CBTC stands for Communications Based Train Control, or PTC for dark territory. I have only heard of systems that "talk" between the field and the base, due to the vastly increased level of complexity introduced by having field to field comm that must also be mirrored to the base in an effort to avoid unexpected situations in the field (overlap authorities, misaligned switches, so forth)
CBTC utilizes moving blocks, but they are also part of any non-signaled authority system that utilizes Track Warrants, Form D's, or whatever the RR chooses to call them. Instead of a series of defined block limits that do not change, and whose use can be somewhat restrictive when multiple trains and/or MW personnel are introduced to a single line, moving block allows the dispatcher to define the limits of each train/foreman's authority, be it 60 miles, or 1/4 mile, as needed to fit the operational needs of the given moment.
EDIT! Forgot about the last part of the question about any current systems that use train to train comm to establish authority. GCOR allows "Radio Blocking", which sets up communication between two trains, one following the other, and allows the leading train to call clear of locations to the following train, instead of dealing with the dispatcher. Not sure about NORAC, I haven't had that class in awhile and I forget if something similar is allowed. The RR I work for doesn't allow radio blocking, we usually don't have enough traffic on any one line at one time to justify the added expense of another form, or the added level of risk from partially pulling the DS out of the mix.
DSLE to the stars!
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Jack Donaghy wrote:I'm already not liking some of these people, reminds me of being on the bus