Gotta argue with you there, bud, at least as it relates to northern Ontario, as well as western Ontario areas such as Grey, Bruce and Huron and Perth counties. Highway are typically closed preemptively. The primary driver is visibility. I don't know what the practice is now but when I worked up there, when the MTO pulled its trucks because they simply can't see, the signs went up. It is mostly caused by blowing snow but there were a couple of spots along Superior where simply 'precipitation-per-hour' could do it.