North American railroad signals

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Main article: North American railway signaling

A drawing of a complete B&O style signal head. (Lights Out)

This article describes the operating procedures of North American railroad signals on railroads which are members of, or compliant with, the Northeast Operating Rules Advisory Committee (NORAC).

This article will explain some of the aspects of railroad signaling. For a more technical look at how signals actually work, read North American railway signaling.

NORAC standardized aspects in the northeast portion of the USA to alleviate confusion because the amount of differing aspects between the many original railroad companies after the many mergers beginning in the 1960s.

North American railroads are not required to be members of NORAC, and most western railroads have a substantially different aspect system. Canadian railways are subject to a standardized set of operating rules and aspects which is also unrelated to NORAC.

• The railroad signals of North America can be broken down into three basic types of signals.
  • Color - The 5 colors used are: red, yellow, green, white (used as a modifier) and sometimes blue and purple. Each color of the signal indicates one procedure, Red = stop, yellow (or amber) = caution, green = proceed. White is used as a modifier, for example, a red light would normally mean stop. Adding a white light to the red signal could mean stop and proceed. Or a white light with a green could mean proceed at a restricted speed.
  • Position - A single color may be used for all rules whereas the position of the lights describes the proper procedure.
  • Color-Position - a combination of the two methods above whereas colors are used in various positions to describe the proper procedure.

[edit] Signals and aspects

Note: Images are placed side by side for a clearer perspective on the possible light configurations. Under normal conditions there may only be one or two light trees. There are also two different types of signals shown here. The stick lights, and the large round lights are 2 different designs that would not normally be seen together.

Rule number	Rule	Rule description and procedure	Signal aspect
281	Clear	Clear to proceed at normal track speed.
281(b)	Approach Limited	Proceed to next signal at limited speed.
281(c)	Limited Clear	Limited Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed.
281(d)	Limited Aproach	Limited Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed, prepared to stop at next signal.
282	Approach Medium	Proceed, approaching next signal not exceeding Medium Speed.
283	Medium Clear	Medium Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed.
283(a)	Medium Approach Medium	Medium Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed approaching next signal not exceeding Medium Speed.
283(b)	Medium Approach Slow	Medium Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed approaching next signal not exceeding Slow Speed.
284	Approach Slow	Proceed, approaching next signal not exceeding Slow Speed.
285	Approach	Proceed prepared to stop at the next signal. Trains exceeding medium speed must immediately begin reduction to medium speed as soon as the engine passes the Approach Signal.
285(a)	Distant Signal	Approach next signal prepared to stop. NOTE: This signal provides information only about the next signal, not conditions of the track ahead.	(semaphore)
286	Medium Approach	Medium Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed prepared to stop at next signal.
287	Slow Clear	Slow Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed.
287(a)	Slow Approach Slow	Slow Speed through turnouts, crossovers, sidings, and over power-operated switches; then proceed approaching next signal not exceeding Slow Speed.
288	Slow Approach	Slow Speed through turnouts, crossovers, sidings, and over power-operated switches; then� proceed prepared to stop at next signal.
290	Restricting	Proceed at Restricted Speed.
291	Stop	STOP, then proceed at Restricted Speed.
292	Stop	STOP.
295	Approach	Proceed, approaching next signal as authorized by the aspect displayed. If signal is dark, proceed prepared to stop at next signal until it can be plainly seen that indication of next signal allows train to proceed.	Signal, black, APP on round white marker below
296	Doll Arm	A track intervenes between the signal and the track governed by the signal.
297	Adjacent or Bracketed Signals	Proceed, approaching next signal as authorized by the aspect displayed. If signal is dark, proceed prepared to stop at next signal until it can be plainly seen that indication of next signal allows train to proceed.
298	Grade	Proceed at Restricted Speed.

[edit] Distant (approach) signals

A distant signal can either be an automatic signal before an interlocking, or the interlocking signal itself when interlockings are back to back. Distant signals typically display more aspects than a typical block or interlocking signal to warn trains of diverging movements at the next interlocking however this is not always the case if there are no diverging paths available.

Distant signals are often referred to as Approach Signals as the signal block before the interlocking is known as the approach block. When a train enters the approach block any route lined up at the interlocking will become locked in place until a timer is run to prevent routeing a conflicting movement without giving the approaching train adequate time to come to a stop.

