RR Signal Aspect Speed Table (N. America)

RR Signal Aspect Speed Table (N. America)


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RR Signal Aspect Speed Table (N. America)


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Comments, additions, corrections, criticisms.


Purpose

This document is meant as an adjunct to the Learning the Aspects document. This document may be used as a brief review of what the signal aspects mean operationally, to the engineer. The basic rules of how signals are named is described in Learning the Aspects.

Notes

Aspects named with the word "Diverging" are not considered, as they are merely a trivial (simpler) case of what is described. In all such "diverging" cases, the actual speed permitted must be looked up in the Employee Timetable and Special Instructions (ETT), or equivalent source, if it has not been memorized.

Speeds marked with an asterisk (*) are historically later additions to the rules. These additions were made to prevent the practice known as "riding the yellows" and to enforce a reasonable, lower speed between 2 signals, both of which are more restrictive than maximum allowed speed. For example, the Approach signal initially carried an indication only of "Approach the next signal prepared to stop." As one too many instances occurred wherein an engineer passed the Approach signal, yet continued at too great a speed to stop at the next signal, this aspect was amended with the text "Train exceeding Medium Speed must at once reduce to that speed." Soon, any signal implying a stop at the next signal was modified to require Medium Speed in the intervening block. Similarly, any signal implying a stop at the second signal was modified to require Limited Speed in the intervening block - a logical extension.

The author personally feels that the speeds shown with the asterisks (*) are inherently safer than those without asterisks. The logical extension of this view is that aspects such as Limited Approach (Limited to Stop) are, at best, of questionable utility, at worst, downright unsafe.

The new Canadian names are given only partly for completeness. I trust the reader will find how wonderfully descriptive these aspect names are of the actions required of the engineer. My only complaint is that the aspect names intermix block condition ("clear") with speeds; "Full to Stop", I think, would have been a better name.

Finally, note that this table is a generalization of "good practice". Specifics varied from railroad to railroad, from rule system to rule system, and from year to year. I have seen rules specifying that the speed reduction mandated by a signal aspect must be started as soon as the aspect is seen; at the signal; and as soon as the head end of the train passes the signal. In short, check your rule book.

Legend

Full
Maximum permitted speed; this speed is found in the ETT
Cab Speed
70 or 80 MPH
Limited
40 or 45 MPH (varies)
Medium
30 MPH
Slow
15 MPH
Restricting
Varies among roads. Generally 15 MPH or less, watching out for broken rail, obstruction of track [by train or otherwise], switch not properly lined, and prepared to stop with 1/2 the range of vision. Some RRs create a new "Controlled Speed" category and have slightly different criteria for Restricting vs. Controlled.
n/a
Not applicable. Does not apply to the given case.
---
Uknown, uncertain, etc.

Aspect Speed required NOW Speed through interlocking Speed through block beyond interlocking Speed required at next signal Speed required at 2nd signal Blocks known clear
Stop Stopped n/a n/a n/a n/a unknown
Stop-and-proceed
at an automatic signal or a fleeted interlocking signal
Stopped --- Restricted Restricted, prepared to stop n/a 0
Variable amounts of time stopped are required, from 0 to 3 minutes.
Stop-and-proceed
at an interlocking signal
Stopped Restricted Restricted Restricted, prepared to stop n/a 0
Restricting
Restricted Proceed
Restricted varies Prepared to stop. n/a n/a unknown
Restricting is often used for trains proceeding from signalled to unsignalled track. In such a case, the speed allowed on such track will govern beyond interlocking limits. Restricting is also used to run a train "against the current of traffic", i.e., the "wrong way" on unidirectionally signalled track. In such a case, the speed allowed under Manual Block rules governs.
Approach
Clear to Stop
Full (Full) Full/Medium*
prepared to stop
Stopped n/a 1
This signal may be received at an interlocking or an automatic signal. "(Full)" denotes the speed required should this signal be received at an interlocking signal.
Advance Approach
Advance Clear to Stop
Full (Full) Full Full/Medium* Stopped 2
Clear
Clear to Clear
Full (Full) Full Full n/a 2
Aspect Now Thru intlk Block beyond Next signal 2nd signal Clear blks
Approach Slow
Clear to Slow
Full (Full) Full/Medium* Slow n/a 2
Approach Medium
Clear to Medium
Full (Full) Full/Limited* Medium n/a 2
Advance Approach Medium Full (Full) Full Full/Limited* Medium 3
Approach Limited
Clear to Medium
Full (Full) Full Limited n/a 2
Aspect Now Thru intlk Block beyond Next signal 2nd signal Clear blks
Slow Clear
Slow to Clear
Slow Slow Full Full n/a 2
Slow Approach
Slow to Stop
Slow Slow Full/Medium*;
prepared to stop
Stopped n/a 1
Slow Approach Slow
Slow to Slow
Slow Slow Full/Slow* Slow n/a 2
Slow Approach Medium
Slow to Medium
Slow Slow Full/Medium* Medium n/a 2
Slow Approach Limited
Slow to Limited
Slow Slow Full/Limited* Limited n/a 2
Aspect Now Thru intlk Block beyond Next signal 2nd signal Clear blks
Medium Clear
Medium to Clear
Medium Medium Full Full n/a 2
Medium Approach
Medium to Stop
Medium Medium Full/Medium*;
prepared to stop
Stopped n/a 1
Medium Advance Approach Medium Full/Limited* Full/Medium*
prepared to stop
Stopped n/a 2
Medium Approach Slow
Medium to Limited
Medium Medium Full/Medium* Slow n/a 2
Medium Approach Medium
Medium to Medium
Medium Medium Full Medium n/a 2
Medium Approach Limited
Medium to Slow
Medium Medium Full Limited n/a 2
Aspect Now Thru intlk Block beyond Next signal 2nd signal Clear blks
Limited Clear
Limited to Clear
Limited Limited Full Full n/a 2
Limited Approach
Limited to Stop
Limited Limited Full/Medium*;
prepared to stop
Stopped n/a 1
Limted Approach Slow
Limited to Slow
Limited Limited Full/Medium* Slow n/a 2
Limited Approach Medium
Limited to Medium
Limited Limited Full/Limited* Medium n/a 2
Limited Approach Limited
Limited to Limited
Limited Limited Full Limited n/a 2


Mark D. Bej, M.D.
bejm@ccfadm.eeg.ccf.org
+216-444-0119
1997.03.31