User:Dp67/Sandboxes/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.
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.
- 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.
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.
| 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. |
|
| 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. |
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.
Notes and references
- The Pennsylvania Railroad rules for conducting transportation, October 28, 1956
- The Pennsylvania Railroad rules for conducting transportation, April 28, 1968
