Very often on TV news and shows about weather advice is given about what best to do if you are caught in the path of a tornado. Almost always included is instructions if you're driving. Obviously if a suitable shelter, such as a building is accessible, that would be your best option. If proper shelter is not available they usually tell you to drive out of its path at right angles if possible, but if you can't get away people are advised to get out of their car and lie in a ditch. Here's one such example from The Weather Channel's website:
If you're stuck in heavy traffic and there's nowhere for you to to go, it's time to duck and cover in a ditch or low spot. In that case, NOAA recommends getting as far away from your car as possible.
Although not specifically designed for tornado survival, today's cars are designed to withstand impacts from several different angles and rollovers. They have numerous safety features such as seatbelts, airbags, safety glass and roll cages.
Although it is possible in a strong tornado to be pulled airborne and tossed around, most people killed in tornadoes are struck by flying or falling debris. It seems that getting out of your car is the last thing you would want to do. Rather than being seatbelted into the relative safety of a steel cage you would be exposed to any flying debris, possibly including the vehicle you just got out of. As a matter of fact, one expert stated that persons in mobile homes who didn't have more adequate shelter would be safer leaving the home and getting in their car.
The only site I could find that seemed to recommend staying in your vehicle is NOAA's Storm Prediction Center:
Stay in the car with the seat belt on. Put your head down below the windows; cover your head with your hands and a blanket, coat, or other cushion if possible.
But in the very next sentence they say
If you can safely get noticeably lower than the level of the roadway,leave your car and lie in that area, covering your head with your hands.
Although I consider NOAA and The Weather Channel to be experts at predicting and analyzing tornadoes, I have doubts about their advice in this instance. Is there any solid evidence that shows that you would ever be safer outside your vehicle than inside it?