Federal requirements allow the use of untreated polyurethane foam cushioning used in bus seating, which fire safety professionals often describe as “solidified gasoline.”  iStock-dogayusufdokdok

Bus fires are an all too common occurrence within public transportation. Tires blow and ignite from the friction, faulty brakes spark a blaze, engines erupt from a multitude of mechanical and electrical issues, and unexplained combustions are a continuous plague to transit authority fleets. As expected, accidents add further opportunities for destructive and dangerous fires. With these risks, one should assume the highest precaution is mandatory to keep the interior of the vehicle as flame-resistant as possible, to give passengers the most valuable commodity in the event of an emergency — time to evacuate.

Quite the opposite is true, however. In bus interiors, the key combustible components are seating materials, and the federal regulations for seat cushioning and covers are grossly insufficient and outdated for fire safety. In fact, cushioning materials currently used in buses ignite easily and spread fire rapidly. Requirements allow the use of untreated polyurethane foam cushioning, which fire safety professionals often describe as “solidified gasoline.”

To help avoid potential disaster, it is essential to demand that, at least, FTA Docket 90-A be required as the fire-performance criteria for all transit buses, and at minimum, to require it for the seat cushion and upholstery components within the vehicle.

The only fire test that any material in the interior of a highway vehicle, including buses, must meet is the fire performance required by the Federal Motor Vehicle Standard No. 302 (FMVSS 302). FMVSS 302 is administered by the National Highway Traffic Safety Administration (NHTSA), which regulates safety of all highway vehicles. This standard applies to all materials used in the interior compartment of a vehicle, including such components as seat cushions, upholstery, seat belts, headlining, armrests, trim panels, compartment shelves, floor coverings, sun visors, and airbags. It has been shown that almost any material will comply with the minimal horizontal flame spread that FMVSS 302 requires. (49 CFR § 571.302)

In buses with cushioned seats, the upholstery and foam represent the largest fuel load within the interior compartment. Typically, seat cushioning with minimum compliance to FMVSS 302 defaults to use of a traditional untreated polyurethane foam, or urethane foam. When exposed to even minor ignition sources, such as a match or lighter, this polyurethane cushioning is likely to ignite easily, burn profusely, melt, drip, and rapidly ignite the surrounding materials, while emitting large volumes of toxic smoke.

The dangers of untreated polyurethane foam within vehicles have been well known since the late 1970s.

The dangers of untreated polyurethane foam within vehicles have been well known since the late 1970s. In an article from the Los Angeles Times in 1979, “an official of the National Highway Traffic Safety Administration says, ‘Polyurethane shouldn’t be used in public transportation. It’s extremely noxious when it burns… it is one thing for vehicle occupants to evacuate a burning automobile, and yet another for a bus full of panic-stricken passengers to escape from a burning bus, especially if it’s lying on its side.’” (Gillette,1979)

The state of motorcoach, public transit regulations
FMVSS 302 was generated in the 1960s from the NHTSA as a small-scale regulatory fire test with a very miniscule ignition source, intended for cars. During that era, the concern was to help solve the problem of smoldering ignition caused by cigarettes. When this approach was developed, it was assumed that cars can reach a stop rapidly and the passengers can evacuate immediately — something that has since been proven to be incorrect. Also, the use of combustible materials in highway vehicles has been increasing over time. Today, while cigarettes are not a major concern for buses, it is clear the highly combustible materials allowed for seat cushioning and covers can significantly increase the risk of rapidly spreading fire and toxic smoke with passengers still inside. (Hirschler, 2006)

On April 10, 2014, in Northern California, a delivery truck crossed into oncoming traffic and slammed into a high school charter bus causing a fire that left 10 people dead and 39 injured. The massive impact immediately ignited a fire, blocking the exit. "I looked forward to the bus, and I just see fire," one student said, "just fire, a ball of fire." There was only one other door, for handicap access, which was locked and could only be opened by the bus driver, who was killed in the crash. Survivors kicked out windows in the back of the bus to escape, pouring out, three people at a time, to a seven-foot drop. Seven of the fire fatalities were found to be a result of smoke asphyxiation, as a result of the fire growing. (Cocoa, 2014)

One year later, the National Transportation Safety Board (NTSB) voted to urge the development of fire safety regulations to add fire-resistant materials into buses, to increase the chances of survival following crashes. Members of the NTSB reprimanded NHTSA for failing to act on recommendations made over three decades ago to improve flame-resistance standards. The report states “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-resistance material standards more appropriate for large commercial vehicles with increased passenger capacity.” The NTSB Chairman at the time, Christopher Hart, said the case exposed “double standards in regulations protecting motorcoach passengers,” he said, “the 302 standard has not been updated; however, other modes of transportation like rail and aviation, have made improvements to the standards.” His argument is correct, while other public transportations have increased their fire safety regulations, bus requirements still cling to the inadequate FMVSS 302 standard as the sole and minimum fire-performance criteria. However, NHTSA did not act (United Motorcoach Association, 2015).

