Speed signalling

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Speed signalling 17/12/2014 at 23:27 #66775
Finger
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BTW, could SimSig handle areas with speed signalling?
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Speed signalling 18/12/2014 at 00:19 #66777
maxand
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Please try to stay on-topic. This deserves its own thread.
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Speed signalling 18/12/2014 at 02:02 #66779
GeoffM
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" said:
BTW, could SimSig handle areas with speed signalling?
Yes, to a certain degree. It could handle a handful of different speeds but not a wide range. Again, to a certain degree, US and (US-style) Australian signalling.

SimSig Boss
Last edited: 18/12/2014 at 12:20 by Peter Bennet
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Speed signalling 18/12/2014 at 11:42 #66782
maxand
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As a non-professional, I for one, having made an effort to learn the Route Signalling system used in the UK in order to play SimSig, find Speed Signalling confusing, even though a variant of it is used in my home state of Victoria in Australia. So some explanation seems in order.


Quote:
Route signalling and speed signalling

Signalling of British origin generally conforms to the principle of route signalling. Most railway systems around the world, however, use what is known as speed signalling.

Under route signalling, a driver is informed which route the train will take beyond each signal (unless only one route is possible). This is achieved by a route indicator attached to the signal. The driver uses his route knowledge, reinforced by speed restriction signs fixed at the lineside, to drive the train at the correct speed for the route to be taken. This method has the disadvantage that the driver may be unfamiliar with a route onto which he has been diverted due to some emergency condition. Several accidents have been caused by this alone.[3] For this reason, in the UK drivers are only allowed to drive on routes that they have been trained on and must regularly travel over the lesser used diversionary routes to keep their route knowledge up to date.

Under speed signalling, the signal aspect informs the driver at what speed he may proceed, but not necessarily the route the train will take. Speed signalling requires a far greater range of signal aspects than route signalling, but less dependence is placed on drivers' route knowledge. (Wikipedia - Route signalling and speed signalling)
If it were as simple as that, it would not be too difficult to add an extra set of icons when simulating American or Australian layouts. However:

Quote:
There are two main types of signaling aspect systems found in North America, Speed Signaling and Weak Route Signaling.[2] Speed signaling transmits information regarding how fast the train must be going in the upcoming segment of track, weak route signaling transmits information related to the route a train will be taking through a junction and it is incumbent upon the engineer to govern the train's speed accordingly. Weak Route Signaling is applied with the term "Weak" because some speed signal aspects may be used in the system and also because exact route information is not typically conveyed, only the fact of a diverging or straight route, each having a predictable range of known speeds.

Typically railroads in the Eastern United States ran speed signaling, while railroads in the west used route signaling, with some mixing of systems in the Midwest and South. This was due to the lower train density in the west combined with generally simpler track layouts. Over time, the route signaling railroads have incorporated segments of speed signaling through merger and have also adopted more speed based aspects into their systems. Of the five major Class 1 railroads in the United States, CSX uses speed signaling, Union Pacific and BNSF use speed enhanced route signaling and Norfolk Southern uses a mix of speed and route signaling based on the original owner of the line. Commuter railroads and Amtrak all use speed signaling where they own or maintain the tracks they run on. Canadian railroads all use a strong system of speed signaling in Canada, but have some segments of route signaling on lines they have acquired in the United States. (Wikipedia - North American railroad signals)
Here are two other useful links on US conditions:
Railway Technical Web Pages
Primer On American Railroad Signals

In Australia it varies from state to state. Again, Wikipedia describes this very well. For example, in my home state:

Quote:
The railways of Victoria use a mix of railway signalling practices: British route signalling with home and distant signals (2 position signalling) and American speed signalling (3 position signalling)... (Wikipedia - Australian railway signalling)
John Hinson, known for his website The Signal Box, wrote an amusing account of Melbourne speed signalling as seen through UK eyes, titled Speed Signalling on the suburban lines of Melbourne

After reading these articles it becomes clear to me that to simulate North American and Australian routes accurately would require an immense amount of preparatory coding by SimSig's developers, almost a complete rewrite of the core code, which would execute slower and be harder to debug. Since there are many more signalling icons required, implementing this might require much higher screen resolution and completely new graphics, whereas the present system using simple icons faithfully reproduces the real life simple VDU display as used all over the UK.

I think it would also make writing timetables more difficult because in speed signalling the onus is now on the driver to adhere to the new speeds.

If and when the UK finally adopts speed signalling or changes to moving-block technology it will be time to consider upgrading SimSig. In the meantime I think most of us have our hands full just coping with what we have.

Last edited: 18/12/2014 at 11:46 by maxand
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Speed signalling 18/12/2014 at 13:59 #66789
Muzer
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I've always wondered - presumably in speed signalling, the signallers have to be even more careful of a wrong route, as it's much more likely for a driver to accept a wrong route. What additional mitigation, if any, against wrong routes do they have?
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Speed signalling 18/12/2014 at 19:37 #66803
GeoffM
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" said:
I've always wondered - presumably in speed signalling, the signallers have to be even more careful of a wrong route, as it's much more likely for a driver to accept a wrong route. What additional mitigation, if any, against wrong routes do they have?
Talking of US signalling, drivers would have some idea of a wrong route if there were only 2-3 possible choices. This is because a "straight" route would get one aspect, let's say green over red, while a diverging route would get a different aspect, let's say red over green. Some have two diverging speeds, medium and slow (?), which again would be a different aspect.

