I think looking at number of people killed in car accidents versus tornadoes is the wrong way of seeing it.
The question should be "how are the odds different between two people in direct line of a tornado if one person sits in their RV to wait it out and the other person goes to recommended shelter"?
Out here in California, I don't really worry about tornadoes. But I do know what precautions to take in an earthquake. Not because I fear dying in an earthquake but because I don't want to die in an earthquake.