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Motorcoach 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 right side tag axle wheel and for the second, on the exterior of the right side drive axle wheel. Three experiments were conducted to examine fire-hardening of the motorcoach against tire fire penetration. The methods explored were: (1) replacing combustible external components with metal, (2) covering combustible external components with an intumescent coating, and (3) placing a metal fire-deflector shield above the fender. A final 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, toxic gases, and visibility 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. Fire- hardening using steel components had the greatest effect. Tenability limits were reached within 11 min after fire penetration throughout the passenger compartment and by 7 min near the fire. In addition to the full-scale motorcoach experiments, the flammability performance of four interior combustible motorcoach components was tested beyond the current requirements.
Proceedings Title
Fire in Vehicles 2012
Conference Dates
September 27-28, 2012
Conference Location
Chicago, IL


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 Tire Fires – Passenger Compartment Penetration, Tenability, Mitigation, and Material Performance, Fire in Vehicles 2012, Chicago, IL, [online], (Accessed April 19, 2024)
Created September 27, 2012, Updated February 19, 2017