As far as Orville goes, the diagram is for an interlocking, in pre-CP daysof the PRR. To see what would have been done vis a vis CP's, just find a timetable for CR or whatever railroad now operates it and see what they did. It could be one CP or it could be 4 CP's. If one route went to the NS and the other to the CSXT it could be one CP on one railroad and 3 CP's on the other or it could be one CP on each railroad.
In the 200 miles between Dexter, MO and N Little Rock, AR on the UP there are 49 CP's at 37 stations and zero "towers" There is one interlocking, but its not a CP and there are 8 stations that don't have a CP associated with them.
Dave H. Painted side goes up. My website : wnbranch.com
do i need to know anything about CPs in order to understand/develop a CTC panel or signaling system?
now it sounds like a CP is simply a milepost on a RR
greg - Philadelphia & Reading / Reading
gregcnow it sounds like a CP is simply a milepost on a RR
A CP is "the location of absolute signals controlled by a control operator." (GCOR 2010). A milepost won't have controled signals.
gregcdo i need to know anything about CPs in order to understand/develop a CTC panel or signaling system?
If you are modeling pre-1985 or so then CP's weren't defined in the rules. If you are modeling post-1985 or so, they were. If you are modeling pre-1985 then no.
The CTC will be essentially EXACTLY the same in either case. If you are modeling pre-1985 then the interlocking at Birdsboro would be called the interlocking at Birdsboro and would be manually operated by a tower at Birdsboro, then later an operator in the Tower at Oley, then eventually post 1985 would be CP Bird. The signal system would work exactly the same in any case (except maybe the controls would be located in different locations and type of control might have been upgraded or changes in the rules over time) for the trackage that was common in the various eras.
Take the switch at the east end of the siding at Bess near MP 25, which is in CTC.
Pre-1985 it would be called the "east switch at Bess". The would be an eastward signal on the main, there would be a westward signal on the main and a signal to come out of the siding. A dispatcher or operator would control the signal (and switch). It would not be an interlocking.
Post-1985 it would be called the "CP A025". The would be an eastward signal on the main, there would be a westward signal on the main and a signal to come out of the siding. A dispatcher or operator would control the signal (and switch). It would not be an interlocking.
The only thing that changed by calling it a CP was the name. EVERYTHING else is exactly the same. The signals work the same, the switch works the same, who controls it is the same, it gives the same indications, the signal logic is the same.
If you ask a signal engineer about a CP he will describe how it works because a CP is what they call that location. If you ask me what goes on at a CP that is the end of a CTC siding I will tell you how the end of a siding works. If you went back to 1975 and asked the same question in CTC I would give the same description except I wouldn't necessarily describe it as a CP. The magic isn't in the name CP, the magic is in the fact that it's the end of a siding.
I think CPs are generally named after nearby mileposts. On MetroNorth, the Hudson line CPs are named after the mileposts, on the Harlem Division they add a 1 in front of the milage figure, and on the New Haven line they add a 2 in front of the milage.
Simply put, a control point is any signal that is controlled by the dispatcher. A CP is a STOP signal. If the signal displays STOP, you must get permission from the dispatcher to pass it while it is displaying the STOP indication. A CP has a name.
Signals with numbers are "Intermediate" signals. These signals display "Restricting" as its most restrictive aspect. Meaning a train can pass the signal at restricted speed without having to contact the dispatcher. They are not controlled by the dispatcher. Instead, they are controlled by the signal system. When the dispatcher sets up a "current of traffic" by lining up the Control Point, the aspect of intermediate signals will follow accordingly.
If the dispatcher has not set up a current of traffic, intermediate signals between two control points will show aspects indicating the condition of the block ahead. This could mean that with enough signals between two control points, you could go out into the field and see a set of signals side by side displaying "Clear" in both directions. Once a current of traffic is set up, the opposite signal will go to a restricting aspect.
One other thing to keep in mind and this is very important, the dispatcher CANNOT and DOES NOT give a train a Clear signal. The dispatcher has no idea what aspect is displayed to the train crew. The "SIGNAL SYSTEM" is what provides the aspect shown according to the track conditions ahead! The dispatcher can only tell the signal system what he wants done.
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No. The key word in "control[led] point" is "control".
It's a location where the dispatcher controls signals (and usually turnouts, but an CP can have zero turnouts) in order to control train movements in CTC. Turnouts and signals will be interlocked to prevent conflicts.
If there's nothing there to control, it's definitionally NOT a control point.
Chris van der Heide
My Algoma Central Railway Modeling Blog
I have always considered a 'control point' to be a location on a ROUTE where train position is determined and permission to proceed further given.
