The Meaning Of NORAC Signals
Quick Reference Guide
Version 0.2 (6/08) -- Copyright © 2008 Deltareum. All rights reserved.
Comments welcome. Email George at deltareum (at) yahoo (dot) com.
The following are simplified definitions of signal terms, but not the actual NORAC definitions.
Signal aspect is the way a signal looks.
Signal name is what the signal is called.
Signal indication is what the signals indicate to us to do.
Again, the meanings of signals are explained in plain language. They are not the actual indications.
There are basically three types of signals:
Stop Signal = Stop.
Stop And Proceed = Come to a complete stop first, and then proceed, but at Restricted Speed.
Restricting = Proceed at Restricted Speed.
Approach = Approaching a Stop Signal, begin to slow down to 30mph.
Advance Approach = Advance warning of an Approaching Stop Signal, two signals down. Also start slowing down.
Medium Approach = Regulate your speed to Medium (30mph), while you are Approaching a Stop Signal (or Stop and Proceed).
Slow Approach = Regulate your speed to Slow (15mph), while you are Approaching a Stop Signal (or Stop and Proceed).
First come the Clears:
Clear = Proceed, all's clear ahead.
Limited Clear = Proceed at Limited Speed (45mph), it's clear ahead.
Medium Clear = Proceed at Medium Speed (30mph), it's clear ahead.
Slow Clear = Proceed at Slow Speed (15mph), it's clear ahead.
Cab Speed = Proceed at the Cab-Signal-Apparatus-indicated speed.
Signals that bring your speed down:
Approach Limited = Approaching a signal that requires Limited Speed.
Approach Medium = Approaching a signal that requires Medium Speed.
Approach Slow = Approaching a signal that requires Slow Speed.
Medium Approach Medium = Proceed at Medium Speed and Approach the next signal at Medium Speed also.
In basic terms the following math equations are true:
Medium Approach ≅ Medium Clear + Approach.
Slow Approach ≅ Slow Clear + Approach.
Medium Approach Medium ≅ Medium Clear + Approach Medium.
The symbol “≅” means "approximately equal," as the indications do not match exactly.
On our territory, you may also see this one:
Clear To Next Interlocking = No train up ahead of you and it's Clear until the Next Interlocking.
This concludes the discussion on the meaning of signals. Signal Progressions explains how signals are used with each other.