STrRedWolf wrote:Which I think would be a goal of PTC, to be a third layer of cab signals, would it not?Without getting too deep, PTC is a system that attempts to make sure that the other layers are being followed. Approach a permanent speed restriction (such as the curve in Washington State) and the system makes sure the train slows down before the restriction (regardless of signals displayed). Pass an approach signal and the system makes sure the train follows the rule that applies to that signal (such as an immediate reduction in speed as well as prepared to stop at the next signal - at a location known to the system). Temporary restrictions can also be added so the train slows or stops as required by those restrictions.
I would not consider PTC cab signalling any more than I would consider an alert, informed conductor as a cab signal. Consider PTC as an alert, informed, non-distracted conductor in the cab ready to take action to safely operate the train. Something that if present and activated could have prevented a growing list of incidents, accidents and fatalities. Including the Cascade wreck. We need to have no more preventable incidents.