"Anybody can see from miles away that the truck is attempting to pass the snowplow."
I live in the area and have driven that same road north from Nipigon, ON. It has loads of turns and hills as it runs through part of the pre-Cambrian Shield, a very old mountain range. It is rare to have a straight flat section of this road 1 mile long, so it's actually hard to see very far ahead. Unfortunately, that means few safe opportunities to pass a slow vehicle, and the result is that too many people get impatient and just go anyway! Snowplows are especially difficult because they are wide and they throw a cloud of snow into the air, making seeing past them really hard. They DO pull off the road at special turn-offs from time to time, and the safest option is to wait for that. But too may people, including truckers, think they can't afford the time to wait.