[roeter]

Not sure if this is the right place for this question, but it has to do with signalling so it seems the most proper place.

On some US routes, I have come across locations where signals are placed at very short distance from each other. The question is what aspect approach signals should show in this situation.

Here is an example for Whitefish route.

 Whitefish_1.jpg (800.45K)
Number of downloads: 12

Speed in this area is 40 mph. As can be seen, signal A is just a short distance from signal B. If signal A is at danger, signal B will show approach.
But what aspect is shown on the signal before B? According to the chards, this should be clear or, if 4 light aspect is available, advance approach. But if signal B is approached at the speed which is normally maintained after passing a signal at clear or advanced approach, clearly the train will not be able to stop at signal A.
Are there special rules for situations like this (of which there are quite a few on the Whitefish route, and on other routes as well).

These situations also occur on European routes but I do know that these are indeed handled in special ways in various European systems. But I have not come across any information how this is handled in US systems.

Or, indeed, is this placement not realistic and are these to be considered as errors in the route creation?

Regards,
Rob Roeterdink

[jeanmarc]

A restricting indication, flashing red or lunar light. Travis Ebner is a master in US signalling.

Thank for your work Rob.

[Jovet]

roeter, on 21 November 2023 - 03:33 AM, said:

Speed in this area is 40 mph. As can be seen, signal A is just a short distance from signal B. If signal A is at danger, signal B will show approach.
But what aspect is shown on the signal before B? According to the chards, this should be clear or, if 4 light aspect is available, advance approach. But if signal B is approached at the speed which is normally maintained after passing a signal at clear or advanced approach, clearly the train will not be able to stop at signal A.
Are there special rules for situations like this (of which there are quite a few on the Whitefish route, and on other routes as well).

Put simply: there is not a consistent answer in this situation. It really depends on the needs of the railroad in each specific situation, and what the signaling designer/engineer believed best at the time.

The chosen solution depends on:

• The maximum speed of the line involved
• The maximum weight and associated stopping distance of the heaviest train expected to use the line
• The design of the signaling schema (e.g. 3-aspect or 4-aspect, etc.)
• The customary or expected routing of trains through the area
• Preferred positioning of (stopped) trains, such as for stations, level crossings, etc.
• Experience and expectations of train crews (e.g. prior existing similar situations, etc.)

In this situation, I do not see this situation as likely: [A] Stop ← [B] Approach ← [C] Clear

More likely would be: [A] Stop ← [B] Approach ← [C] Approach MediumApproach Medium being the "fourth" signal aspect of the regular sequence, even if it's not in regular use on the line (e.g. most signal blocks are 3-aspect).
Double Approach could be implemented: [A] Stop ← [B] Approach ← [C] Approach
Or, as mentioned, possibly a Restricting: [A] Stop ← [B] Restricting ← [C] Approach

[roeter]

Thanks for the replies. So my suspicion was justified, the way this has been set up in the route is wrong. Another route to add to the list of those that need resignalling ....

Regards,
Rob Roeterdink

[Jovet]

roeter, on 22 November 2023 - 12:52 AM, said:

Thanks for the replies. So my suspicion was justified, the way this has been set up in the route is wrong. Another route to add to the list of those that need resignalling ....

Any route that uses default USA2 or really any default signaling can be safely considered in need of re-signaling.

[ebnertra000]

I think Jovet's hit it about on the head. I would be more likely to use either the Double-Approach or Restricting methods with a distance that short, unless normal operating speeds are very slow there.

That said, Signal A looks to be in some kind of yard, which makes me question whether a signal should even be there. Without any further context, I would advocate for the removal of signal A, with entry to the yard being governed by Signal B showing a Restricting signal.

I am also very much on board with Jovet's suggestion that any route using US2 signals is probably best re-signalled