Forgot another one of the idiot "expert's" claims - that the railroads had no excuse for installing the technology by now because it has existed for more than 50 years.

Yes - there has been simpler types of train control but I think they have actually been in use for more than a century. Whether it is ATS, ATC or CCS they have been around for a long time, but they typically only enforce (continuously or intermittently) the signal indications. And to my limited knowledge, most of the systems will only stop the train if the engineer fails to take action to slow or stop the train according to signal indication, and in many cases can simply acknowledge the system and continue on the same or restricted speed depending on the situation. I know the New York subway system still uses a mechanical trip system to put a train in emergency that passes a red signal - I wonder how many years that system dates back?

The PTC being mandated by Congress is much more - it is a GPS, radio based communication system controlled by extensive software. It not only enforces signal indications, but also enforces main track authority including limits of occupancy, speed limits, temporary slow orders and Form B's. In dark territory it must protect against open switches, and I believe establishes a limit how close it can get to conflicting movements. And there is a complicated algorithm that the system uses to stop or slow the train theoretically in time. And best of all - the mandated system still doesn't work due to unresolved software, hardware and regulatory conflicts!

Funny that the Northeast Corridor uses a older different system that is not compatible with the new PTC. The NEC system followed the European practice of using in track radio tags to determine location instead of GPS, no doubt dating back to when GPS was intentionally inaccurate to the point in early tests GPS couldn't determine which track the train was on.