Ontario...
Posted Speed/Safe/Risky
80/90/100
90/105/110
100/115/120
Keep in mind, especially in the more remote parts of Ontario, police are spread very thin. If its overcast and your between towns with a police station and not on a major hwy (17/11/7/400 series) you can safely push the upper end of those numbers.
Oh, one last thing, 50 over they will seize your vehicle on the side of the road and suspend your liscense for a week with upto a $10,000 fine.... which if you think about it is a bit on the ridiculous side for what amounts to 30 over,
Watch yourself between dusk and morning. Lots of animals. Most of the hwys are cleared of brush back a pretty good amount so unless something big is really hauling ass, you'll at least get a visual to give yourself a fighting chance.