Our research on 291 passenger vehicles struck by tornadoes while parked outdoors near a house showed that vehicles were rarely tipped over in F2 damage and only 18% were tipped in F3 damage. Our wind tunnel experiments on a sedan and a minivan showed the angle of the wind was important in determining the upset wind speed. A minimum uniform steady wind speed of 50 m/s was required to upset the sedan and 58 m/s to upset the minivan. Gusts, turbulence, and debris could alter these values.
Suggestions will be made for wind speed ranges required to upset common vehicle types for incorporation into the Fujita scale. The impact of wind on a single vehicle is not very informative, so data should be obtained on several vehicles for an F-scale assessment. Whether a severe wind will upset a vehicle will depend on the details of vehicle weight, progressive damage, impacts of debris, wind gusts, direction and duration of wind, exposure, and whether the vehicle was moving when struck. There are similar concerns and debates when assigning F-scales to damage to frame houses and other buildings.