• Exit signals at interlockings?

  • General discussion about railroad operations, related facilities, maps, and other resources.
General discussion about railroad operations, related facilities, maps, and other resources.

Moderator: Robert Paniagua

  by MattW
I've been intensely studying various signal systems for the past few months. I've learned a lot here and elsewhere, but I ran across something the other day that I hadn't seen at least here in the U.S. On The Position Light Blog, http://position-light.blogspot.com/2014 ... -safe.html" onclick="window.open(this.href);return false; in that post, the first image, I see dwarf signals that look like they face toward the crossover. Are these exit signals? If they are, are they to give a signal aspect for a train exiting the interlocking from a diverging movement? If not, then what are they for? The exit signals do make sense to me, as I recall, there are some signal rules that require approaching the next absolute signal prepared to stop, and in theory, it would make sense to provide an aspect to go ahead and let the train upgrade its speed rather than crawl along prepared to stop at the next signal. If not, then I have no clue.
  by Jersey_Mike
That signal is facing away from the crossover. It is being replaced by the new mast style CPL on the far left. You just can't see the lamps because the photo is under exposed. I suggest that when you have similar questions you first try the comment feature on the blog :wink:
  by MattW
Thanks for the info! I'm sorry, I had meant for the question to be a bit more generic than it came out, with your excellent post only being used to illustrate. So I'd like to ask more broadly to anyone that knows, are "exit" signals used at any interlocking?
  by ExCon90
One example I know of (obsolete -- they're all gone now) was on the Pennsylvania in manual block territory. The usual practice was to have a controlled home signal (square blade) at the entrance to the interlocking, displaying (as needed) Clear, Approach, Medium Clear, Restricting, and Stop. At the exit from the interlocking, directly across from the opposing entering home signal, was a block signal (round-end blade) displaying Clear Block, Permissive, and Stop. The Long Island had similar arrangements in places (in position lights), but I think they're all gone too.
  by ExCon90
Just remembered another one I see all the time. A southbound SEPTA airport train leaving PHIL interlocking encounters a position-light signal (governing Tracks 4 and 5 only) protecting where the airport line diverges from Track 4 and Track 5 trails into it. Immediately beyond the Track 4-5 merge is a color-light signal governing the single-track airport line. The best I've ever seen on that signal is Approach Medium. I suppose the reason for the signal immediately beyond PHIL is that PHIL is controlled by Amtrak and the airport line track beyond that by SEPTA -- either that or because there's no position-light aspect for Medium Approach Medium, so the best you could get would be Medium Approach if the next signal on the airport line is Medium Clear.
  by amtrakhogger
There are still a few exit signals out there. One is 3 track at Dock going west and there are two at Charles Interlocking (B&P Jct) going south on 2 and 3 tracks.
  by lstone19
A number of exit signals along my daily commute on the Metra Milwaukee West line. A-5 has exit signals both directions as does B-12. Although A-5 is currently in the midst of what appears to be a total replacement of all signals, interlocking, and special track (switches and the movable point frog crossing on the West/North split (West track 1 crossing North track 2) so who knows what it will be like when done.
  by krispy
LIRR still has them, they're block signals governing that block. You also have interlocking signals which govern a route within an interlocking, and sometimes in simple interlockings you could combine the two. They would indicate the condition of the block in Manual Block territory (not necessary if there were wayside signals), or provide an absolute block for speed failure equipment or unequipped trains (or TC's) for automatic blocks with NO wayside signals.

This may change with PTC, we'll see...