Rollover-Activated Curtain Airbags—
`Past, Present, and Future
`
`Jennifer K. Jousma, Esq.
`
`Ford Motor Company
`
`One American Road, Suite 430-A3
`Dearborn, MI 48126
`(313) 845-8780
`jjousma@ford.com
`
`Stacy M. Imler, Ph.D., P.E.
`
`Exponent, Inc.
`
`3350 Peachtree Road NE, Suite 1125
`Atlanta, GA 30326
`(678) 412-4802
`simler@exponent.com
`
`

`

`Jennifer K. Jousma is an attorney with the Office of General Counsel of Ford Motor
`Company in Dearborn, Michigan. Her practice concentrates on product liability
`litigation, including litigation involving allegations of lack of rollover-activated
`curtains and class actions.
`Stacy M. Imler is a managing engineer in Exponent’s biomechanics practice in
`Atlanta, Georgia. Dr. Imler addresses issues related to the biomechanics of human
`injury, with expertise in the areas of occupant kinematics, human tolerance, and
`rigid body dynamics. She has significant research efforts in the areas of rollover-
`activated side curtain airbags as well as analysis of field-accident data to evaluate
`injury risk. Dr. Imler’s experience and knowledge allow her to assist clients in
`evaluations of injury mechanisms, assessments of the effects of alternative designs
`on injury outcome, and risk of injury given specific accident parameters.
`
`

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`Rollover-Activated Curtain Airbags—
`Past, Present, and Future
`
`Table of Contents
`I. Introduction ...............................................................................................................................................251
`II. Rollover-Activated Curtain Airbags .........................................................................................................251
`
`IPR 2016-01790
`American Vehicular Sciences
`Exhibit 2027
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`Rollover-Activated Curtain Airbags—Past, Present, and Future
`
`
`
`I. Introduction
`Rollover-activated curtain airbags were first available in late 2002 model year vehicles. Efforts to
`develop, introduce, and implement this technology in the passenger vehicle fleet was driven by vehicle and
`component part manufacturers, and, until recently, proceeded in the absence of applicable Federal regulation.
`This safety technology was implemented into production vehicles only after extensive development and test-
`ing performed by component and vehicle manufacturers. Implementation of this technology into the vehicle
`fleet has followed a phase-in approach for multiple reasons, including technological challenges, still-limited
`field performance data, and the potential for unintended consequences. Over the subsequent decade, mar-
`ket implementation of this technology has increased, and bag configuration, coverage, and energy capacity
`have evolved. Further advances in the technology are being implemented to meet performance criteria to sat-
`isfy the 2017 compliance date set forth in Federal Motor Vehicle Safety Standard (FMVSS) No. 226, “Ejection
`Mitigation”. The speakers will discuss the challenges in litigation surrounding this technology, as well as the
`research and field performance as they relate to mitigation of catastrophic injury.
`
`
`
`II. Rollover-Activated Curtain Airbags
`The first rollover-activated side curtain airbags were offered by Ford Motor Company in their 2002
`1/2 model year Ford Explorer/Mercury Mountaineer 4-door sport utility vehicles, manufactured after March
`4, 2002. The purpose of this technology, referred to as the Safety Canopy in Ford vehicles, was to provide
`incremental benefit to belted occupants in rollover crashes. Implementation of this technology into produc-
`tion vehicles involves rigorous developmental and testing work to design, develop, and test the overall system
`which includes the curtain airbag, seat belt pretensioners, restraint control module, and platform-specific
`algorithms for sensing and deployment, all integrated
`within a specific vehicle platform. Since the intro-
`duction of rollover-activated curtain airbags in 2002,
`vehicle manufacturers have continued to incorporate
`this technology into their vehicle fleet at a steady rate
`with a sharp increase in market insertion starting in
`the 2010 model year as shown in Figure 1 (NHTSA,
`2014).
`
`Initial efforts in the development of rollover-
`activated curtain airbags were directed at providing
`incremental head protection through cushioning, as
`well as a level of supplemental containment through
`reduced portal size. These objectives were balanced
`against the goal of minimizing injury potential associ-
`ated with deployment and occupant interaction with
`the device (e.g., the system must “do no harm”). The
`resulting systems have evolved and will continue to
`evolve in response to regulatory efforts, but have finite
`coverage, finite energy capacity, and finite head cush-
`ioning capacity. These concepts are demonstrated in
`
`Figure 1: Percentage of vehicles with side airbags,
`including rollover-activated curtain airbags, by
`model year (NHTSA, 2014).
