Overmod https://static1.squarespace.com/static/5ced5c75c2950300016355c0/t/6125b755efceef50ddc7eebd/1629861718104/ECI+Control+Points+Asset.pdf
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
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.
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"...
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.
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.
.
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.
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").
Dave H. Painted side goes up. My website : wnbranch.com
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
Chris van der Heide
My Algoma Central Railway Modeling Blog
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.
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.
gregcnow it sounds like a CP is simply a milepost on a RR
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.
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.
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.
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.
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
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.
gregcso a CP is not simply a signal, but a group of signals, switches and tracks under the control of a single tower, for example.
No. A CP is "the location of absolute signals controlled by a control operator." (GCOR 2010).
There is no requirement for switches, there is no requirement for a "tower". There could be, but there doesn't have to be. Probably 90-95% of all the CP's are just one end of a siding. No towers, just one switch.
The KEY is that there is a location with a manually controlled signal or signals (see GCOR). There can be lots of other stuff, but what defines it is there is the manually controlled signal.
An interlocking may be a CP or it may not.
A CP can be in CTC or it may not.
That's why I keep saying don't read more into a CP than is there.
In my defense. I know the ICC investigations is no more. I found the archives from the NTSB web site. From 1911 through 1965. There is some good reading in the reports and one can spend an entire night just skipping through. I don't know if it's the NTSB or the National archives that maintains the list. I believe it is the National archives. It could be the DOT even. Whoever maintains the list I found it through the NTSB's website.
Pete.
dehusmanOnce again, don't read more into a CP than is there.
unfortunately, there's not much to read
so a CP is not simply a signal, but a group of signals, switches and tracks under the control of a single tower, for example.
dehusman wrench567 They are always listed as manned, or open. Most read like " train xxxx past so and so interlocking tower which is the last manned control point." Or " train xxx passed through signal xxx which is the last open control point." While these examples come from steam era reports, Be careful with eras here. In the steam era, CTC (rule 261) was not as common as it is today, and "control points" were not defined in railroad rule books. One also needs to remember that there won't be any "steam era" NTSB reports since it wasn't created until 1967, well after the steam era. Any truly steam era reports on accidents would probably be ICC reports. One also has to remember that the signal and control systems, the actual design, operation and, maybe most importantly, communication systems were vastly different in the steam era than in a more modern era, so the concept, definition and function of a control point might be different.
wrench567 They are always listed as manned, or open. Most read like " train xxxx past so and so interlocking tower which is the last manned control point." Or " train xxx passed through signal xxx which is the last open control point." While these examples come from steam era reports,
Be careful with eras here. In the steam era, CTC (rule 261) was not as common as it is today, and "control points" were not defined in railroad rule books.
One also needs to remember that there won't be any "steam era" NTSB reports since it wasn't created until 1967, well after the steam era. Any truly steam era reports on accidents would probably be ICC reports.
One also has to remember that the signal and control systems, the actual design, operation and, maybe most importantly, communication systems were vastly different in the steam era than in a more modern era, so the concept, definition and function of a control point might be different.
Thank you Dave, I tried to make that point early on.....
Sheldon
gregcif you were adding CTC/signals to your layout, how would you identify the CPs?
You are kinda going backwards. A control POINT is a location. Its the signal equivalent of a STATION.
Orville could be just one CP.
Once again, don't read more into a CP than is there. There are all the rules and operational considerations for interlockings and for CTC. There are NO "CP rules". Don't attribute stuff that is a CTC, interlocking or general signal design thing to a "CP". A CP is designated to identify a group of locgically and operationally connected switches and signals.
wrench567They are always listed as manned, or open. Most read like " train xxxx past so and so interlocking tower which is the last manned control point." Or " train xxx passed through signal xxx which is the last open control point." While these examples come from steam era reports,
Can I toss some gas on the fire?
Reading archived accident reports from the NTSB, there's always a mention of the last control point. They are always listed as manned, or open. Most read like " train xxxx past so and so interlocking tower which is the last manned control point." Or " train xxx passed through signal xxx which is the last open control point."
While these examples come from steam era reports, one has to assume that control points were manned stations, towers, or platforms where train orders, and signals were given to direct train movements over a section of the railroad. Either a block, branch, yard, or station. I could not find the glossary of terms or definitions on the NTSB's website.
gregc if you were adding CTC/signals to your layout, how would you identify the CPs? or is it more about defining the interlocking logic that the CTC system uses to determine the signal indication based on actual switch position, CTC signal lever setting and block occupancy of associated trackage?
if you were adding CTC/signals to your layout, how would you identify the CPs? or is it more about defining the interlocking logic that the CTC system uses to determine the signal indication based on actual switch position, CTC signal lever setting and block occupancy of associated trackage?
Exactly - define what the interlocking needs to do, and that will establish the control points, not the other way around.
gmpullmanhttps://ekeving.se/ctc/us/NYC_RS_1927.pdf
thanks again Ed
dehusmanNORAC 2003 : A station designated in the Timetable where signals are remotely controlled from the control station. GCOR 2010 : A location of absolute signals controlled by a control operator. The term doesn't appear in the half dozen or so rule books I looked at that dated 1980 or earlier.
GCOR 2010 : A location of absolute signals controlled by a control operator.
The term doesn't appear in the half dozen or so rule books I looked at that dated 1980 or earlier.
The CTC system would allow the flow of traffic to be set over many sections of track by a single person at a single location as well as control of switches and signals at interlockings, which also came to be referred to as control points.
The majority of control points are equipped with remote control, power-operated switches.
the following from Orville Interlocking Tower might be a good example to consider
gregccoming to the conclusion that it's nothing more than a remotely or manually operated device such as a signal or switch. i've been given the impression that it was much more than a signal, a route between signals in a interlocking/signaling system
As has been said several times, a control point is a controled signal (per GCOR and Norac definitions).
The reason you have controled signals is you want to control trains operating over switches or on different routes. So yes there will commonly be switches associated with a CP and where there are switches there will be multiple routes.
CP's come in all sorts of shapes and sizes and histories of how they got there. There is no one simple description that covers every option in detail. In the modern era the line between CTC-CP-Interlocking gets blurred somewhat. Prior to the 1980's the term CP wasn't used, CTC and interlockings had different rules (very similar but with some differences).
Don't make this more complicated than it is.
NHTX I don't ever recall hearing the term control point used on any place but along the east coast.
Nope, they are used all over the country. The UP and BNSF have hundreds, if not thousands of them. And the majority weren't interlocking towers previously either, some were but there are way more that were created when the lines were CTC'd. The term CP really took off when the NORAC and CGOR rule books were written.
A "controlled point" is generally an interlocking that is operated from somewhere else.
It might even be nothing more than a signal controlled remotely by the dispatcher (even though there are no switches associated with it).
A CP generally isn't going to have "manually operated" switches -- how would the dispatcher or operator throw them from a remote location?
Now and then, you WILL find a manual switch within the limits of an interlocking, but it will be thrown by the members of a train crew, after receiving permission (or "the unlock") from the dispatcher or operator.
Examples of controlled points might be CP 72 and CP 75 on the Metro-North Hudson line, south and north of Poughkeepsie.
An example of a controlled signal would be found north of Hudson station on the Hudson line, governing southward movements. I can't remember if they actually made this "CP 115" or not, it's been too long since I was there.
I recall a manually-operated switch in the middle of CP 89 (just north of Rhinecliff) on the Hudson line, that once connected to the old CNE. Again, it's been a long time, 30 years since I worked up that way.