accident survivability in DP motorhome

Labor day weekend 2001 I was going from New York city to Massachusetts in my 2000 Discovery 36T. Traffic was bumper to bumper all the way up and I was in Rhode Island, in traffic we came over a small hill to see everyone slamming on their brakes 1/4 mile up. Car were swerving and looking up the brakes in all lane trying to avoid each other. In a split second I was doing the same. Someone in a pick up truck had lost their bed extender. All the cars were trying not to hit it or other cars. The guy that lost it was coming at a high rate of speed in reverse down the breakdown lane. As he past my door he cut in and hit me. I could not slow fast enough and had to turn in towards the breakdown lane. I think the impact with his truck may have force my tail end over causing me to go off the highway, probably at about 55 mph. Thank god the highway was clear on the side I was running. we went about 3 feet off the road straight towards a large highway sign. I steered to avoid it and we were skidding slightly sideways. I though we would roll for sure. It pulled out of it and recovered. I was able to get back to the road and into a rest area. Cars were still skidding and swerving behind us. I had someone with me in an unsecured chair and go pinned between the chair and a table due to the extreme braking. I called the cops about the whole thing and met a trooper in the rest area. He told us they got calls stating we did roll. I must say the motor home did very well. I have seen photos of them coming apart at the seems, but that time we got lucky.