It is not material what type of equipment is used to convey that authority; the 'point' is spatial.
How CPs are practically implemented would, of course, vary by railroad, and there is a variety of 'safe' options to determine exactly where on a given railroad or route the "functionality would be implemented". But arguing about the size or predilection of the angels dancing on a particular pinhead does not determine why the pin is there in the first place.
cv_acrIf there's nothing there to control, it's definitionally NOT a control point.
That's why an automatic interlocking isn't a control point and often doesn't even show up on the dispatch panel. There is nothing to control there.
OvermodI have always considered a 'control point' to be a location on a ROUTE where train position is determined and permission to proceed further given.
BigJim Overmod I have always considered a 'control point' to be a location on a ROUTE where train position is determined and permission to proceed further given. Not so on CTC.
Overmod I have always considered a 'control point' to be a location on a ROUTE where train position is determined and permission to proceed further given.
Not so on CTC.
Well, yeah, it is. CTC control points (dispatcher controlled signals) are where the dispatcher controls the signals to give the trains their permission to proceed.
I'm not sure how you'd argue that it's NOT a location where permission to proceed further is given. It's absolutely the point where a train will stop if it doesn't have permission/signal indications to go further.
A control point doesn't need to have switches. There are control points that are only controlled absolute signals. They don't even have to have CTC on the territory. Some are, or were, tied into train defect detectors, often called hot box detectors. If a train tripped a detector, it holds a specific signal at STOP. It has to be manually be cleared by the control operator. In our timetable, they appeared as "Hold Signals."
Being controlled, such signals could also be used by the control operator as end points to on track authority for MOW/signal people.
We also used to have "Hold Points" on the exCNW across Iowa before CTC was installed. It was even before wayside signals were installed. The control point consisted nothing more of a sign saying "Hold Point." Instead of causing a wayside signal to be red, it shunted the block causing the cab signal to go to restricting. The sign appeared at the end of that block and a train couldn't pass the hold point without authority.
Jeff
Or.... its the very simple definition given in the rule book. A location where there are controlled signals.
Nothing more, nothing less. You can have a control point that doesn't determine occupancy or route (other than "past this signal").
cv_acr BigJim Overmod I have always considered a 'control point' to be a location on a ROUTE where train position is determined and permission to proceed further given. Not so on CTC. Well, yeah, it is. CTC control points (dispatcher controlled signals) are where the dispatcher controls the signals to give the trains their permission to proceed. I'm not sure how you'd argue that it's NOT a location where permission to proceed further is given. It's absolutely the point where a train will stop if it doesn't have permission/signal indications to go further.
On the New Haven line, some former interlocking stations (interlocking/signals + tower + tower operator) were converted to "controlled points" (controlled by the dispatcher in New York City) when the signal system was upgraded in the 1980's.
As part of the transition, older interlocking machines were upgraded to modern ones, often with a smaller model board, with a "local-remote" toggle switch.
One moment, the switch was at "local", and the interlocking was under the control of the operator. Then... flip the switch... and it transformed into a "control point" controlled by the dispatcher. Thus, a former interlocking like "Central" (Central Avenue, Bridgeport) became CP257 with a general order and the flip of the toggle switch.
If something went wrong... it was a simple matter to "throw the toggle back" and re-assume control of the interlocking at the local level. Seldom done, but possible.
Since then they've built several brand-new control points, no tower, just a bunch of signal boxes to house equipment. I believe some of these (if not all of them) have some kind of "model board" inside, so that signal maintainers can take over with "local control" if absolutely necessary in an emergency.
But really, this entire discussion shouldn't be too complicated. Who controls what and where is one of the basic things one learns when one goes working "out on the territory"...
Not too complicated, ha:
In land surveying, civil engineering, and railroad engineering, the term "control point" has a completely different, and very literal, meaning that has nothing to do with signals. Since the original post did not specify, my mind immediately goes to the engineering and survey definition:
A point which has been set and established by known or assumed coordinate system and known or assumed elevation. Said point is used as a reference to "control" other survey points or elements within a project.
https://static1.squarespace.com/static/5ced5c75c2950300016355c0/t/6125b755efceef50ddc7eebd/1629861718104/ECI+Control+Points+Asset.pdf
Overmod https://static1.squarespace.com/static/5ced5c75c2950300016355c0/t/6125b755efceef50ddc7eebd/1629861718104/ECI+Control+Points+Asset.pdf
That's cheating!
When I learned surveying back in the late 60s, we had to set our control points using transects from USGS monuments or take star shots. All we had were transits and chains. We were in hog heaven if we could use a Theodolite. The folks in the mid-west and west had it slightly easier if they could transect from a section corner.
Ray