Placing of Signals on a model layout...

[Anonymous]

I'm planning my first permanent model railway layout to build in a spare room I have designated.

I am having a little trouble with the positioning of signals, regardless of the position I begin to place the signals I am unsure what signals to use. Since you have a selection of three distance signals and three semaphore signals to chose from.

The first being one that can show VR-0/VR-1 (Stop/Proceed) the second being VR-0/VR-2 (Stop/Proceed Slowly) and the third being VR-0/VR-1/VR-2 (Stop/Proceed/Proceed Slowly).

The question I have is how you would know which one to place where on the layout, how is it calculated that the stop and proceed signal should be placed in a certain area, and a stop and proceed slowly signal should go somewhere else.

Can someone please help to give some understanding of this…

[nbrodar]

In North American signalling
For block occupancy...
Clear (proceed) - the next two blocks are clear.
Approach (proceed slowly) - the next block is clear and be ready to stop at next signal.
Stop - stop the next block is occupied.

For turnouts
Clear - switch lined normal movement
Approach - switch lined diverging movement (from point end)
Stop - switch lined against movement (from frog end)

Signals are best placed around turnouts, as they are natural break points for blocking. And most model railroads are not large enough to support true home/distant signalling.

I place my signals at the turnouts. One head to show the condition of the next block and one head to show turnout postion.

Nick Brodar

[Anonymous]

And even dummy signals are a good way to indicate where a train should stop before a turnout so that it wouldn't interfere with a train on the other track. I haven't decided if I'm going to use live signals yet, but either way I use dummies in places where the observer can't really see if it's lit or not.

[nobullchitbids]

Well, the answer is a little more complicated than what we've seen so far. The inquirer uses terminology which suggests he might be British, and that makes the answer even more complex.

Essentially, there are two methods for signaling: Route signaling and speed signaling. The former is used in Great Britain; the latter in North America. Thus, an English interlocking mast might use three heads where an American mast would use only two, reserving the third head for an additional indication, the "call on."

Let's start with placement: First thing to do is identify all of the railroad's interlocking plants. These are areas where switches bring routes together but not necessarily provide access to lineside industries.

Whatever system one uses, interlocking plants must be protected with absolute stops -- to prevent "cornfield" meets. Those stops must be time-delayed to prevent a train from receiving a stop signal too late to actually stop. In North America, interlocking signals have the heads stacked atop one another, so that the signal's aspects would appear in a vertical row. Using a three-headed signal for reference, the aspects would be:

Red over red over red: Absolute stop;
Green over red over red: High-speed clear;
Yellow over red over red: High-speed approach;
Red over green over red: Medium-speed clear;
Red over yellow over red: Medium-speed approach;
Red over red over green: Low-speed (switching) approach;
Red over red over yellow: Call on (be prepared to stop at any sign of any obstruction).

Also, many railroads today use four-block signaling, incorporating e.g. flashing yellow, which indicates that the next signal is yellow, not red, and that trains over a certain weight must slow down sooner.

Open country is protected by block signals, not interlocking signals, and for these there is only the single head:

Red (stop);
Flashing red (permissive stop/call on)
Yellow (approach);
Flashing yellow (reduce speed);
Green (clear).

When two heads appear on a block signal, they are not aligned vertically and therefore operate independently of each other, for separate tracks; where absolute stop is required on red, the block signal will be designated thus with a number plate or, more likely, a square plate bearing an "A" (older installations).

On single-track lines, today, the portion of single track between passing sidings often is directionally signaled -- it is possible to clear only one direction at a time, even if the intervening signals be only block signals. Thus, one never would see back-to-back greens.

Of course, one of the problems often confronting the model railroad is that there is rarely much space between interlocking plants; hence, the number of block signals required actually is quite small, and a large number of the interlocking signals remain permanently red. As for modeling working interlocking signals, the one way I found to be successful is to use the old Twin-T circuit wired in a way that allows contacts on a turnout's switch machine to short the display units (DUs) when the turnout is misaligned, then monitor it all with a polarity ground to regulate direction of travel.

Needless to say, a full discussion of this is beyond the posting capabilities of this forum and would require a full magazine article or two.