• Mary Pat McKay, Kristin Poland, and Thomas H Barth.
• a Office of Research and Engineering, National Transportation Safety Board , Washington , DC .
• Traffic Inj Prev. 2018 Jan 1; 19 (sup2): S162-S164.

ObjectiveThe objective of this study was to examine the medical conditions of 2 commercial drivers and the effects of physical barriers to occupant egress in a crash involving a tractor trailer and a motorcoach in order to assess and identify the factors that caused the crash and had a significant effect on occupant extrication.MethodsPhysical evidence from the scene, video evidence, commercial driver information, phone records, toxicology findings, autopsy results, and personal medical information were reviewed.ResultsOn October 23, 2016, at 5:16 a.m., a motorcoach carrying a driver and 42 passengers struck the rear of a stopped semitrailer occupied by its driver in the center-right lane of Interstate 10 at highway speed outside Palm Springs, California. The motorcoach driver and 12 passengers died; 11 passengers were seriously injured. All traffic had been stopped on I-10 early that morning to allow electrical lines to be strung over the highway. Security camera footage showed that the truck arrived at the end of a traffic queue 2 min before traffic flow resumed. Physical evidence indicated that the truck's parking brake was still engaged at the time of the collision about 2 min later. The truck driver had a body mass index (BMI) between 45.6 and 50 kg/m2, which placed him at very high risk of moderate to severe obstructive sleep apnea; he also inaccurately recalled that he had been stopped for 20-25 min and had placed the vehicle in gear just before the collision. The motorcoach driver was on the return leg of an overnight trip to a casino. Based on his phone records, known driving time, and security camera footage, at the time of the collision he had had 4 h of sleep opportunity in the preceding 35 h. There was no evidence that the motorcoach driver attempted any evasive action before the collision. In addition, postmortem testing revealed a hemoglobin A1C of 11.4%, indicating poorly controlled diabetes; this was apparently undiagnosed prior to the crash. The motorcoach was equipped with a single loading door at the front of the vehicle; it was rendered inoperable by the collision. Emergency egress was initially carried out through the emergency exit windows, but they repeatedly swung shut, impeding passengers' efforts to exit. Emergency responders eventually cut open the bus wall to create a larger means of egress. Overall, it took almost 3 h to extricate the occupants from the vehicle.ConclusionsThe National Transportation Safety Board (NTSB) determined that the probable cause of the accident was the truck driver's falling asleep, most likely due to undiagnosed moderate-to-severe obstructive sleep apnea, and the motorcoach driver's failure to identify the stopped truck as a hazard requiring evasive action, most likely as the result of fatigue. Additional easy-to-use emergency exits would have decreased the time to extricate the occupants.

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