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From:
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NTSB
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To:
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NHTSA
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Date:
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7/16/2019
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Response:
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Reiterated in the Highway Accident Report “School Bus Run-Off-Road and Fire Oakland, Iowa, December 12, 2017” Report number HAR-19-01, adopted June 18, 2019 and published July 16, 2019.
The National Transportation Safety Board reiterates safety recommendation H-15-12 in section 2.4.4 of this report.
2.4.4 Safety Recommendations
FMVSS 302 applies to all vehicles, regardless of the number of passengers and the time needed for egress in a fire. However, the FMVSS 302 performance tests cannot predict a material’s fire performance (combustion behavior) when exposed to a large ignition source, such as a fire propagating from the engine compartment. To increase the likelihood of passenger survivability and delay flashovers (fire rapidly spreading across a gap), requirements are needed for the flammability and smoke-emitting properties of the materials used in high-occupancy commercial passenger vehicles, including school buses.
The NTSB (2015) has found that the current criteria for testing the flammability and smoke emissions of the materials used in the interiors of motor vehicles are inadequate, and that significant upgrades of FMVSS 302 are needed to improve the safety of today’s high-occupancy commercial passenger vehicles, including school buses. The standard should establish a more stringent set of flammability requirements to reduce the propagation of passenger compartment fires and permit longer evacuation times. As a result of previous investigations, the NTSB has issued recommendations aimed at identifying a means of increasing postcrash occupant survivability, such as the use of fire-retardant materials that can extend the time available for escaping a vehicle. In aviation, for example, NTSB recommendations have led to improvements in postcrash occupant protection (NTSB 2001).
FMVSS 302 is outdated and less stringent than the flammability standards applied in other modes of transportation under US Department of Transportation oversight, such as aviation and rail (NIST 2012). Just as in airplane and passenger train fires, the danger to school bus passengers is not limited to exposure to flames. The side effects of a fire, such as inhaling products of combustion, can be equally deadly. In its report on the motorcoach fire in Orland, California, the NTSB concluded that FMVSS 302 does not adequately account for modern vehicle interior components or conditions experienced in real-world vehicle fires, nor does it include specific fire-resistant material standards appropriate for large commercial vehicles (NTSB 2015). As a result, the NTSB made the following recommendation to NHTSA:
Revise FMVSS 302 to adopt the more rigorous performance standards for interior flammability and smoke emissions characteristics already in use throughout the US Department of Transportation for commercial aviation and rail passenger transportation. (H-15-12)
Safety Recommendation H-15-12 is currently in “Open—Acceptable Response” status. NHTSA reported to the NTSB in December 2015 that it “was evaluating standards already in use in other transportation modes, such as commercial aviation and rail passenger transportation,” and that it intended to “initiate a new research project to inform our decision to upgrade FMVSS No. 302. Components of that research will include vehicle interior material flammability and smoke emissions characteristics.” Then in 2017, NHTSA publicly announced that a research effort titled Test Procedures for Evaluating Flammability of Interior Materials was under way and that final results were expected to be published in June 2018. The NHTSA announcement included a work plan to also consider supplementary methods specific to school buses. No results have yet been published. The NTSB concludes that the Oakland fire, along with other school bus fires reported nationally and as shown in school bus fire demonstrations, illustrates that once a school bus compartment is breached (even when an exterior fire enters the bus), a fire spreads quickly, and smoke, toxic gases, and heat make the interior untenable for occupancy.
As part of its 2017 research effort, NHTSA contracted with SwRI to perform testing. SwRI presented its findings to date at the SAE International Government Industry Meeting in Washington, DC, in April 2019.94 SwRI reported that it had used the microscale combustion calorimeter (MCC) to test 29 materials used in motor vehicle interiors, motorcoach interiors, and school bus seats; thin materials were also included to test at least one that would fail FMVSS 302 (manila file folder cardboard).95 The materials were tested using both FMVSS 302 and ASTM standard D7309.
SwRI reported that its statistical analysis “showed that failure in the FMVSS 302 test can be predicted based on two MCC parameters and specimen thickness and density.” SwRI had established an equivalent MCC pass/fail criteria along with an alternative criterion, independent of thickness. SwRI stated that work is in progress to address challenges with the MCC method and to develop a laboratory procedure. SwRI is expected to present additional information at the Interflam conference in July 2019.97 The NTSB is closely following SwRI’s work as well as NHTSA’s progress with Safety Recommendation H-15-12, and reiterates Safety Recommendation H-15-12 to NHTSA.
Engine fire suppression systems or mitigation through fire-resistant materials offers large safety benefits in helping prevent unnecessary death or injury from bus fires, as the NTSB has addressed in previous reports and recommendations. Even without a fire suppression system, had the Oakland school bus been equipped with a complete firewall or with fire-resistant materials between the engine and the passenger compartment, the spread of fire and smoke into the bus’s interior would have been reduced or slowed. Exposure of the occupants to smoke and heated gas would have lessened, and the time available to evacuate the bus would have increased. As a result, the two fatalities might have been prevented.
Therefore, the NTSB recommends that NHTSA require all new school buses to be equipped with fire suppression systems that at a minimum address engine fires. The NTSB further recommends that the US Department of Transportation require in-service school buses to be equipped with fire suppression systems that at a minimum address engine fires. Firewalls should act as complete protective barriers in the event of a fire. The NTSB therefore recommends that NHTSA develop standards for newly manufactured school buses, especially those with engines that extend beyond the firewall, to ensure that no hazardous quantity of gas or flame can pass through the firewall from the engine compartment to the passenger compartment.
It will take time to enact FMVSS regulations requiring fire suppression systems on school buses and enhancements to barriers between passenger compartments and the engines. But school bus manufacturers can take action on these safety improvements now. Therefore, the NTSB recommends that as standard equipment on all newly manufactured school buses, Blue Bird Corporation, Collins Industries, Inc., IC Bus, Starcraft Bus, Thomas Built Buses, Trans Tech, and Van-Con, Inc., install fire suppression systems that at a minimum address engine fires.
To achieve a higher level of firewall protection, school bus manufacturers need to prevent the spread of fire through sealed openings that have no fire resistance, as well as make fireproof school buses that have an engine that extends through the firewall into the passenger compartment. Any opening or penetration of the engine firewall could be sealed with close-fitting, fireproof grommets or bushings, or be coated with or use fire-resistant materials. The NTSB therefore recommends that Blue Bird Corporation, Collins Industries, Inc., IC Bus, Starcraft Bus, Thomas Built Buses, Trans Tech, and Van-Con, Inc., ensure that, for any opening or penetration of the engine firewall, no hazardous quantity of gas or flame can pass through the firewall from the engine compartment to the passenger compartment in newly manufactured school buses.
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