Determining critical wind speeds for overturning two types of ambulances and a large city bus


  • Thomas W. Schmidlin, PhD
  • Barbara O. Hammer, MA
  • Paul S. King, BS
  • L. Scott Miller, PhD
  • Gregory Thumann, MS
  • Helene Wetherington, MA





Two types of ambulances and a city bus were modeled in a wind tunnel for the minimum wind speed required to upset the stationary vehicles. The Type I ambulance was vulnerable to upset with wind speeds of 135 to 150 mph on the vehicle over wind angles of 40° to 145°. The Type II ambulance was vulnerable to upset with wind speeds of 140 to 170 mph over wind angles of 30° to 145°. The 40-passenger city bus was vulnerable to upset with wind speeds of 60 to 75 mph over wind angles of 35° to 145°. These results showed ambulances were more stable in high winds than common passenger vehicles, but the city bus was very vulnerable in high winds. Testing showed that moving ambulances can be driven at low speeds in minimal hurricane-force winds without exceeding the upset wind speeds on the vehicles. This information provides guidance for safe operation of these vehicles during high winds including hurricanes, thunderstorms, and extra-tropical cyclones.

Author Biographies

Thomas W. Schmidlin, PhD

Department of Geography, Kent State University, Kent, Ohio.

Barbara O. Hammer, MA

Department of Geography, Kent State University, Kent, Ohio.

Paul S. King, BS

Boyce Thompson Institute, Cornell University, Ithaca, New York.

L. Scott Miller, PhD

Department of Aerospace Engineering, Wichita State University, Wichita Kansas.

Gregory Thumann, MS

Department of Aerospace Engineering, Wichita, Kansas.

Helene Wetherington, MA

Division of Emergency Management, West Palm Beach, Florida.


Maguire BJ: Ambulance safety in the United States. J Emergency Manage. 2003; 1(1): 15-18.

Urbina E, Wolshon B: National review of hurricane evacuation plans and policies: A comparison and contrast of state practices. Transportation Res Part A: Policy Practice. 2003; 37(19): 257-275.

Schmidlin TW, Hammer B, King P, et al.: Unsafe at any (wind) speed?: Testing the stability of motor vehicles in severe winds. Bull Amer Meteorol Soc. 2002; 83: 1821-1830.

Bettle J, Holloway AGL, Venart JES: A computational study of the aerodynamic forces acting on a tractor-trailer vehicle on a bridge in a cross-wind. J Wind Eng Ind Aerodynamics. 2003; 91: 573-592.

Pinelli JP, Subramanian C, Plamondon M: Wind effects on emergency vehicles. J Wind Eng Ind Aerodynamics. 2004; 92: 663-685.

Angelis W, Drikakis D, Durst F, et al.: Numerical and experimental study of the flow over a two-dimensional car model. J Wind Eng Ind Aerodynamics. 1996; 62: 57-79.

Howell J: The side load distribution on a Rover 800 saloon car under crosswind conditions. J Wind Eng Ind Aerodynamics. 1996; 60: 139-153.

Chen SR, Cai CS: Accident assessment of vehicles on long-span bridges in windy environments. J Wind Eng Ind Aerodynamics. 2004; 92: 991-1024.

Rae WH, Pope A: Low-Speed Wind Tunnel Testing, 2nd ed. New York: John Wiley and Sons, 1984.

Johnson BL, Leigh JE, Moore KA: Three-dimensional force data acquisition and boundary corrections for the Beech Memorial 7 x 10 foot low-speed wind tunnel. Aerodynamics Laboratories Rep. AR93-2, Wichita State University, Wichita, KS 67260, 1993.

Krayer WR, Marshall RD: Gust factors applied to hurricane winds. Bull Amer Meteorol Soc. 1992; 73: 613-617.

Stull, RB: Meteorology Today for Scientists and Engineers. St. Paul: West Publishing Co., 1995.

Beatty K, Miller C, Boissonnade A: Equivalent 10-Meter Wind Speeds in Hurricane Fabian. In Preprints of the 26th Conference on Hurricanes and Tropical Meteorology, Boston: American Meteorological Society, 2004, 613-614.

Stull RB: An Introduction to Boundary Layer Meteorology. Dordrecht: Kluwer Academic Publishers, 1988.




How to Cite

Schmidlin, PhD, T. W., B. O. Hammer, MA, P. S. King, BS, L. S. Miller, PhD, G. Thumann, MS, and H. Wetherington, MA. “Determining Critical Wind Speeds for Overturning Two Types of Ambulances and a Large City Bus”. Journal of Emergency Management, vol. 3, no. 2, Mar. 2005, pp. 21-26, doi:10.5055/jem.2005.0016.