Wednesday, February 29, 2012


Tim commented on my post about CEFX 1050 and the sunset, asking if my interpretation of the red-over-green-over-red was correct. I had said it was "LIMITED TO CLEAR" (Canadian Rail Operating Rules #416) but he pointed out (correctly) that it would be that only if there was an "L" plate on the signal mast. If the "L" is missing then it is rule 422, "MEDIUM TO CLEAR". The difference is only in the speed limit. LIMITED=45 MPH and MEDIUM=30 MPH.

I looked at signal 112 today and it does not have any plate on it, so a red-over-green-over-red indication on that signal means MEDIUM TO CLEAR.

I had a look at the detailed track diagram for the area, "CP MAKWA".
The signal I was talking about was 112, the three headed signal facing west. The crew would have seen signal 134 first, and I believe it was showing green over red, rule 405, "PROCEED" it should have been showing yellow over green, rule 407, CLEAR TO MEDIUM.

Signals are numbered by mileage, with an implied decimal point to the left of the last digit. So signal 112 is at mile 11.2 and signal 134 is at mile 13.4. In cases where there are more than one track, the track name is appended, like 111N and 111S.

The mileage is not precise because you could have two signals facing opposite directions on the same mast, but they have different numbers. For example, signals 133 and 134 could be on the same mast (they aren't).

When the Rail Traffic Controllers (RTCs) give out blocks to maintenance crews, they often use signals to indicate the limits of the authority they are giving. For example, "from signal 133 to signal 112".

While doing the research, I found an interesting article on Canadian signals. Check it out!

EDIT: Thanks Jeff Keddy for pointing out what signal 134 should have been showing.


Tim said...

Cool! Thanks for taking my comments under consideration. I was interested to see whether it did have the "L" plate or not. Where did you get that nice track diagram? That is pretty cool.


Steve Boyko said...

The diagram is from the CP employee timetable for the region.

Tim said...

Never seen that in other CP ETTs unfortunately. Would like to have that for some of the other lines. Very cool!