Forms of (Color-) Position Light Signals

Forms of (Color-) Position Light Signals

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Forms of Position Light Signals


Notes

  1. The color light signals in the first column are provided for reference and represent "typical" US practice only, not necessarily that of any one railroad.

  2. Signal category names are logical groupings of a given style and are not meant to indicate the the railroad whose name is used for the category used all of the signal forms shown. For example, Conrail added certain position-light aspects; these are shown under "PRR" because the basic style remained unchanged. Amtrak's colorization of PRR signals, however, constitutes a basic style change and is thus classified separately.

  3. Some signal forms shown may have been restricted only to certain territories of the railroad. Examples are the "red-eye" PRR signals, unused or essentially unused east of Harrisburg; and the "red-eye" pedestal PRR signals.

  4. Other railroads used PRR-style and B&O-style signals. Examples include the use of PRR-style signals by the Lehigh Valley and Norfolk & Western; and the use of B&O-style signals by the Alton. When sufficient information is gathered, they will be added. Use by these other railroads may have been identical to that of the originator, or may have varied.

  5. Signal faces are typical but not exclusive usage and are considered insignificant indicators of aspect, except for the purpose of orienting the viewer of the signal to the expected location of the signal lamps. E.g., a round face may have been used in places where the sides-cut-off face is shown, and so forth.

  6. Further, beware somewhat in some cases of rulebooks. The N&W rulebook has shown dwarves with square faces, though none such existed. This was (apparently) done as a generalization, so that the rulebook did not have to be specific as to the actual shape of the dwarf.

  7. Specific notes on the various railroads' usage:
    PRR
    Upper signal face always round and always present. Rare exceptions to latter are found only in areas of very close clearance (e.g. Pennsylvania Station, Newark, N.J.; Delair Bridge, N.J.). Lamp spacing 18" (46cm) for both arms, with rare exceptions in close clearance areas.

    Lower signal face extremely variable. When a full lower face is present, this is always the straight-sided version (later Conrail and SEPTA laziness, e.g. BANKS interlocking, notwithstanding). The full straight-side face was often (?usually) used when a complete lower arm was present. The oblong oval face was nearly always used, oriented vertically, when only the vertical aspect was present on the lower arm (e.g. distant signals); and often, but less frequently, oriented diagonally, when a single diagonal aspect was present on the lower arm. However, partially to fully loaded lower arms have been seen with the full face, with the oblong face only, or with no face. I've never seen a diagonal oblong face when a lower vertical aspect was present

    When only a single lower marker is present, there is no face. I can't recall ever seeing either the full or oblong face of whatever orientation. An exceptional case may have existed where a patial lower arm was downgraded to a marker alone. The lamp assembly, lenses, hood are otherwise identical to those used in upper arm.

    Unused locations in the signal face are covered by a small round plate; middle lamp of upper arm is absent when unneeded (e.g. "red-eye" home signal governing no straight route). PRR proper (i.e., pre-1968) used flashing lamps only for Medium Approach so far as I can tell, and the lower triangle for Limited. Flashing for Limited Speed aspects appears to be a later addition.

    Signals on signal bridges were installed with the upper arm above the top deck; the lower arm between the 2 decks and in front of the signal bridge. Number plates were installed on automatic signals and absent (except for a few exceptions) on interlocking signals. Interlocking signals frequently had their number spray-painted on in a location inconspicuous to the engineer (driver); this was for ease of identification in large interlocking plants. This was the 'standard' or most common; there are/were definite exceptions when needed for visibility. Signals on masts could be of various heights, again apparently adjusting for visibility; I do not know of definitive cases where signals were deliberately placed at different heights so as to convey any meaning (compare N&W, below).

    PC
    First placement of a PRR signal to the left of the track it controls (so far as I am able to tell; Williamsport-Buffalo main line, 1967). First (?) placement of 2 PRR signals on a bracket post (CP-Lake, Indiana).
    CR
    Acquired legacy of signalling of multiple roads, including PRR. Added flashing to Limited Speed aspects (or Penn Central?). Several installations of 2 round signal faces, rather than a round and a flat-sided one. Removed lower marker from automatic signals circa 1983. By CR's rules of that time (and present; and even prior PRR rules), the marker lamp duplicated the function of the number plate, i.e., identifying the signal as an automatic signal. CR, since 1986 has been replacing PRR-style by color light signals. First installations were wholesale replacements of entire lines (Vandalia line across Illinois; Trenton Cutoff) or replacements in interlockings immediately abutting color-light territory (e.g. HARRIS, Harrisburg, Pa.). Early preference was for Michigan Central-style, small-faced searchlight signals. More recently replacements are piecemeal, one side of an interlocking, or even only part of one side of an interlocking. All recent replacements are with Type G (3 lights in triangle) faces.

