[Jovet]

roeter, on 15 November 2012 - 11:17 AM, said:

Just to make it clear : this all applies to North American signalling only. In general, European signalling has no such thing as permissive signals.

Yes, that is definitely true. But European and American signaling philosophies differ for several reasons, one of which being American railroads tend to have a lot more distance between stations/control points.

North America does not have shunting signals, but many American signals do have a "call-on" mode available for use by the dispatcher. This allows a given signal to display a Restricting aspect when it'd otherwise display Stop or Stop and Proceed or whatnot. A train encountering that will not have to stop until required to by Restricted speed. This is helpful here in switching/shunting situations and also when approaching platforms, just like in Europe.

nyc01, on 15 November 2012 - 11:30 AM, said:

It does but with these discussions I've seen in various forums most people don't know the difference between CTC or non-CTC with automatic block signals.

That's why we have to teach them. :sign_thanks: It doesn't help that MSTS has never been able to properly emulate anything other than CTC.

nyc01, on 15 November 2012 - 11:30 AM, said:

In my experience in T&E and as a train dispatcher on three different class one railroads from the mid west, south east and north eastern US I haven’t seen any CTC territory that I've been qualified on where the automatic/intermediate signals return to clear once a train has cleared the block (until of course the dispatcher lines in a following or opposing movement at the last control point).

It does occur, but it's less common. You can see examples of this on http://redoveryellow...s/cs/index.html if you like.

nyc01, on 15 November 2012 - 01:05 PM, said:

Not always, I was qualified on one sub division that still had at least one small segment of ABS 251 (signaled in one direction/current of traffic) in CTC. Again this is rare but it does exist.

Yes, I considered putting an asterisk on that statement, but my post was long enough as it was. I do believe the Horsehoe Curve route would be an example of that, even.

wacampbell, on 15 November 2012 - 02:14 PM, said:

To an non railroader like me, it seems they should have thought up a different color for those 'permissive' signals. With all the focus on safety, this must be a source of error for railroaders - "yes it was red, but I thought it was OK to go. I didn't see the little 'A' on the pole!'".

That "A" is a good but rare example of potential for wrong-side failure. If the A sign is removed or falls off the pole, the signal is automatically upgraded. Not good! Another close to home example of this is Norfolk and Western's colorized position light (PCL) signals, which displayed 2 reds on the main head for Stop and Proceed and added a third red down below for Stop. If that third red burns out... oops!

But I believe that operating across different railroads or divisions with the same signal aspects meaning different things is more of a practical problem (especially under fatigue) than differentiating between absolute or permissive signals.

[Jovet]

nyc01, on 15 November 2012 - 09:06 PM, said:

I looked through probably a dozen of those photos but didn’t see one example of an intermediate clearing up automatically behind a movement. Is there any particular photo I should be looking for?

I noticed it so often I stopped noticing it, to be honest. Looks like most of the instances I noticed were not in CTC territory, like this one.

However, this one is is in CTC territory. The subsequent switch is even lined for the opposing movement that's going to come, even though the train the cameraman is on hasn't cleared the space between CPs.

nyc01, on 15 November 2012 - 09:06 PM, said:

Not to mention that some railroads use an “A” marker (instead of a "D") on distant signals, an example of this is when you are entering CTC from TWC territory. These signals only convey information about the control point ahead and do not convey information about the condition of the block between the distant signal and the control point.

The type of signal you are referring to I always call a Distant signal, with a capital D. To my personal aggravation there are two conflicting definitions of "distant signal" -- one as you described which is NOT a block signal but merely a "warning sentry" analgous to the semaphore with a fishtail blade of yesteryear... and then there's a distant signal which is simply the regular block signal encountered before an absolute (interlocking) signal, such as for an interlocking. That second definition seems to be more prevalent in the eastern US.

[JLChauvin]

roeter, on 15 November 2012 - 11:17 AM, said:

Just to make it clear : this all applies to North American signalling only. In general, European signalling has no such thing as permissive signals. We do have automatic signals but these are just as 'absolute' as any other. Only in case of signal failures can a train receive permission to pass a signal at danger, but that permission must be explicitly given by traffic control, sometimes for each signal, sometimes for all signals up to the first not-automatic signal.
What we do have is signals which allow a train to enter a section allready occupied, e.g. for shunting, multiple trains in a single platform, trains which must be combined (especially MU) etc. But these signals, named shunt or, particular in the UK, calling-on signals, show a different aspect from red. In some countries these are additional to the main signal (subsidiary signals) (UK, Germany (old types)), in others they are integrated and just a special aspect, e.g. flashing yellow (Netherlands).
Finally, an even different type of permissive signal exists (or existed, at least) in the UK. This is (or was) a semaphore signal with a 'ring' at the middle of the arm. This indicated it was a permissive signal, which meant that if it was cleared, it still could be that another train was allready in that section. It was only used on freight lines with low speed. For this signal, "red" means the train has to stop, but "clear" means only that the train is allowed to proceed - not that the line is clear.

