Restricting aspect question

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Restricting aspect question

Postby MattW » Tue Oct 27, 2015 4:17 pm

As is being discussed in my thread about PTC in dark territory, CSX has replaced all the signals in their Atlanta Terminal Sub for PTC. Once thing I noticed is that any signal capable or showing the restricting aspect is at least G-Y-R over L-R. In a few places where they need medium and/or slow speeds (CP-Kirkwood southbound) they use 4-lamp signal heads, I think G-Y-L-R. My question is why don't they just use a single 4-lamp signal head? I know CSX is big into approach-lighting on intermediate signals, so if their goal is to conserve lamp life and/or energy, then why have a second red lamp that just has to be maintained? I see this same pattern elsewhere, other railroads seem to enjoy putting an entire second head on their signals just to get a restricting aspect.
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Re: Restricting aspect question

Postby ExCon90 » Tue Nov 24, 2015 4:06 pm

I see no one's answered this, so I'll comment that I believe many railroads won't use a single lunar white by itself, to avoid possible confusion with some random white light nearby, but only use lunar together with some other color, usually red.
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Re: Restricting aspect question

Postby MattW » Fri Mar 04, 2016 11:45 pm

Sorry I failed to respond, ExCon, thanks that does make sense. Now I have another related question. Is there any rhyme or reason for which head the lunar lamp will go on? Sometimes it's the second lamp, but sometimes it seems to be the third. Is it some kind of semi-route signaling?
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Re: Restricting aspect question

Postby atsf sp » Sat Mar 05, 2016 12:16 am

It all depends on the specific signal location and track and what needs to be indicated. To exit our yard we have 3 signals stacked and the top two are always red so the bottom can switch between green, yellow and lunar and of course red since the max signal you can get is a slow clear. This is just one example. Other locations I have seen multiple variations.
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Re: Restricting aspect question

Postby MattW » Sun Apr 24, 2016 5:18 pm

I appreciate the replies. I apologize for not sending my thanks sooner, that's the problem with this forum, it's so far down, it's sometimes forgettable :wink:
But I do have another question, more about the operation than the aspect. When a controlled signal is fleeted, that is setup for a following movement, when can it upgrade to restricting? https://www.youtube.com/watch?v=NKQnLCv32cE For example in this video, after the Amtrak passes and is well into the curve in the distance, the signal upgrades to restricting. Is that a timer or is that based on when the train has cleared the interlocking limits or based on being even further down the tracks?
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Re: Restricting aspect question

Postby atsf sp » Sun Apr 24, 2016 10:07 pm

Its probably because it cleared the plant. But I am not 100%.
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Re: Restricting aspect question

Postby ExCon90 » Mon Apr 25, 2016 4:00 pm

The pop-up beginning at 1:11 seems to cover it; the dispatcher set it up to do that, but had the option of having it remain at Stop. I think the main advantage here is to avoid requiring the following train to stop and wait for a better indication.
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Re: Restricting aspect question

Postby BostonUrbEx » Sat Apr 30, 2016 10:45 am

A fleeted or routed signal will not come in until something better than restricting can be displayed. A restricting has to be specifically called for once a train clears an interlocking and cannot be set up ahead of time.

However, this may be different based on different operating software. This is just based on my own experience.
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Re: Restricting aspect question

Postby Rockingham Racer » Sat Apr 30, 2016 1:36 pm

BostonUrbEx wrote:A fleeted or routed signal will not come in until something better than restricting can be displayed. A restricting has to be specifically called for once a train clears an interlocking and cannot be set up ahead of time.

However, this may be different based on different operating software. This is just based on my own experience.


Check out the video a few posts up. I think it depends on the circuitry at a particular location. In the video, it could've been happenstance that the dispatcher put in a request for a restricting signal, or it could've been called up automatically by the software. It's hard to know unless one is a signal maintainer, and I'm not one of those. :wink:

On older machines that I've seen in towers, the leverman could request a restricting signal by turning its control lever down instead of up. In other instances, because of operational considerations, even turning the lever up would only yield a restricting signal at that location. FA tower in Lawence used to be able to give a restricting signal on the west end of the Lawrence Runner, I think it was. Memory's a little fuzzy; back in the 60's, don't ya know. :-D
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Re: Restricting aspect question

Postby fcqjx » Sun May 01, 2016 10:59 am

BostonUrbEx wrote:A fleeted or routed signal will not come in until something better than restricting can be displayed. A restricting has to be specifically called for once a train clears an interlocking and cannot be set up ahead of time.

However, this may be different based on different operating software. This is just based on my own experience.


