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Cab signal vs. wayside signals
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   Author  Topic: Cab signal vs. wayside signals  (Read 621 times)
thatlumox
TRAINing
Posts: 21
Cab signal vs. wayside signals
 
« on: Feb 27th, 2007, 8:49pm »
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Is there any reason why modern railroads would still use wayside signals instead of a cab signal system? It seems the safety aspect of cab signal and Automatic Train Control would make wayside signals almost obsolete.

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George_Harris
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Posts: 3845
Re: Cab signal vs. wayside signals
 
« Reply #1 on: Feb 28th, 2007, 4:43am »
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Expense.  Not just installion expense, but maintenance expense.
 
If you have cab signals only, every engine operated on the line must be equipped with it.  Since the American railroad system is less than 1/2 equipped with signals of any kind, and most of the time trains have either two or three engines on the front, that means equipping a lot of engines with signal equipment that must be maintained in a fail-safe condition that is used on a small fraction of the time the engine is in use.  
 
You still have to have the circuits in the track to provide the current to activate the cab signals.  Signal systems are required to have a level of reliability far beyond anything else in the railroad world and almost everything else in the world in general.
 
Even if you have only ATS you still have to have special equpment on every engine, or at least the lead engine on every train that operates on the line.  
 
Use of cab signals and ATC/ATS equipment actually made more sense in steam days when engines were usally limited specific assigned territories and normally operated with only one per train.
 
If cab signals and ATC guranteed absolute safety, there would be no accidents at all on the northeast corridor or such lines as the ex C&NW between Chicago and Omaha, and that is simply not so.  There has been no safety system created by man that is completely immune to mistakes and stupidity.  
 
Some railroad lines are going virtually wrong way (in my opinion) on CTC and no longer equipping lines throughout.  The apply CTC "islands" at some of the sidings so they can power the switches but not have to apply circuitry and signals to the entire line.
 
George


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RailCop
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Posts: 299
Re: Cab signal vs. wayside signals
 
« Reply #2 on: Mar 2nd, 2007, 2:43am »
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George, I think only the lead unit needs to be equipped with cab signals. Trailing units do not require cab signals.  Can anyone verify this for us?
 
KT


« Last Edit: Mar 2nd, 2007, 2:44am by RailCop » Logged

Let's 'B-Safe' out there,
Kevin
George_Harris
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Posts: 3845
Re: Cab signal vs. wayside signals
 
« Reply #3 on: Mar 2nd, 2007, 3:44am »
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on Mar 2nd, 2007, 2:43am, RailCop wrote:       (Click here for original message)
George, I think only the lead unit needs to be equipped with cab signals. Trailing units do not require cab signals.

This is true.  However, Murphy rules everything.  If you only have say one unit out of four, or any other proportion less than 100% equipped with cab signals, they you are going to constantly be running into the need to run a train without having an appropriately equipped unit at hand or having it on the wrong end of the set of engines.
 
For years, and maybe still, for all I know.  For this reason properly equipped C&NW units had to lead between Chicago and Omaha / Fremont for all freights run through with UP because UP engines were not equipped for the the C&NW ATC system.  These units were added / taken off at Fremont or Omaha.
 
George


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CHESSIEMIKE
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Re: Cab signal vs. wayside signals
 
« Reply #4 on: Mar 2nd, 2007, 5:38pm »
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on Mar 2nd, 2007, 3:44am, George_Harris wrote:       (Click here for original message)

This is true.  However, Murphy rules everything.  If you only have say one unit out of four, or any other proportion less than 100% equipped with cab signals, they you are going to constantly be running into the need to run a train without having an appropriately equipped unit at hand or having it on the wrong end of the set of engines.
 
For years, and maybe still, for all I know.  For this reason properly equipped C&NW units had to lead between Chicago and Omaha / Fremont for all freights run through with UP because UP engines were not equipped for the the C&NW ATC system.  These units were added / taken off at Fremont or Omaha.
 
George
CSX ran into this when they took over the RF&P.  They wanted to get rid of the older RF&P power, but had to get the cab signal equipment out of the old units first.
CHESSIEMIKE


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Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.
Norm_Anderson
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Posts: 1728
Re: Cab signal vs. wayside signals
 
« Reply #5 on: Mar 3rd, 2007, 2:22pm »
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On a related note, what kind of successes (or lack of same) are railroads experiencing with GPS and proximity-detecting systems?  Would such things be just as cost-prohibitive as ATS?  Might such a system ever be made cheaply and reliably enough to do away with most conventional signalling altogether?
 