Regards,

Rob Roeterdink

French signaling has permissive signals, called "sémaphore" on many routes (one red light). There is even some subtleties, semaphore are always passable on verbal order for a shunting movement, but for others:
- Manual block semaphore absolute (write order to pass "Bulletin S" and in some case "Bulletin MV"), white on black BM board,
- Semi-permissive "Block automatique à permissivité restreinte" semaphore, passable on verbal order, or after a 15 MN delay if impossible to communicate, riding "on sight", white on black PR board,
- Permissive "Block automatique lumineux" semaphore, passable without order, riding "on sight", white on black F Board.

Absolute stop signals are called "Carré" (Square), two red light on main track and a single purple light on other tracks, white on black Nf board. In many case, the signal may show semaphore indication, one red light + a white marker light.
Manual block have a black on white BM board under Nf board,
Semi-permissive have a black on withe PR board under board,
Permissive don't have any board except white on black Nf board.

More in formations here:
http://www.carreweb....isation_en.html

[roeter]

Thanks for the info. I stand corrected.
It goes to show the immense differences between signal systems in various countries - not to mention the complexities this brings to try and cover it all in a single simulation program like OR.
Overall it's pretty strange, though - some countries happily allow their drivers to pass through some signals at danger at their own discretion, in others anything passing a red signal gives powers-that-be nightmares for weeks on end.

Regards,

Rob Roeterdink

[CGW121]

Not only does it differ from country to country, but from railroad to railroad, and from division to division. What with the modern day soup of railroads forming a company I can imagine that it is even more diversified.

[Jovet]

nyc01, on 16 November 2012 - 09:39 AM, said:

All I see with that link is an automatic/intermediate signal displaying stop and proceed.

Better check again... It's showing Approach Diverging.

nyc01, on 16 November 2012 - 09:39 AM, said:

Actually I've noticed that using the term distant signal as reference to the last intermediate signal before a control point has become pretty much railroad slang these days. When I taught operating rules we refrained from using it that way so that it wouldn’t add obvious confusion to the actual definition in the railroads operating rule book.

Well I applaud that approach... signaling is such a detail-orientated subject that there just isn't much room for ambiguity. I avoided the term myself until I decided "Distant" versus "distant" on it. Everything needs to have a specific purpose and meaning. I abhor the term "approach signal" even more. It's like calling an absolute signal a "stop signal" (which is the name of the Stop rule on many railroads!)

JLChauvin, on 17 November 2012 - 12:38 AM, said:

French signaling has permissive signals, called "sémaphore" on many routes (one red light). There is even some subtleties, semaphore are always passable on verbal order for a shunting movement, but for others...

I actually was under the impression that those had or were going to be phased out and go away! But I must be thinking of something else...

roeter, on 17 November 2012 - 06:25 AM, said:

Overall it's pretty strange, though - some countries happily allow their drivers to pass through some signals at danger at their own discretion, in others anything passing a red signal gives powers-that-be nightmares for weeks on end.

Outside of North America, especially the United States, such practice is not that common and is largely frowned upon when it can be avoided. The US only has one type of signal (Color-Position-Light) that only shows Red when a stop is actually required. But such signaling philosophies are prevalent abroad.

CGW121, on 17 November 2012 - 06:44 AM, said:

Not only does it differ from country to country, but from railroad to railroad, and from division to division. What with the modern day soup of railroads forming a company I can imagine that it is even more diversified.

That's what I was talking about above when I said that passing signals showing Red is a small problem compared to the diversity of the same aspects in a single area. Consider the common "Yellow over Yellow" aspect. In the US alone, it can mean Approach Medium (pass next signal not exceeding Medium speed), Advance Approach (prepare to stop for second signal), Approach Slow (pass next signal not exceeding Slow Speed), or Approach Diverging (pass next signal not exceeding speed for diverging movement as listed in timetable). When moving from one railroad or division or territory for another the crews have to be on top of rules changes like these. These examples also don't include special use signals such as switch point indicators or Distant signals or the like.

[Jovet]

roeter, on 15 November 2012 - 02:57 PM, said:

The intention is to show "red" in the F4 track monitor for "absolute stop", and "white" for stop-and-proceed (and other restricted aspects).
So, in F4, a "red" signal will always be an absolute stop.

I think the logic here is a bit fuzzy. There are reasons why permissive signals use Red for stop just like absolute signals do. For one thing, red is universally the most-restrictive color. Second, the majority of railroads can and have required stops at permissive signals prior to proceeding. Such a signal may as well be a "stop and stay" signal until the engineer can actually see with his own eyes that he can safely move beyond the signal. Third, all trains must be prepared to stop at a permissive signal until it can be plainly seen that Restricted speed applies past it. An absolute signal showing a Restricting aspect isn't quite the same since that can often be the best indication possible for a given route/path.

In reality, both types of signals can be passed when red ("at danger") in difference circumstances, so 'absolute stops' are a bit of a myth. A while back I was going to propose a few different methods for indicating signal states on Open Rails's Track Monitor. Never got around to talking about it until now, though. One thing I really wished MSTS could do is to allow a signal to be upgraded progmatically when permission to pass it is obtained (i.e. a call-on).