ACSES-2, ITCS, and PTC

[aegrotatio]

I read an article in the magazine recently that states that ACSES-2 is compatible with certain other roads' PTC systems.

What keeps us using ACSES-2 elsewhere? I understand that ITCS is used in Michigan, but is it in any way related to or compatible with ACSES?

[oltmannd]

ACSES, ITCS and PTC are all pretty different.  There's not much equipment that can be shared between them.  

ACSES is cab signal based, primarily, with some fixed track transponder secondarily.  The train only needs to know it's relative position to the track transponders and track circuits.

ITCS is strictly a local radio-based system that relies on each block signal "talking" to the train directly.  There is no central movement authority piece.  The train has to know where it is in relation to the fixed signals, though.  Movement authority comes from the train dispatching system  "normally".  

PTC has movement authority coming from a central system via radio directly to the train.  Communication is all done through a central system the interprets and routes the messages.  Like ITCS, the train still has to know where it is.

A "compatible" system might share antennas and possibly a data radio, and some part of a display, but everything in between would be different.   It would be a rather costly deal...

[aegrotatio]

Thanks. Some of the controversy involves radio spectrum availability. Can't PTC use coded track circuits?

[oltmannd]

Sure.  Coded track circuits exist where there is no cab signal.  But, you still need to tell the back office  about block occupancy - so it can allow the next train, so the need for radio still exists.