[davismwfl]

You are correct, not every car needs to be modified. Generally engines are the primary modification, as is the CAD systems that must accept extra data and pass it to the trains. Things like hotbox detectors that can count trains axels, determine direction plus the switches and track occupation signals need to also be sent from the CAD (which already receives them in controlled territory) to the locomotive itself.

As a point, PTC works in both dark territory and controlled territory, because it focuses on the train itself (but it isn't as reliable in dark territory). Yes in controlled territory it has greater information but it doesn't require every switch to be modified. Even back in the late 90's every controlled switch reported back its status to CAD extremely quickly and CAD could control the switches remotely. Yes, dark territory is different, but PTC had some benefits even in dark territory. It was the long term goal to have near zero dark territory where a switch, siding or other similar factor would be able to cause a collision.

And just as a point, even when a train leaves one CAD controlled territory (say Union Pacific territory) and enters another (say ran by BNSF) the CAD operators hand off control, much like air traffic control. So the issue of interoperability is minimal as it already is in place in at least a fairly common form. Not saying it isn't without fault or couldn't be better, but the world doesn't have to change overnight, just keep making progress on each part making it better and better.

[paddy_m]

I assume by CAD you mean Computer Assisted Driving? What exactly is a dark area?

What are the differences between the US PTC systems and the systems used in Europe?

[davismwfl]

Computer aided dispatch. Essentially all trains are monitored via control centers owned by a few of the larger railroads. Passenger traffic is even handed off through these centers when crossing the territories.

And yes dark territory is what they call the areas that are unmonitored. Usually these are way out in the middle of no where on single track. Most monitoring believe it or not is hard wired and not wireless. For example, hot box detectors which are basically buried on the inside of the tracks monitor a trains bearing/axel temperatures and can report if one is over heating. This is critical because it is a source of derailments. Those boxes though usually are wired directly to lines running along the track and back to a common point. In many cases a number of lines terminate at one location and are fed to radio towers that beam that data back. In other cases it follows the fiber all the way to a rail yard or dispatch center.

I can't say now what the differences are with PTC in Europe, but I know when I was at GE we looked a lot at what they were doing because in most cases they are far more serious about their railroads.

[lstamour]

I think dark territory means unmonitored sections of track or switches (to be more precise, I guess), that which isn't yet hooked up to the system to watch for speed and other issues that would cause accidents? New to me too :)