Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Motorcoach Flammability Project Final Report: Tire Fires - Passenger Compartment Penetration, Tenability, Mitigation, and Material Performance



Erik L. Johnsson, Jiann C. Yang


Full scale fire experiments were conducted at the National Institute of Standards and Technology (NIST) to investigate tire fire interactions with the passenger compartment of a motorcoach. A burner was designed to imitate the frictional heating of hub and wheel metal caused by failed axle bearings, locked brakes, or dragged blown tires. Two experiments were conducted to determine the mode of penetration of a tire fire into the passenger compartment. For the first experiment, heating to obtain tire ignition was initiated on the exterior of the passenger side tag axle wheel and for the second, on the exterior of the passenger side drive axle wheel. Four experiments were conducted to examine fire-hardening of the motorcoach against tire fire penetration. Methods explored were: replacing flammable external components with metal, covering flammable external components with an intumescent coating, and placing a metal fire-deflector shield above the fender. One experiment with a partially furnished interior investigated tire fire growth within the passenger compartment and the onset of untenable conditions. Measurements of interior and exterior temperatures, interior heat flux, heat release rate, and toxic gases were performed. Also, standard and infrared videos and still photographs were recorded. The experiments showed that the tire fires ignited the plastic fender and glass-reinforced plastic (GRP) exterior side panel (below the windows) upon which the fires spread quickly and penetrated the passenger compartment by breaking the windows. Measurements showed that other potential fire penetration routes (flooring and lavatory) lagged far behind the windows in heating and degradation. Fire-hardening using steel components had the greatest effect, followed by using an intumescent coating. Tenability limits were reached within 11 min after fire penetration throughout the passenger compartment and by 7 min near the fire. Recommendations are made...
Technical Note (NIST TN) - 1705
Report Number


Motorcoach fire, bus fire, tire fire, vehicle fire, window breakage, fire penetration, fire hardening, compartment tenability, transportation fires


Johnsson, E. and Yang, J. (2012), Motorcoach Flammability Project Final Report: Tire Fires - Passenger Compartment Penetration, Tenability, Mitigation, and Material Performance, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 23, 2024)
Created January 27, 2012, Updated February 19, 2017