Taking Shelter: Estimating the Safety Benefits of Tornado Safe Rooms

Abstract

Over the past several decades, engineers have made significant progress in the design and construction of structures able to withstand tornadic winds and debris. The aftermath of the 3 May 1999 F5 tornado in Moore, Oklahoma, highlighted the modest market penetration of tornado shelters in metropolitan areas. The authors use historical data from Oklahoma to estimate the potential casualties that tornado shelters could prevent and calculate that the cost per fatality avoided in single-family homes is $29 million while the cost per fatality avoided for mobile homes is $2.6 million. The estimates are sensitive to the proportion of strong (F3 or stronger) tornadoes and the choice of an interest rate for present-value calculations. If the F-scale distribution of Oklahoma tornadoes resembled a reported national frequency distribution and fatalities per category storm are held constant, the permanent home cost per fatality avoided triples to $88 million.