resistance requirements. The FRA's letter also stated that it would have to obtain more information to provide a basis before determining a research approach on this issue due to the competing expectations for railcar window performance. The letter further stated that the FRA expected this research to provide performance data on window retention and passenger containment; evaluate existing and potential designs and design methodologies for window systems; and investigate practical testing metrics and methodologies to assess and quantify containment capabilities. Once this research is complete, FRA can assess the influence of design methodologies that enhance containment capabilities while preserving the ability of window systems to provide required emergency egress and rescue access without compromising other safety purposes. The expected completion date for the research is October 2016. The FRA said it will then be able to determine proposed regulatory changes that are reasonable and practical. Safety Recommendation R-14-74 is currently classified "Open—Acceptable Response."
The NTSB recognizes that developing a performance standard and incorporating it into the federal regulations will require research and time. Nonetheless, the Philadelphia accident has again demonstrated the necessity for this standard to protect occupants during accidents; therefore, the NTSB reiterates recommendation R-14-74. [Recommendation Reiteration]
1.8.3 Occupant Protection in Derailment Scenarios
Among the 46 people who were seriously injured in this accident, the majority sustained torso or chest injuries. Twenty-four of those who were seriously injured sustained 68 chest injuries at Abbreviated Injury Scale (AIS) level 2 or higher.[1] (The number of injuries exceeds the number of people because one individual can sustain multiple chest injuries.) This included flail chests (in which a series of ribs are fractured in multiple places resulting in impairment of respiratory function), pulmonary contusions, people with multiple rib fractures, and a fractured sternum. There were fewer head and neck injuries: four people sustained fractured cervical vertebrae each coded with an AIS score of 2; there was one head injury with an AIS score of 3, and one person had a cervical fracture with a spinal cord injury with an AIS score of 5.
The NTSB considered the possible causes for this number of serious torso injuries. In a collision that results in the railcars remaining upright and in line, the occupants would likely strike the seat back in front of them and remain close to their seating area.[2] This is known as "compartmentalization." Compartmentalization, although not required, has been one strategy to protect occupants in railroad accidents by restricting their movement and preventing them from being thrown from their seats in the car. In the preamble to its final rule promulgating the Passenger Equipment Safety Standards currently codified at 49 CFR Part 238, the FRA noted that based on previous research, interior passenger protection requirements for Tier I and II passenger cars rely on compartmentalization as a passenger protection strategy.[3] As currently
- ↑ The Abbreviated Injury Scale (AIS) uses a 1–6 scale to score injuries for the likelihood that the injury is life-threatening. On this scale, 1 is a minor injury (contusion, superficial laceration), and 6 is fatal. AIS 2005 Update 2008. Association for the Advancement of Automotive Medicine. Barrington, IL 2008.
- ↑ This assumes that the seat back is high enough to restrict forward motion. For further details about seat testing and compartmentalization, see Commuter Rail Seat Testing and Analysis DOT/FRA/ORD-01-06.
- ↑ Federal Register 64, no. 91 (May 12, 1999): 25540.
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