The Stability of Passenger Vehicles at Tornado Wind Intensities of the (Enhanced) Fujita Scale

Abstract

wo independent datasets (total n = 959) of tornado-stricken passenger vehicles collected from 12 tornado events over a 15-yr time span are combined and tested to determine whether vehicle movement and/or upset are consistent at various wind speed intensities. Impacted vehicles are classified into three categories of upset motions (no movement, lateral shifting, rolling and lofting motions) for each wind intensity category of the Fujita and Enhanced Fujita scales. Vehicles observed by Schmidlin exposed to F1 and F2 winds are statistically assessed to determine if upset distribution values are consistent with those assessed by Marshall at these respective wind speeds; this same approach is subsequently conducted for vehicles at F3/EF3 and F4/EF4 winds. No statistical differences are found between the two sets of field survey data, which are therefore considered to be of the same population. Passenger vehicles are currently not utilized as damage indicators for rating tornado wind intensities, although the results of this study suggest that only 10% of vehicles are typically shifted at EF0 wind speeds, 36% are displaced at EF1 and EF2 winds (5% are rolled or lofted), 63% are displaced at EF3 and EF4 winds (15% are rolled and lofted), and all vehicles exhibit some form of movement or upset at the EF5 wind speed. The results of this study may potentially serve as a basis for providing better tornado safety protocols, designing safer vehicles and infrastructure, and estimating tornado wind speeds where few EF-scale damage indicators are available.