FTA regulation
The safety of mass transportation in the U.S. is regulated by the Federal Transit Administration (FTA), but it does not issue requirements related to fire safety. In the 1970s it issued guidelines, to be applied voluntarily, for the fire safety of buses and trains. This means that the FTA already has the guidelines necessary for an equivalent overhaul for the bus industry.

Docket 90-A is the FTA’s recommended fire safety criteria for transit bus and vans.

  • These recommendations include using a flame spread test (ASTM D3675) for assessing cushioning materials and a smoke test (ASTM E662) for minimizing smoke release within the interior of the bus. (United Motorcoach Association, 2015).
  • Currently, the only way these recommendations are utilized is through the discretion of the purchasing transit authority, to include as the seating standard within their vehicle solicitations.
  • Without specifying this necessary and increased fire protection, the requirements revert back to the inadequate FMVSS 302 standard, which does not comply with FTA Docket 90-A.

Passenger railcars
In the early 2000s, the Federal Railroad Administration (FRA) mandated for a massive overhaul of requirements for fire-resistant materials for passenger railcars within their jurisdiction and they are based on previous DOT guidelines similar to current Docket 90-A criteria.

Federal Regulation 49 CFR Part 238 Appendix B requires that all combustible materials inside railcars must meet certain fire tests.

  • For example, seat-cushioning materials must meet criteria based on ASTM D3675 for flame spread and ASTM E662 for smoke generation.
  • The certification to these stringent tests has proven to be adequate to prevent rapid fires and intense smoke generation, as well as to reduce the likelihood of flames to overtake the railcar interior.

People with disabilities
It is important to note that public transportation is frequently used to transport passengers with mobility constraints such as the elderly or disabled. According to the Bureau of Transportation, people aged 18 to 64 with disabilities utilize local transit for a greater number of trips than people without disabilities. As a result, many riders within public buses are subject to certain disadvantages in the event of an emergency, and at the sole mercy of good Samaritans to help.

This past July, a bus from the Milwaukee County Transit System burst into flames. Alerted by passersby of the fire in the rear of the bus, the experienced driver pulled the bus to a stop, and instructed passengers to evacuate, leaving a wheelchair bound man still strapped in. With no time to put the ramp down, the driver immediately went towards the fire, unhooked the wheelchair with the assistance of other passengers, picked it up and moved the man to a safe distance. "Just carried me and the chair off the bus," the passenger said. "Without them, who knows what would have happened." (CBS 58 Newsroom)

Changes are necessary
For reasons unbeknownst to the NTSB, NHTSA has yet to make any moves to adopt the increased fire-resistance recommendations of the FTA Docket 90-A. Currently, even with the widespread knowledge of the potential fire hazards resulting from the sole reliance on FMVSS 302, many insufficient vehicle specifications continue to put passengers, operators, and equipment at risk. To help avoid potential disaster, it is essential to demand that, at least, FTA Docket 90-A be required as the fire-performance criteria for all transit buses, and at minimum, to require it for the seat cushion and upholstery components within the vehicle.

Alicia Dixon is the Sr. Marketing Coordinator for Chestnut Ridge Foam, a manufacturer of fire-resistant and specialty foam products.

49 CFR § 571.302 - Standard No. 302; “Flammability of interior materials” Retrieved from https://www.law.cornell.edu/cfr/text/49/571.302

Gillette, Robert (January 23, 1979) Los Angeles Times ”Urethane Still Used Widely in Transit” Page 6

Hirschler, Marcelo New NFPA Guide on Fire Safety of Road Vehicles
SAE International, 2006

Cocoa, Christina (April 10, 2014) “10 Killed in Bus Crash; Southern California High School Students Aboard” NBC Los Angeles 4. Retrieved from https://www.nbclosangeles.com/news/local/tour-bus-fedex-crash-northern-california-los-angeles-students-254835921.html

United Motorcoach Association (August 15, 2015) “NTSB calls for new coach regulations in wake of fatal crash” Bus & Motorcoach News

Federal Registrar Department of Transportation Part IX, Vol. 58, No. 201
October 19, 1993

CBS 58 Newsroom (July 15, 2019) “MCTS bus catches fire near 76th
About the author
Alicia Dixon

Alicia Dixon

Sr. Marketing Coordinator, Chestnut Ridge Foam Inc.

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