 
Regards,
 
Norm


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ed2903
TRAINing
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Re: Cab signal vs. wayside signals
 
« Reply #6 on: Apr 10th, 2007, 10:03pm »
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One of the reasons for leaving both systems is in event of a trains cab signal problem or failure, the wayside signals will govern the train.  Also if MoW or someone else is in a highrail vehicle the wayside signals will govern  there movements.

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George_Harris
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Re: Cab signal vs. wayside signals
 
« Reply #7 on: Apr 10th, 2007, 11:32pm »
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Generally even if you have full ATC and cab signals you will still leave the wayside home signals at interlockings.  What this means is that in case of cab signal failure, you generally move between signal points under manual block rules and you must approach the locations of the home signals prepared to stop.

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prostock19
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Posts: 486
Re: Cab signal vs. wayside signals
 
« Reply #8 on: Jun 3rd, 2007, 5:11pm »
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I am qualified on some territories that are cab signal equipped.  Most of the trains coming into the territory have a cab signal equipped leader, but when they don't they have to tack on an add-on unit with cab signals...sometimes a GP-40 local engine.
 
Most of the trains though are equipped with 2 cab signalled units on either end so that they can go both ways if needed.  Rules are that you cannot leave a terminal without working cab signals with the exception of a work train.


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Les_Shepherd
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Posts: 425
Re: Cab signal vs. wayside signals
 
« Reply #9 on: Jul 8th, 2007, 2:42am »
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Because of my limited knowledge of the subject I am reluctant to enter conversation on signalling matters but there is an instance of failure of BOTH visual and audible warning systems. This is the Southall disaster in London on 19 Sept 1997.
 
The culprit was an Intercity125 operated by First Great Western. These have "loco" units at each end and operate up to 125mph. The line and the units are fitted with an 'Audible Warning System' (AWS) in the cabs and activated from track mounted transponders. When the train departed Swansea that morning the AWS at the London end was not working and had been isolated. It had not been working for some days and through a variety of maintenance failures had not been repaired.  
At Southall the signalman had decided to cross a freight in front of the approaching IC125, he had plenty of time to do so and the signals were set accordingly. The first of 2 caution signals was 1.6 miles away giving first warning to the express. The express was travelling at 125mph as it approached the station at Hayes & Harlington and facing green signals; the first caution was 1200 yards ahead and obscured by the station buildings. The driver acknowledged his control and left his seat to pack his bag for a quick departure on arrival at Paddington. In this time (measured as 16.3 seconds) the train passed both caution signals wthout him seeing them and with no audible warning. By the time he  returned to his seat he was facing a red signal 3/4 of a mile ahead and insufficient room to stop. One carriage on the train was bent into a V shape.
 
As prostock19 says, trains should not be permitted to depart unless the audible controls are working. The event above reflects slackness in UK procedures at the time.


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ClydeDET
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Re: Cab signal vs. wayside signals
 
« Reply #10 on: Dec 22nd, 2007, 10:30pm »
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Only certain cure for stupidity or carelessness is - death. And even so, it only means THAT person won't do it again.
 
Recently got a Tomtom GPS based navigation system for the car. It would sure enough keep you advised of where you are and I see no reason it couldn't be set up to transmit to dispatch (apparently the trucking industry does this now). Location is typically within (at worst) 10 meters, sometimes within .3 meters. Oh - it cost $139.99 + tax. There is an add-on that keeps track of construction and even traffic jams. The little boxes seem quite reliable. And they tell you ow fast you are going and have a girl inside who will tell you it is time to turn, and which direction...
 
This suggests to me that for maybe $500   you could have a system that would tell the engineer where he was, tell the dispatcher where the locomotive is, and probably make it aware of any other train within some established distance. Whether you'd want to have nothing else, i ain't sure, but should be a helpful thing.
 
I really would like to know how the get a girl in that little box.


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brokenrail
Chaser
Posts: 76
Re: Cab signal vs. wayside signals
 
« Reply #11 on: Dec 23rd, 2007, 10:46am »
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on Apr 10th, 2007, 10:03pm, ed2903 wrote:       (Click here for original message)
One of the reasons for leaving both systems is in event of a trains cab signal problem or failure, the wayside signals will govern the train.  Also if MoW or someone else is in a highrail vehicle the wayside signals will govern  there movements.

 
 
Track equipment does not use signals.  Most track machinery is insulated between the rails to avoid the temptation of using the the track shunting ability of the equipment.  Even a single locomotive or self propelled car may not shunt the rails reliably.  MoW must use another form of authority to use a main track.


