I've been watching a Discovery Canada show last couple of years, "Highway Through ****", about the towing industry - in their case focusing mostly on big rig towing, but it has shown the reality of the danger these guys face...
Here in Alberta there is a rule that whenever you see a first responder with light flashing on the side of the road (tow truck, police, fire, etc...), if you are in the lane immediately adjacent to them you are required to drive half the speed limit, if you drive two lanes over you can drive at the posted speed limit...
I know when I drive on a divided highway and see someone pulled over on the shoulder, if I can I will switch over one lane to give the car extra room... On a single lane highway, I'll just simply give lots of space as I pass by if it's possible given oncoming traffic...