A pair of distant signals on the NJT RiverLINE light rail. Note the 'D' boards placed in accordance with the NORAC Delay in Block rule

In the aftermath of the 1996 Silver Spring Collision the Federal Railroad Administration amended its regulations for push-pull train operation to prevent locomotive engineers from forgetting that they were approaching a stop signal after making a station stop. The resulting Delay in Block Rule required that all distant signals in territory where push-pull trains operated in the absence of cab signals were to be marked with a 'D' placard to remind engineers that they were bound by a 40mph speed restriction between any station stop and the point where the home signal became visible.

[edit] Definitions

Absolute Block - a block that may be occupied by only one train at a time.

Absolute Signal - a color light, color position light, or semaphore signal without a number plate, "P" marker, APP" marker, "C" marker, or "G" marker, that conveys Stop as its most restrictive aspect. Automatic Block Signal System (ABS)- a series of consecutive blocks whose use is governed by train[-]actuated block signals or by certain conditions affecting the use of a block. Unless so specified, such signals do not authorize the movement of trains.

Block - a track section of defined limits. In signaled territory, a block is the track section between two consecutive block signals governing movements in the same direction. It is also the track section from a block signal to the end of signaled territory.

Block Signal - an absolute or intermediate signal at the entrance to a block that governs the movement of trains using that block.

Color Light Signal - a fixed signal that displays aspects by the color of a light. It may also display aspects by a combination of colored lights.

Color Position Light Signal (CPL) - a fixed signal that displays aspects by the color or position of two or more lights.

Current of Traffic - the movement of trains on a main track, in one direction, as specified by the rules or special instructions.

Direct Traffic Control Block - a block whose use is governed by verbal authority of the train dispatcher.

Fixed Signal - a permanent signal or sign indicating a condition affecting train movement.

Interlocking - an arrangement of interconnected signals and signal appliances for which interlocking rules are in effect. Signals and movement of signal appliances must succeed each other in proper sequence.

Interlocking Signals - fixed signals of an interlocking.

Intermediate Signal - a block signal equipped with either a number plate, a "G" marker, or "P" marker. It conveys Stop and Proceed at Restricted Speed as its most restrictive indication.

Main Track - a track extending through yards and between stations. It is other than an auxiliary track.

Siding - an auxiliary track for meeting or passing trains. It is designated in special instructions.

Traffic Control Signal System (TCS) - a signal system under which opposing and following train movements are authorized and governed� by block signals.

Train - an engine, with or without cars, displaying a marker.

[edit] Sign post signals

[edit] Speeds

Rule number	Rule	Rule description and procedure	Signal aspect
297	Controlled Speed	a speed that will permit stopping within one-half the range of vision. It will also permit stopping short of a train, a car, an obstruction, on-track equipment or a stop signal.
298	Limited Speed	a speed not exceeding 45 miles per hour. Shown here are: (A) advanced warning (B) limited speed zone indicator.	(A) (B)
298	Medium Speed	a speed not exceeding 30 miles per hour.
298	Restricted Speed	a speed that will permit stopping within one-half the range of vision. It will also permit stopping short of a train, a car, an obstruction, on-track equipment or a stop signal, a derail, or an improperly lined switch. It must permit looking out for broken rail. It will not exceed 15 MPH. The limit signs are marked with S and the resume speed signs are marked with the letter R. (A)Advance warning of restricted speed. (B) Restricted speed. (C) Temporary restricted speed. (D) Resume speed. (E) Resume speed from temporary restriction.	(A)(B) (C)(D)(E)
298	Slow Speed	a speed not exceeding 15 miles per hour.

[edit] Other forms of signals

- Whistle posts are marked with a "W" signaling the engineer to begin, or prepare to sound the horn.

Rule number	Rule	Rule description and procedure	Signal aspect
14(l)	Whistle post	a warning signal for the engineer of a train that he/she is approaching a road crossing, or "Grade crossing" as they are often called. See also: Whistle post

[edit] References

• The Pennsylvania Railroad rules for conducting transportation, October 28, 1956
• The Pennsylvania Railroad rules for conducting transportation, April 28, 1968