SimSig Boss
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Speed signalling 18/12/2014 at 20:04 #66805
metcontrol
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Thank you for the explanation of what is being discussed here.
For a time there I thought perhaps this was a discussion regarding certain areas already available being enabled for super-quick mouse clicks or similar, for those with nimble enough reflexes to set routes with the sim running on the fastest setting. :doh

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Speed signalling 18/12/2014 at 20:05 #66806
Finger
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" said:
" said:
BTW, could SimSig handle areas with speed signalling?
Yes, to a certain degree. It could handle a handful of different speeds but not a wide range. Again, to a certain degree, US and (US-style) Australian signalling.

So, no German or East European (OSShD*) signalling is possible?

The biggest problem with speed signaling is that you don't set speed profile according to the track, but, depending on the circumstances, you might get quite different aspects leading to the same track, resulting in different permissible speeds. It can mean you'll get a 40 kmh restriction even for straight route, which is lifted once route forward (or second route forward, or third...) is set.

" said:
I've always wondered - presumably in speed signalling, the signallers have to be even more careful of a wrong route
Basically, you've said it. It isn't much of a problem, because the driver will stop anyway when routed somewhere he's not supposed to go. It can be pernicious, however, when the signaler accidentally sets route to a shorter track than normally expected by drivers. There have even been accidents on this account, under quite intriguing circumstances.

*) personally I think it should be written OSZhD, but nevermind

Last edited: 18/12/2014 at 20:16 by Finger
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Speed signalling 18/12/2014 at 20:06 #66807
Finger
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220 posts
" said:
Thank you for the explanation of what is being discussed here.
For a time there I thought perhaps this was a discussion regarding certain areas already available being enabled for super-quick mouse clicks or similar, for those with nimble enough reflexes to set routes with the sim running on the fastest setting. :doh

Thanks! That made my day

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Speed signalling 18/12/2014 at 20:26 #66810
GeoffM
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" said:
So, no German or East European (OSShD*) signalling is possible?
As I said, to a certain degree.

SimSig Boss
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Speed signalling 19/12/2014 at 20:45 #66848
Forest Pines
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I suspect you could probably simulate the West German signalling system, which is still widely used, by using the defensive driving rules, as the West German system only really has "line speed" or "restricted" speeds. The East German system is much more complex, and the modern German "combined aspect" system is in many ways the British four aspects with arbitrary speed indications on top!

Incidentally I've read that in Germany theatre indicators showing letters are used at major junctions to refuce the risk of a driver taking a wrong route..

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Speed signalling 19/12/2014 at 21:43 #66852
Jan
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" said:
I suspect you could probably simulate the West German signalling system, which is still widely used, by using the defensive driving rules, as the West German system only really has "line speed" or "restricted" speeds.
I wouldn't say so. Yes, there is a dedicated aspect for restricted speed (40 km/h), but with the help of theatre indicators any other speed (as long as it's a multiple of ten) can be shown as well. In that regard it is actually even more flexible than the OSShD derived signalling systems, including the East German variety, which can only show a certain number of fixed speed steps and don't use any theatre indicators at all.

Additionally, in Germany you have a distinction between the station area and the plain line, which is important when having to decide how long a speed limit is valid, and there is a slightly weird rule about what happens within a station when an intermediate/exit signal is showing a higher speed limit than the entrance signal - basically after a scheduled stop at the ordinary stopping position the train can accelerate immediately, while in all other cases the complete train needs to pass the signal before the driver is allowed to accelerate.

And that's just covering the signalling-driver interface, if you actually want to simulate a signal box you'll find lots of other differences as well...

Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick.
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Speed signalling 19/12/2014 at 22:38 #66854
Forest Pines
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" said:
" said:
I suspect you could probably simulate the West German signalling system, which is still widely used, by using the defensive driving rules, as the West German system only really has "line speed" or "restricted" speeds.
I wouldn't say so. Yes, there is a dedicated aspect for restricted speed (40 km/h), but with the help of theatre indicators any other speed (as long as it's a multiple of ten) can be shown as well. In that regard it is actually even more flexible than the OSShD derived signalling systems, including the East German variety, which can only show a certain number of fixed speed steps and don't use any theatre indicators at all.
The West German signalling system - the "Hp" system, which distinguished stop signals and distant signals by head shape - didn't include theatre indicators as far as I'm aware. You're thinking of the post-reunification "Ks" signalling system which I also mentioned in my post - it has four aspects that are very similar in meaning to British signalling, but with additional white and yellow theatre indicators to display maximum speeds at the current or next signal.

You're right about the problems that would be involved in simulating the "points zone" - I'm not sure if that could be done in SimSig at present.

Last edited: 19/12/2014 at 22:39 by Forest Pines
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Speed signalling 20/12/2014 at 11:58 #66858
Jan
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" said:
The West German signalling system - the "Hp" system, which distinguished stop signals and distant signals by head shape - didn't include theatre indicators as far as I'm aware.
Well now you can say that you are aware ;)

Here with fixed indicators (in combination with mechanical signalling sometimes even a moveable variety is used):


... and with theatre indicators. For speeds up to 60 km/h, the "proceed slowly" aspect (Hp2 and Vr2) is used, for speeds above that the normal "proceed" (Hp1 and Vr1) aspect is shown. In this case, we have a distant signal repeater (the German equivalent of a banner repeater) as indicated by the additional white light and the missing distant signal plate, therefore the advanced speed warning - displayed with yellow digits - gets repeated as well.


This signal is also exhibiting the Zs2 direction indicator you mentioned, in this case it is displaying 'R' for - I think - Rheintalbahn.


Alternatively, as long as all sets of points allow higher speeds than the standard 40 km/h, it is possible to simply redefine the meaning of the "proceed slowly" aspect at all entrance/intermediate/exit and/or block signals of a certain location and direction to 50 or 60 km/h via the working timetable.

Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick.
Last edited: 20/12/2014 at 12:00 by Jan
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The following user said thank you: Forest Pines