There are so many variables that I'd have to spend a year on research.. But here are some facts.
In a motor home without slideouts anyuting lying loose in the "House" part can come flying and smack you in the back of he head if you stop suddenly.. And even with my main slide (Which protects me) the passanger is exposed. This means if you do not properly pack, it can be more dangerous in one kind of accident.
But then I'd rather get hit in the head by a roll of say Bathroom Tissue, than by the 5th wheel (Seen what happens with the trailer comes through the cab, well, Police photos of it.. Do not wish to see it "live" or the other way)
However if some idiot "T" bones me
If he is driving a Semi, not much difference
If he is driving a car he's going to run UNDER me, I might get shook up a bit, Disoriented for a second or two. But he's a head shorter than when he started (Seen police photos of that too) and like the semi driver who got rear ended (in the photos) I'm ok. Had a heck of a time finding the family of the guy who developed a split personality in that accident, he tried hard to obscure where he lived.. Thankfully I'm better at research than he was at hiding. (I was a Police Dispatcher).