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`the National Highway Traffic Safety Administration’s (NHTSA’s) guided impactor testing of production systems,
`wherein it has been demonstrated that the greatest curtain retentive capacity occurs in the regions where the
`curtain is supported by vehicle structures (e.g., greatest retention at the upper rear aspect for the front window
`positions). The lowest retentive capacity occurs at the unsupported perimeter of the curtain airbags or in areas of
`limited coverage. In the region of lower retentive capacity, tests have demonstrated motion of the guided impac-
`tor well beyond the glass plane as well as past the boundaries of the curtains, resulting in ejection of the impac-
`tor. More generally, this testing demonstrates that forceful occupant loading to an inflated rollover curtain airbag
`results in movement of the curtain airbag into and through the window plane and can result in occupant ejec-
`tion. Additional research has demonstrated that curtain airbags do not prevent occupants from contacting the
`interior roof panel, and cannot preclude occupant motion beyond the window plane, occupant head-to-roof inte-
`rior roof contact, or occupant ejection through a roof portal (e.g., moonroof).
`Rollover curtains are passive supplemental restraint systems to seat belt use. Analysis of field acci-
`dent data demonstrates that seat belt use is highly effective in the prevention of occupant ejection and in
`the reduction of serious and fatal injury in rollovers (Malliaris et al., 1996; Moore et al., 2005). For example,
`Malliaris and Digges (1999) found that 98.8% of belted pickup rollover occupants did not sustain serious or
`greater injury. Further, they reported that serious and greater injury rates of 1.4% to 3.1% for belted passenger
`vehicle occupants in rollover crashes.
`Published research examining field accident data has shown that an occupant’s injury risk cannot
`be reduced to zero through implementation of a particular safety countermeasure, particularly for occu-
`pants involved in severe crashes. Analysis of initial field accident data which includes vehicles equipped with
`rollover-activated curtain airbags demonstrates estimates of fatality reduction of approximately 20% to 40%
`(Padmanaban and Fitzgerald, 2012; NHTSA, 2014). Examination of the distribution of rollovers shows that
`the average rollover crash in the field involves less than 2 quarter revolutions (Gloeckner et al., 2007), and it is
`well established that occupant injury potential increases with increases in the number of quarter revolutions
`(Moore et al., 2005; Eigen, 2003). Accordingly, to estimate curtain efficacy in multiple roll events, the NHTSA
`specifically incorporated this relationship with recognition of reduced rollover curtain airbag efficacy with
`increased exposure for belted, partially ejected occupants (NHTSA FRIA, 2011).
`Field accidents contain examples of fatal injury as a result of partial ejection even in the presence of
`a deployed rollover-activated curtain airbag. One such accident is reported within the Special Crash Investiga-
`tion Program of NHTSA (Calspan, 2010) and involves a 2003 Lincoln Aviator equipped with rollover-activated
`curtain airbags and laminated side windows in the first row of seating. During the rollover of at least eight
`quarter revolutions, the curtain airbags deployed, and the restrained driver was partially ejected through the
`left front window opening, sustaining fatal injury. Within the Technical Report related to this investigation,
`contact evidence was present on the outboard surface of the deployed curtain airbag. It was concluded that
`the driver’s “head traveled through the glazing opening and was captured between the ground and the mid-
`point of the left roof side rail.” Examples such as this as well as those encountered in litigation, demonstrate
`that for belted occupants, the presence of a deployed rollover-activated curtain airbag cannot preclude partial
`ejection or fatal injury.
