The National Transportation Safety Board today determined that the cause of a fatal bus fire in Texas was insufficient lubrication in the right-side tag axle wheel bearing assembly of the motorcoach resulting in increased temperatures and subsequent failed wheel bearings, which led to ignition of the tire and a catastrophic fire. Global Limo, Inc. failed to conduct proper vehicle maintenance, to do pre-trip inspections, and to complete post-trip driver vehicle inspection reports, thereby allowing the insufficient wheel bearing lubrication to go undetected.
“We will not cease our efforts to push for change to prevent these kinds of accidents from occurring,” said NTSB Chairman Mark V. Rosenker. “ However, unless there is adequate oversight, I am afraid we will continue to see motorcoach accidents that contribute to the unacceptable number of deaths on our nation’s highway.”
On September 23, 2005, a 1998 Motor Coach Industries 54-passenger motorcoach, operated by Global Limo Inc., of Pharr, Texas, was traveling northbound on Interstate 45 near Wilmer, Texas. The motorcoach, en route from Bellaire to Dallas, Texas, as part of the evacuation in anticipation of Hurricane Rita, was carrying 44 assisted living facility residents and nursing staff. A motorist passing by the motorcoach alerted the driver that the right-rear tire hub was glowing red. The driver and nursing staff exited the motorcoach and observed flames emanating from the right-rear wheel well. As they initiated an evacuation, with the assistance from passersby, heavy smoke and fire quickly engulfed the entire vehicle. Twenty-three of the 44 passengers were fatally injured, 2 were seriously injured and 19 received minor injuries. The driver also received minor injuries.
In the Board’s report, it noted that the right rear tire experienced a blowout earlier on the trip. Because the flat tire occurred during the nighttime and in the middle of the hurricane evacuation traffic congestion, the driver and the mechanic who provided roadside assistance would not necessarily have been aware of the tire marks left by a locked wheel indicating a more serious mechanical problem.
Post accident examination of the motorcoach and roadway revealed that the right-side tag axle tire locked. The Board concluded that the tire contacting the pavement was being pulled, not rolling, which caused the blown tire. Once the tire flattened, the weight of the vehicle caused contact between the pavement and wheel rim, wearing a flat spot on the rim. The Safety Board consequently determined that the accident sequence of events including the tire locking began with a lack of lubrication in the right-side tag axle wheel bearing. A wheel bearing unit can fail when it lacks lubrication, which prevents the bearing rollers from rotating freely and leads to friction, which in turn begins to generate heat. This ultimately led to the tire fire.
The Board’s report revealed that Global did not retain vehicle maintenance and repair records as required by Federal Motor Carrier Safety Regulations (FMCSRs). In addition, there was no maintenance program to properly service the vehicle in place. Therefore the Board concluded in the report that the disregard for such a program led to the failure to detect vehicle defects that resulted in a catastrophic fire and loss of life.
Contributing to the accident, the report states, was FMCSA’s ineffective compliance review system, which resulted in inadequate safety oversight of passenger motor carriers. The Board concluded that their current process does not effectively identify unsafe motor carriers and prevent them from operating.
Another contributing factor to the rapid propagation and severity of the fire and subsequent loss of life was the lack of motorcoach fire retardant construction materials adjacent to the wheel well. The report states that the most likely point of initial entry of fire into the motorcoach was burnthrough of the combustible exterior composite materials and through the HVAC ventilation and the windows. The Safety Board concluded that as the fire intensified, it spread up the side of the motorcoach and burnt through the fiberglass sidewall above the wheel wall and through the motorcoach windows, creating an entry path for the smoke and fire into the passenger compartment.
The Board said that the ambulatory condition of many of the passengers played a role in the severity of the accident, and directed that a contributory factor acknowledging that be added to the report.
As a result of its investigation, the NTSB made recommendations to the Federal Motor Carrier Safety Administration, the National Highway Traffic Safety Administration, the Pipeline and Hazardous Materials Safety Administration, the Motor Coach Industries, the United Motorcoach Association and American Bus Association, the Law Enforcement and Emergency Responders Associations. These recommendations include:
- Revising regulations to prohibit a commercial vehicle from operating with wheel seal or other hub lubrication leaks,
- Developing a standard to provide enhanced fire protection of the fuel system in areas of the motorcoaches and buses where the system may be exposed to the effects of a fire; and provide fire hardening of exterior fire-prone materials, such as those areas around wheel walls, to limit the potential for flame spread into motorcoach or bus passenger compartment,
- Developing detection systems to monitor the temperature of wheel well compartments in motorcoaches and buses to provide early warning of malfunctions that could lead to fires,
- Continuing to gather and evaluate information on the causes, frequency and severity of bus and motorcoach fires, and conduct ongoing analysis of the fire data to measure the effectiveness of the fire prevention and mitigation techniques identified and instituted as a result of the Volpe National Transportation Systems Center fire safety analysis study,
- Revising product maintenance manuals to emphasize the importance of wheel bearing lubrication, specifically warning that daily inspection of hub oil levels and wheel seals is vital to prevent wheel bearing failure and that bypassing this requirement is a dangerous practice that can lead to a wheel fire or other serious consequences.
A synopsis of the Board's report, including the probable cause and safety recommendations, is available on the Board's website, www.ntsb.gov, under “Board Meetings.” The Board's full report will be available on the website in several weeks.