Serious Signal question....

[CNW_6000]

How about this then: on the CN mainline north of Oshkosh there’s several sets of signals. Some face north and some south. For those familiar with the area they are by HWY Y and Snell Ave. Those signals are almost always showing red all the time, every day. I discovered this when I was driving past looking for a SB train and saw the signal as red. I waited for 2 hours and eventually headed up to Neenah where I found the train. Neenah is 8-9 miles north of Oshkosh. Nothing headed south, nothing headed north. Why would the signals remain red 24/7/365?

Anybody on this one?

[kenneo]

How about this then: on the CN mainline north of Oshkosh there’s several sets of signals. Some face north and some south. For those familiar with the area they are by HWY Y and Snell Ave. Those signals are almost always showing red all the time, every day. I discovered this when I was driving past looking for a SB train and saw the signal as red. I waited for 2 hours and eventually headed up to Neenah where I found the train. Neenah is 8-9 miles north of Oshkosh. Nothing headed south, nothing headed north. Why would the signals remain red 24/7/365?

Anybody on this one?

This is a CTC controlled Interlocking. By FRA Rule, unless approach lighting is authorized, all signals governing entry into ANY Interlocking MUST display STOP 24/7 unless entry has been authorized by the Control Operator. I know of no authorization for approach lighting to an interlocking unless the approach segments are under “Positive Control” track circuits --ie CTC.

[CNW_6000]

How is a single mainline with a passing siding or a paralell main considered an ‘interlocking’?

[Anonymous]

Once you understand what is happening, it is really quite simple — so now for the complicated description.

[snip]

To have the signal you are talking about stay dark in your situation would take almost as much contol circitry as is there now to operate the signal. You would need either a huge number of control relays to interlock the indications so that everyone is properly protected or you would need a “predictor”, a small computer (seems they always want to run on Windows), and about twice as many signal maintainers to keep that system in operation.

Thanks for the detailed explanation, Eric. The above paragraph makes the most sense to me as to why the light comes on when it’s really not necessary. I didn’t realize signalling systems could be so complicated. But the reason why it comes on now makes perfect sense.

[kenneo]

How is a single mainline with a passing siding or a paralell main considered an ‘interlocking’?

By definition and function. Normally, when one says “interlocking”, the standard picture of a tower and intersecting lines comes to mind. This is, in fact, your basic definition.

However, with all “Positive Control Points”, the FRA requires that all routes and signals be interlocked, just as in your standard definition of an interlocking, and interlocked in the same manner for each type of interlocking. Therefore, a CTC switch and signal are called a “Control Point”, operated by a “Control Operator” (could be a dispatcher or towerman or ???), and fall under the definition of interlocking. They are inspected and maintained in the same manner.

Complications arise because a true interlocking plant is a stand alone operation. CTC is not. It is an interlocked overlay of an ABS system, operates as an ABS system BETWEEN Control Points, and as an interlocking AT Control Points, often at times with adjusted interlocking rules such as permitting approach lighting.

Dan, I am willing to answer any of your questions that I can, but here I am trying to give an accurate and complete an answer in as simple a manner as possible. So, if I don’t get it for you the first time, try again. You never know!!

[kenneo]

Once you understand what is happening, it is really quite simple — so now for the complicated description.

[snip]

To have the signal you are talking about stay dark in your situation would take almost as much contol circitry as is there now to operate the signal. You would need either a huge number of control relays to interlock the indications so that everyone is properly protected or you would need a “predictor”, a small computer (seems they always want to run on Windows), and about twice as many signal maintainers to keep that system in operation.

Thanks for the detailed explanation, Eric. The above paragraph makes the most sense to me as to why the light comes on when it’s really not necessary. I didn’t realize signalling systems could be so complicated. But the reason why it comes on now makes perfect sense.

You are welcome. Sometimes I have the answer. Glad I could help.

[CNW_6000]

I think I got it that time. Thanks! It makes sense now. It’s amazing what I can learn when I shut up and read, LOL!