Reading the police reports and a comment page, seems that there was a 'pilot car' that was the tail end vehicle. Driver of the RV came up the hill and there, on the other side of the hill...the slow moving industrial troupe...including the slow or stopped even, pilot car. Driver of the RV tried to get on the shoulder..they are calling it the slow lane, and I am guessing, that his right front tires hit the soft dirt, that would have pulled him further in and down..and over it went, onto it's roof. The reports suggest that woman was not wearing her seatbelt. Male driver had monir injuries.
The reports keep saying 'Freightliner', so I guess it was a Super C. They are badged as Freightliners.
http://www.albertapolicereport.com/2013/06/07/fatal-motor-home-rollover-on-highway-43/Scroll down for comments.
Gary Haupt