NS cab signaling questions

[.Taurus.]

Hello
I have some questions about the cab signaling system that NS use:
(Especially after reading the NTSB accident report of the New Brighton, PA derailment in 2006)

[...] At Elkhart, Indiana, the first NS crew change point, an NS locomotive unit equipped with cab signals was added to the head of the train. [/...]

[...] Cab signal units display the governing signal indication in the cab of the locomotive. The territory where the accident occurred utilized cab signals; it was not equipped with wayside signals except at control points. [/...]

[...][footnote] Signals: Train movements through the area of the derailment were governed by signal indications of a traffic control system controlled by a computer-aided train dispatching facility under the direction of the NS Cleveland Line train dispatcher at Greentree, Pennsylvania. The system primarily used cab signals (signal indications displayed in the cab of a train’s lead locomotive unit); no wayside signals were present except at control points. [/...]

That's new for me, didn't know that before, so I need some help to understand that

What does control point mean ? Where the actual cab signaling block ends and another one begins ?
So there is only one cab signal block between two control points and the cab signal repeat the aspect of the dedicated wayside signal onto a device in the locomotive cab.

Or is it possible to have cab signals without the dedicated wayside signals ?



But how do the engineer know where one cab signal block ends and another one beginns.
Normally between two blocks a wayside signal is located, but when the wayside signals are missing, how do the engineer for example know where to stop ?
( Scenario: The cab signal of train [A] shows "stop" because the next block ( infront of the train [A]) is occupied by another train , which cab signal shows "proceed" . Now the engineer of train [A] miss the control point and didn't stop in his cab signal block and rolls into the cab signal block of the train . Now the cab signal of train [A] suddenly shows "proceed", which is orginal dedicated to train and so the disaster run its course. Is this a realistic scenario ? )

So did they place for example signs at these locations where the cab signal block changes ?

--

The cab signal based on the PRR system, right? Did NS change much over the years or is it still the same system which PRR used ?

Greets

[jgallaway81]

1) the terms "control point" and "interlocking" are pretty much interchangable these days. technically, a "control point" is any point where the dispatcher can force a specific signal indication... safety first requires that a dispatcher can only "force" a stop signal or release the signal to operate as per standard automatic block rules. the "CP' is used when the interlocking is not controlled by an onsite tower... ALTO tower controls Alto interlocking, so its not a CP, but Homer interlocking is also controlled by ALTO, but because it doesn't have its own tower, it IS CP-Homer.

2) Cab signals without waysides is a legit operational setup. In addition to a portion of Pitt Div Conemaugh Line, the entire HBG Div Morrisville line is cab signals without waysides. Cab signals can't display a 'stop signal' so thats why the waysides MUST be displayed at the interlockings. (as well as for the few rare permitted movements that operate sans cab signals)

As for your scenario, it can't happend because the cab signals are transmitted through the rails. if there is a train ahead of another train, the axles shunt the rails, killing the cab commands and the cab signal will display restricting.

Regarding your question about knowing where one block ends and the next begins is moot because the engineer must operate the train according to the cab signal indication regardless of where his train is (conversant with good train-handling issues).

The cabs do give the engineer a heads up when he is approaching an occupied block, displaying an approach in the cab, just as it would display an approach on the wayside.

[kbcm721f]

NS has not changed anything from the original PRR standard. Something interesting, the EL cab signal systems NS runs operates on 32VDC; this is leftover from the steam days. Yes PRR ran cab signals on there Steam Engines