My guess would be

My guess would be kilometers,

S

Light, Rapid, Comfortable

The LRC trains (Light, Rapid, Comfortable) were used in Ontario and Quebec starting in 1975, so it's a good chance that this sign is miles per hour. I remember when Canada made the switch to metric, around 1980, while I was in college in Potsdam, NY.

These were locomotive hauled trains, and the locomotives and cars used lightweight, aluminum construction. This reduced the side force on the rails, which combined with the active tilt system (later used in the Acela trains on Amtrak), allowed higher speed in the curves and faster acceleration. There is a Wikipedia article on these.

When the locomotives were replace, they used standard steel construction, and the tilt systems on the cars were disabled. This limited their speeds to be the same as  conventional passenger trains.

Ken Goslett has a good video on these trains on TMTV.

90kmh is about 55mph

so makes sense that it is in metric units.

Canada is metric yes...

However this is in miles per hour (MPH). The LRC was (when pulled by the LRC loco) regularly running ast 100 mph (160 Kilometers per hour)

Yes on the railroad these sign were/are still in mph.

Interesting

thanks for correction.  

Timing is everything - maybe

As the sign/picture is from 1975 before Canada switched to the metric system in mid-70s to mid-80s (like when US was supposed to switch), makes sense they are MPH.  However, according to the wikipedia article on metrication in Canada the railroads still use miles and mph today.

https://en.wikipedia.org/wiki/Metrication_in_Canada, scroll down to Common Usage Today.

Kinda

Canada, like the rest of the world, use the metric system.  In Canada some railroad signage is still in the old system, like  MPH .

Kilometers. meters, liters and kilogram, is applicable to the railroad as well. Now whatever they want to use on their right of way...

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Most of this has been covered already, but some posts seem to ignore information given before them, so, to clarify:

1) LRC stands for "Light-Rapid-Comfortable". They are NOT light-rail, self-propelled passenger cars. They were "standard" locomotive-hauled trains, but the equipment was all purpose designed for 100MPH high-speed rail. The unique locomotives have all been long retired, but all the coaches are still in daily use on VIA trains in the Windsor-Toronto-Montreal corridor.

http://en.wikipedia.org/wiki/LRC_(train)

2) As stated, regardless of the dating of the photo, and despite Canada using metric in most uses, the railways all still uses miles. (There might be one little obscure shortline somewhere that actually replaced mile markers with km, but 99% use miles.) The signs are in miles per hour, not kilometers.

3) The bottom sign is correctly identified as indicating 90 MPH speed limit for most passenger trains, and 60 MPH for freights. The LRC trains discussed above were designed for higher speed operation than the "conventional" trains still using coach stock and locomotives from the 1950s, so they got their own special speed sign above the normal speed limit sign.

4) These LRC speed signs were only found on the CN main line between Toronto and Montreal.