    N&W
    Basic signal appearance exactly like PRR's, from which these are derived. Initially used all amber lights, as PRR. Later (?1960s) colorized. Note N&W is the only major eastern road to use (weak) route signalling. Also note the use of the solitary lower marker to indicate Stop, in contrast to Stop and Proceed as with PRR and B&O. The "S" plate is used as a backup to indicate an absolute signal. The other "basic" and "interlocking home" aspects were seen, of course, with the "S" plate, but the indication was not changed thereby. This table follows the N&W rulebook practice of showing the "S" only with the Stop and Stop-and-Proceed aspects.

    N&W consistently used round signal faces on both arms; I am not aware of any straight-sided lower-arm faces. Solitary markers used no face. N&W broke with PRR practice of always using the full, round face for the upper arm, particularly on signals that only had the 2 reds on that arm: the oblong face (used by PRR on the lower arm) was often used. I am much less certain of the use of the oblong face on the lower arm.

    N&W signals show an interesting evolution through the rulebooks. The lower marker appears to have been used solely to designate the signal as an interlocking signal. This is not explicitly stated in the rulebook, but follows from the aspects with which this marker is associated. Presently, N&W signals are being replaced with SOU-style 3-light color light signals.

    AMTK
    Amtrak acquired a major legacy of PRR signalling. Began colorization as an experiment on S/B distant signal to PRINCE interlocking in 1988, then colorized in earnest soon after NEC track/signalling upgrading began. Current AMTK yellow is darker in hue than previous PRR amber. Green is very bluish, like many "green" highway traffic lights. Colorized signals lose their middle lamp on the upper arm. I've seen some signals colorized, others not, on the same signal bridge; though I've not seen, and the rulebook would not support, a signal with one arm colorized, the other arm not.

    B&O
    Signal lenses are larger then PRR, signal face is smaller, and lens hoods are shorter. Face is always present; marker lamps each have small faces. Placement of 2 fully-loaded B&O signals on a bracket post can be problematic because of the marker lamps being closer to each other than to the main signal face. Usage of Stop-and-Proceed varied, with the 2 versions sometimes providing route semantics. Such usage appears to have been intentional, though having the status of "local color" (i.e., present on the signal engineer's drawings, but not in a Rule or Special Instruction). Signals in older installations were generally (always?) to the right of the governed track (easy because most B&O trackage was unidirectionally signalled); presently usage varies. Liberal use of bracket posts.

Signalling Styles


The Basic Aspects.

Of these aspects, Clear, Approach, and Stop-and-Proceed are generally seen at automatic (block) signals. Some roads used Advance Approach also, some used Approach Medium in identical settings, and some did not use this concept at all. Stop signals are found only at interlockings or other such controlled locations. Restricting is generally used at interlocking (controlled) signals for trains proceeding into unsignalled territory (either entirely unsignalled, or unsignalled for that train's direction of travel). Some exceptions exist (e.g. the eastern grade via Horse Shoe Curve).

Clear
typ. CL PRR
281
N&W
281
B&O
281
AMTK
281
Advance Approach
typ. CL PRR N&W
282A
B&O AMTK
282A
Approach
typ. CL PRR
285
N&W
285
B&O
285
AMTK
285
Stop
typ. CL PRR
292
N&W
292
B&O
292
AMTK
292
Stop-and-Proceed
typ. CL PRR
291
N&W
291
B&O
291
AMTK
291
Restricting
typ. CL PRR
290
N&W
290
B&O
290
AMTK
290

Interlocking Signal Aspects

(Nearly) all of the speed-signalling aspects are named with a speed first, indicating the speed at which the train must be travelling immediately (through the switches of the interlocking). The second word provides block occupancy information, clear indicating at least 2 free blocks, approach indicating no more than 1 such free block.

Route-signalling aspects, because of their lack of need to provide speed information, the number of aspects is greatly reduced.

