show stop, and approach signals indicate that they can be entered, but the train must be slowing, so it can come to a stop by the block entrance signal). It must also know about a few preceeding blocks for each path leading into it, so as to know which contain trains that might be trying to enter this block, so it can select at most one to be given the proceed signal, and others to be told to brake to stop in time for the entrance signal. While it is nice if it knows the intended routes of each train so it can favor giving the proceed indicator to a train that actually wants to enter it, but if it lacks that information, then giving the indication to a train that will end up using points to take a different path doesn't hurt safety, just efficiency.

Of course, centralized signaling is better, allowing for greater efficiency, helps dispatch keep track better track of the trains, makes handling malfunctioning signals a lot safer, among many other benefits. But it doesn't mean local signaling can't be done.

[wrs]

Yes, block based signaling is what I interpreted “local first” to mean in this context. It works, but it slows everything way down.

I don’t know, but I would imagine, there’s still a block based setup as a failsafe backup in most or all modern rail systems.