In the Navy, we were taught there were four types of radiation, Alpha, Beta, Gamma, and Neutron.
We were taught to hold the Alpha in your hand, as it won't penetrate the skin. You put the Beta in your pocket because it won't penetrate your clothing. You eat the gamma, as it won't cause that much damage to your cells. You throw the Neutron away from you, as that is the one that will do the most damage. The first two, an RV would probably be ok, and maybe even stop some of the third. Neutrons are a different story, an RV won't help there.
Either way, I'm not running around wearing a tin-foil hat worrying about it. What will be, will be. There isn't enough truly safe places for all of us, and being I live on flat land on the East coast, any place here would probably become so contaminated with fall-out, it really wouldn't matter where I hide.