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k5sss
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Re: Cab signal vs. wayside signals
 
« Reply #12 on: Dec 23rd, 2007, 9:32pm »
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on Dec 22nd, 2007, 10:30pm, ClydeDET wrote:       (Click here for original message)
Recently got a Tomtom GPS based navigation system for the car. It would sure enough keep you advised of where you are and I see no reason it couldn't be set up to transmit to dispatch (apparently the trucking industry does this now). Location is typically within (at worst) 10 meters, sometimes within .3 meters. Oh - it cost $139.99 + tax. There is an add-on that keeps track of construction and even traffic jams. The little boxes seem quite reliable. And they tell you ow fast you are going and have a girl inside who will tell you it is time to turn, and which direction...
 
This suggests to me that for maybe $500   you could have a system that would tell the engineer where he was, tell the dispatcher where the locomotive is, and probably make it aware of any other train within some established distance. Whether you'd want to have nothing else, i ain't sure, but should be a helpful thing.

"Quite reliable" isn't good enough for the FRA.  For comparison, aviation GPS systems cost $10-15k because of all the FAA's extra reliability requirements (most importantly, recognizing when they've failed).  The Class I RRs alone have about 21k locomotives, so that's ~$300M just for the pretty displays.  Now you have to link them to the radios to transmit position to the dispatcher, receive movement authority information, and enforce speed limits (fixed and temporary) via a link to engine controls.  Don't forget all the equipment in the dispatching office too.  And you have to maintain all of it, keep maps updated, etc.  You're talking billions for the industry.  Further, 10m resolution isn't good enough for multiple-track lines, where track centers can be as little as 13ft (4m) apart, nor does GPS work in tunnels.
 
Also, as much as I love my TomTom, it frequently sends me onto roads that don't exist (anymore) or are one-way in the wrong direction, tells me to take freeway exits that have been closed or moved, "finds" me on parallel roads, etc.  There is a map correction function, but it takes a lot of work and doesn't seem to take effect until their folks have reviewed and approved a change; I've been waiting months for them to remove some closed roads near me...  Also, I have the traffic receiver, and while it occasionally works, I've spent a lot of time sitting still when there was no advisory for the road I'm on -- and when I turn off to go around the jam, it constantly tries to redirect me back into the mess.
 
In short, don't look at what is "good enough" for consumer use and think that it's remotely applicable to a safety-critical industrial system.  While one can scale industrial systems down to consumer use, going in the other direction is virtually impossible.


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ClydeDET
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Re: Cab signal vs. wayside signals
 
« Reply #13 on: Dec 28th, 2007, 3:05pm »
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All aviation gear costs c.10 times what any other application would. Not because it is really better (more reliable, more fail-safe,. etc) but because it is AVIATION related.  
 
And yes - i know that what is good enough for consumers isn't always good enough for commercial use. But - while 10 meters may not be good enough, that's about the worst my unit is ever guilty of. More typical is 1 down to 3/10ths of a meter. I remain of the opinion that a dedicated railroad set could be developed for an issue cost of around $500-1000 and you wouldn't ahve to have one for every loco - they could be built portable and part of the crew gear, like lanterns. Yeah - a different way to do things and probably NOT the ONLY thing you'd care to rely on, but  worth thinking about.
 
Oh - raiul lones don't change as often as roads for cars do... zand I still want to know how they get that girl into that little box.


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MP 247
Railfan
Posts: 110
Re: Cab signal vs. wayside signals
 
« Reply #14 on: Jan 2nd, 2008, 8:15pm »
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I think the GPS thought is an interesting one, though there are some things so still think about.  
 
Though Garmon/TomTom units can give accuracy of a few feet (which is questionable) you have to move to a WAAS based system to get a guaranteed minimum 7.8 m and a usual working range of around 1 m.  WAAS systems are more expensive (guessing in the $1000 range) and to go even to a greater degree of accuracy, even more money is needed (to go to a subscription signal correction or a set up base stations).
 
GPS can lose signal in a lot more places than tunnels - along tree lines and close to hills - pretty much anywhere you lose a southern exposure.  In car based systems if you lose signal the GPS figures in what direction you were going and at what speed and does the math.  I'm not sure if that would be an acceptable system of trains - it would me most likely that base stations would  need to be set up.
 
Communicating back to a central station requires more electronics and money.  In truck tracking / Onstar you need a cell phone signal (around $30/mo) to call back and tell people where you are.  Over a locomotive fleet that could add up.
 
I'm not discounting the GPS idea.  I think it a has a lot of potential long term.  However it is a lot more complicated than first guess.
 


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