Details Table of Contents
Scenery, Structures & Details Table of Contents
Scenery Table of Contents
- 1 Overview
- 2 Speeds
- 3 Aspects, Rules, and Indications
The NEB&W has taken its ideas from both the Rutland and D&H railroads throughout its existence. Signaling should be no different. However, the Rutland was unsignaled, so we are left with the D&H signaling system and style for our railroad.
The D&H used CTC (Centralized Traffic Control) to control train movements. The main CTC panel was located in the D&H building in Albany, NY. There were also local CTC panels at some major interlockings.
CTC relies on a remote operator to keep track of train movements. This operator (otherwise known as a dispatcher) can then line switches to set up meets, or arrange for trains to travel out on a branch line. This is how we plan to use CTC on the NEB&W. The panels were the standard Union Switch & Signal style.
For an example of CTC signaling, visit Logic Rail Technologies CTC demo.
Finally, the D&H used a Searchlight style of signal, most likely also a standard Union Switch & Signal signal head. The APB/ABS signals (automatic) were single-headed, the distant signals were double-headed, and the interlocking signals were triple-headed. This gives the opportunity for 27 different combinations! However, not all of them were used.
ABS (Automatic Block Signaling) was most commonly used in double-track areas. The system automatically reads two blocks ahead and displays the appropriate aspect. This can lead to collisions in single-track areas if the trains pass a signal at nearly the same time. (Jeff Otto pointed out that when ABS is done for one direction signaling on each track of double track, it does read two blocks ahead. However, where ABS is set up for bidirectional operation, e.g. single track, overlap is used, so more than the two blocks ahead are read, thus protecting against head on collisions. APB is an alternate solution for single track.)
APB (Absolute Permissive Block) accounts for this, so that when a train enters single track, it tumbles-down all the opposing signals to red, so that a train in the opposite direction cannot (by rule at least) enter that territory and cause a head-on.
For an example of ABS vs. APB signaling, visit Logic Rail Technologies APB demo.
So how does this apply to the NEB&W? We will be copying the D&H system as closely as possible, with CTC control from Alburgh (north fiddle yard) all the way to the Green Island Bridge. The double-track main will be signaled in both directions. The wye and the rest of Troy will be controlled by the Troy tower operator (posing as all four operators) on a similar CTC-style panel. The signals in Troy are all Semaphore signals.
There are numerous speeds in the descriptions of the signals, so here is a quick overview.
Normal Speed - The maximum authorized speed (by timetable).
Limited Speed - Not exceeding 45 mph for passenger, 40 mph for freight.
Medium Speed - Not exceeding 30 mph.
Slow Speed - Not exceeding 15 mph.
Restricted Speed (Rule 80) - Movements made at Restricted Speed must apply the following three requirements as the method of operation:
- Control the movement to permit stopping within one half the range of vision short of:
- Other trains or railroad equipment occupying or fouling the track.
- Switches not properly lined for movement.
- Derails set in the derailing position.
- Any signal requiring a stop
- Look out for broken rail and misaligned track
- Do not exceed the maximum speed prescribed by timetable or other written directives, not exceeding 20 mph outside interlocking limits and 15 mph within interlocking limits.
Apparently the D&H did not use slow interlockings, so we have no Slow Speed signals. As always, timetable speed overrules the speed listed here. So if you are in 25 mph territory and get a signal dictating medium speed, you cannot increase to 30 mph unless the timetable speed increases to 30 mph or greater at that signal.
Aspects, Rules, and Indications
As I said before, the three-headed signals can have up to 27 different aspects!! Fortunately, we only use about 6-10 of them. All the aspects, the matching rule, and what the indication is (plain English) are below. Signals with a number plate are permissive (meaning you can stop then proceed at restricted speed).
Also see this section.
Rule 281: Clear
Proceed not exceeding Normal Speed.
You have no trains in front of you for at least two blocks, get a move on at maximum allowed timetable speed!
Rule 285: Approach
Proceed prepared to stop at the next signal. Trains exceeding Medium Speed must begin reduction to Medium Speed as soon as the engine passes the Approach Signal.
The second block in front of you is occupied, slow down and be ready to stop at the next signal.
Rule 291: Stop and Proceed
Stop, then proceed at Restricted Speed until the entire train has passed a more favorable signal.
You can pass this signal after you stop. This requires the number plate to be on the signal. Usually it means you are following another train too closely.
Rule 282a: Advance Approach
Proceed prepared to stop at the second signal. Trains exceeding Limited Speed must begin reduction to Limited Speed as soon as engine passes the Advance Approach Signal.
This means the third block in front of you is occupied. So you have to slow down a little. This will only be used if a block is really short, if it is a downgrade section of track, or a combination of the two.
Rule 282: Approach Medium
Proceed approaching the next signal at Medium Speed.
This is used at a distant signal, and it usually means you will be taking the diverging route at the next interlocking (i.e. taking a siding). So slow down a little since you will have to be going through a turnout.
Rule 292: Stop Signal
Pretty simple here, stop and hold until you get a better signal.
Rule 283: Medium Clear
Proceed at Medium Speed until entire train clears all interlocking or spring switches, then proceed at Normal Speed.
This is the usual signal at the end of a siding. It means you can leave the siding not going too fast (you are going through a turnout) and then speed up to timetable speed once you are clear.
Rule 286: Medium Approach
Proceed prepared to stop at the next signal. Trains exceeding Medium Speed must begin reduction to Medium Speed as soon as the Medium Approach signal is clearly visible.
Also typically used at the end of a siding, it means you are coming off a siding and will stop at the next signal. Again, you are following too close to the train in front of you.
Rule 283a: Medium Approach Medium
Proceed at Medium Speed until entire train clears all interlocking or spring switches, then approach the next signal at Medium Speed. Trains exceeding Medium Speed must begin reduction to Medium Speed as soon as the Medium Approach Medium signal is clearly visible.
The most confusing of all! This means you are diverging through a turnout, so go slow through that. Then it acts as a regular Medium Approach signal, telling you that you are most likely diverging at the next interlocking. This is a distant signal for the next interlocking. An example would be running through a siding (not stopping at the end) or the signal before going onto a branch line.