Cab Speed
typ. CL PRR N&W B&O AMTK
281A
--- --- ---
Limited Clear
typ. CL PRR N&W B&O
281C
AMTK
281C
---
Limited Approach
typ. CL PRR N&W B&O
281D
AMTK
--- --- ---
Medium Clear / Diverging Clear
typ. CL PRR
283
N&W
283
B&O
283
AMTK
283
Medium Approach / Diverging Approach
typ. CL PRR
283A
N&W
286
B&O
286
AMTK
286
Slow Clear
typ. CL PRR
287
N&W
287
B&O
287
AMTK
287
Slow Approach
typ. CL PRR
288
N&W
288
B&O
288
AMTK
288

Distant Signal Aspects

(Pardon the possibly loose usage of the word 'distant'.) Used in advance of the interlocking signals above, to warn the engineer of the speed or route required at the following signal. All are named "Approach" with the speed or route as the last word (cf above). In a sense, all could be named "Full ..." if one wished to create a "fully qualified" name.

Approach Limited
typ. CL PRR N&W B&O
281B
AMTK
281B
---
Approach Medium / Approach Diverging
typ. CL PRR
282
N&W
282
B&O
282
AMTK
282
Approach Slow
typ. CL PRR
284
N&W B&O
284
AMTK
284
---

Combination aspects.

These aspects are used at interlocking signals (as evidenced by a speed being the first word), generally in territory with either high traffic levels or with closely spaced interlockings or junctions. Each signal is effectively a combination of an interlocking signal (3 lists above) with a distant signal (2 lists above).

Limited Approach Limited
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Limited Approach Medium
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Limited Approach Slow
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Medium Approach Limited
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Medium Approach Medium / Diverging Approach Diverging
typ. CL PRR N&W
283B
B&O
283A
AMTK
--- ---
Medium Approach Slow
typ. CL PRR N&W B&O
283B
AMTK
--- --- ---
Slow Approach Limited
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Slow Approach Medium
typ. CL PRR N&W B&O AMTK
--- --- --- ---
Slow Approach Slow
typ. CL PRR N&W B&O
287A
AMTK
--- --- ---

Manual Block Aspects

These signal aspects provide block information which is "manually" known (i.e., by the operator talking to other operators or a dispatcher). No speed information is given.

Clear Block
PRR
280
B&O AMTK
Permissive Block
PRR
289
B&O AMTK

Special-Use Aspects

These aspects utilized the same signal forms as those above but generally provided "special" information.

For example, the Caution (etc.) aspect only warns of an upcoming signal (generally an interlocking signal) but specifically diavows providing any block occupancy information. It is most often used when exiting dark territory into signalled territory, when the expense of a block circuit immediately prior to entry into interlocking limits cannot be justified or is not desired. In application by the train engineer (driver), I'm not sure how it's any different from Restricting. In application by the signal engineer, Caution tended to be used upon imminent entry into signalled territory, whereas Restricting tended to be used upon immenent exit from such territory. Caution has been extensively used by Conrail on the former PRR main line across Indiana, where the engineer encounters a number of automatic interlockings, but the line is otherwise unsignalled. All distant signals (signals immediately in the rear of the interlocking home signal) are fixed at Caution (Approach Restricting). Home signals at these interlockings are actuated by the presence of the train, so a block circuit is present, but may not extend a full braking distance to the previous Caution signal.

The Phase Break signal is placed in advance of the catenary phase break. If the 2 power supplies on opposite sides of the phase break become sufficiently out of phase, the phase break (an independent stretch of catenary wire) is de-energized and the phase break signal lights. A set of 4 of these may be viewed in downtown Philadelphia, always lit because of the de-energized phase break between the former Reading RR and former Pennsylvania RR electrical power territories. Note this is a new installation by SEPTA, and not a PRR installation. Not far from Philadelphia, in Thorndale, is another installation, but these are normally dark. Phase Break signals have no faces.
Approach Clear
PRR B&O AMTK
293B
(semaphore/ color light version only)


Caution /
Approach Restricting /
Distant Signal
PRR
285A
B&O AMTK
293C
(semaphore form only)


Take Siding
PRR B&O AMTK


Phase Break
PRR B&O AMTK


Switch Open
PRR B&O AMTK
293B


Switch Closed
PRR B&O AMTK
293B


Slide Protection
PRR B&O AMTK
293B


Mark D. Bej
bejm@eeg.ccf.org
+1 216-444-0119
1999-01-22