I recall going out to watch the passage of a special Amtrak train with experimental ac traction locomotives 450 and 451 towing a German ICE trainset going east on the Amtrak Harrisburg line at Roy interlocking a few miles east of Harrisburg. The eastbound home signals were visible from I was located and, initially, the eastbound track (this was in 1993, before the recent signal update) displayed clear on the position light signal. When the head end pased the signal the signal dropped not to stop but to stop and proceed. After the rear of the train cleared the east of the interlocking limits the signal changed to restricting. So firstly the signal was fleeted, and secondly it was was wired to display the more restrictive stop and proceed while any part of the train was still in the interlocking limits but upgraded to restricting once the entire train was clear of the interlocking but in the block just past the interlocking limit.
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Re: Restricting aspect question

Postby MattW » Sun May 01, 2016 7:12 pm

So I guess really the answer is "it depends" on a lot of things. Very interesting information, much appreciated, keep it coming if anyone has any!
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Re: Restricting aspect question

Postby Train Detainer » Mon May 02, 2016 7:42 pm

fcqjx -
The difference between Stop and Stop and Proceed aspects is the absence (Stop) or presence (Stop and Proceed) of a number plate on the signal mast. It is not possible for a signal to display both - the number plate is either there or it isn't, permanently. Stop signals are used at home signal locations, usually to protect interlockings. Stop and Proceed signals are used for automatic block protection in ABS 251 or 261 territory.

In general -
The function of the signal system is designed by the operating rules people, as the signals have to function in conformance with the operating rules. The operating department works with the signal engineers to ensure the mechanical/electrical/computer operation of the systems meets the needs of the designed operation. All of it must meet the FRA's regulatory requirements and adequate safety considerations, but beyond that it is up to the individual RRs to design their systems, so one RR may use a particular feature or not.

The ability of an interlocking to display a Restricting signal is a matter of its wiring/relay/interlock design or (with computerized interlockings) programming and is specific to the particular interlocking and part of the RR's signal system design. Some RRs might not want a restricting signal for a following signal so the system would be designed like BostonUrbEx described. If you're a commuter RR with no cab signals, passing a signal that required Restricted Speed operation would mean a train would crawl to the next signal, causing delays. If you're a freight RR running long heavy freights in heavily graded territory at lower speeds, the savings in preventing stop/starts would make a case for following on Restricting signals.

The ability of interlockings to display restricting aspects into an occupied block was originally referred to in many places as a Engine Return Signal, as it allowed a Leverman/Operator/Dispatcher to put locomotives back on their trains when dropping or picking up cars without verbal or flag communication. It is also a method of reducing starts/stops as much as possible. IIRC, in a tower with an electric interlocking machine where the handle is turned down to 'force' a restricting, the interlock is overridden and the signal is pinned low so that it cannot upgrade to anything beyond Restricting. It may or may not have maintained a route/switch lock when forced, depending on design, and the rules required crews to ascertain that their route was properly lined in the field. For a Restricting to be displayed with a normal 'handle-up' operation would depend on what type of track was lined to and the operating method in force on that track. Tracks like running tracks or yard tracks would not warrant a better signal indication if the rules required Restricted Speed on them. Except for places where 'forced' Restricting signals are used, there is no dispatcher/operator control over what signal aspects an interlocked/controlled signal displays. They only tell the interlocking the route and 'go' or 'stop'. Stop is the normal condition, and fleeting is only a 'repeat go' command for the interlocking to display the best aspect possible given the track/occupancy/route conditions.
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Re: Restricting aspect question

Postby fcqjx » Sun May 08, 2016 7:09 am

Sorry for the delay; I usually only check inhere on Sundays

Train Detainer wrote:fcqjx -
The difference between Stop and Stop and Proceed aspects is the absence (Stop) or presence (Stop and Proceed) of a number plate on the signal mast. It is not possible for a signal to display both - the number plate is either there or it isn't, permanently. Stop signals are used at home signal locations, usually to protect interlockings. Stop and Proceed signals are used for automatic block protection in ABS 251 or 261 territory.


You are incorrect; I actually witnessed the aspects described on an absolute interlocking (or, perhaps CP) signal lacking a number plate. With position light signals this is possible by only illuminating the neutral light in the bottom unit of the signal which also had lights for the restricting aspect I observed (possibly with additional lights for additional aspects; I don't recall). Obviously your point does apply to color light signals but that was not the case at this location at this time. I don't know if this practice was ever used under the PRR/Penn Central/Conrail era but was used on Amtrak territory where position light signals were still in service.
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Re: Restricting aspect question

Postby ExCon90 » Mon May 09, 2016 4:24 pm

Yes, it was routinely used at North Philadelphia to allow a train to depart immediately following a train that departed from the adjacent track (if both were headed to 30th St., for example); it enabled the train to leave at Restricted Speed, and the cab signal would clear up as soon as the preceding train cleared its block. The B&O also had a Stop and Proceed on a controlled home signal in its rules: two horizontal reds, with a white marker either above or below.
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