`In addition to ejection related injuries, research examining the effects on occupant kinematics and
`occupant loading in the presence of rollover-activated curtain airbags has been performed in the context of
`catastrophic neck injuries, also referred to as “diving” injuries, sustained during rollover crashes as a result of
`torso augmentation at vehicle-to-ground impact. It has been shown in spin testing as well as in full-scale roll-
`over testing that the presence of a rollover-activated curtain airbag does not prevent the up-and-out motion of
`a belted dummy. Further, the presence of a rollover-activated curtain airbag does not prevent the head from
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`coming into contact or close proximity to the interior of the roof and does not prevent the head-neck-torso
`alignment needed for “diving” injuries (Heller et al., 2015; Newberry et al., 2014). Testing utilizing a rollover
`component system demonstrated that the use of pretensioners and rollover-activated curtain airbags did not
`preclude head contact with the roof and had a limited effect on the overall magnitudes of the dummy neck
`loading at roof-to-ground impacts (McCoy, 2010). These tests demonstrate the potential for occupants to sus-
`tain catastrophic neck injury even in the presence of a deployed rollover-activated curtain airbag.
`As with considerations for implementation of all safety countermeasures, the incremental benefits in
`safety provided by rollover-activated curtain airbags need to be balanced with the goal of minimizing occupant
`injury potential related to deployment (i.e., the safety countermeasure should “do no harm”). As supported by
`field accident data, there are limitations to the efficacy of rollover curtain technologies, particularly in high sever-
`ity rollover crashes. It is noteworthy that the initial analysis estimating a 20% to 40% reduction in fatal injuries
`with rollover-activated curtain airbags is applied to the 2% to 3% of the belted occupants sustaining serious to
`fatal injury in rollovers, thus demonstrating that this incremental benefit is applicable to a fraction of occupants
`in rollover crashes. Further, the design and performance goals need to be balanced with the inherent risks, to
`result in a system which will increase occupant safety. However the resulting system cannot mitigate all serious
`injuries. For a particular rollover crash, the occupant injury outcome related to the performance of the rollover
`curtain technology is dependent on the vehicle-, occupant-, and crash-specific parameters.
`FMVSS No. 226: Ejection Mitigation
`On January 19, 2011, nearly a decade after vehicle manufacturers first introduced rollover-activated
`curtain airbags into production vehicles, the NHTSA published a Final Rule pertaining to ejection mitigation
`(Federal Register / Vol. 76, No. 12). Federal Motor Vehicle Safety Standard (FMVSS) No. 226, “Ejection Mitiga-
`tion”, was established “to reduce the partial and complete ejection of vehicle occupants through side windows
`in crashes, particularly rollover crashes.” As detailed in the Final Rule, ejection mitigation countermeasures
`are required to limit the outboard displacement of a projected headform to 100 mm (3.9 in) beyond the inside
`surface of the window glazing of the portal. It is anticipated by the NHTSA that manufacturers will modify
`their existing side curtain airbags through increased window coverage, increased inflation duration, and
`changes in tethering geometry to meet the standard. The agency asserted, “full window opening coverage was
`key to the effectiveness of the curtain in preventing ejection.” The phase-in schedule for FMVSS 226 requires
`that a percentage of vehicles meet the new requirement beginning September 1, 2013, and will require that all
`new vehicles meet the standard by September 1, 2017.
`To test for the 100 mm displacement criterion, an 18 kg (40 lb) headform is projected at impact
`speeds of 20 kph (12.4 mph) and 16 kph (10 mph), at 1.5 and 6 seconds, respectively, following curtain airbag
`deployment. It is stated in the Final Rule that these tests “replicate the forces that an occupant can impart to
`the curtain during the rollover event as well as during side impacts.” Impact target locations are determined
`based on the vehicle specific geometry of the side daylight openings. Pertaining to the specific ejection miti-
`gation countermeasure, the standard “does not allow the use of movable glazing as the sole means of meeting
`the displacement limit of the standard (i.e., movable glazing is not permitted to be used without a side curtain
`air bag).” Further, the second impact, executed at 6 seconds following curtain deployment, must be performed
`with the glazing retracted or removed from the daylight opening.
`The standard applies to passenger cars, trucks, buses, and multipurpose passenger vehicles with a
`gross vehicle weight rating of 4,536 kg (10,000 lb) or less. Compliance is required for the side windows next
`to the first three rows of seats and for a portion of the cargo area behind the first or second rows of these vehi-
`cles. Currently, the standard does not include the back light or roof portals as “the agency had no research and
`development foundation upon which requirements for the back light and roof portal could be based.” Vehi-
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`cles excluded from this standard include walk-in vans, modified roof vehicles, and convertibles, as well as law
`enforcement vehicles, correctional institution vehicles, and limousines based on their configuration and man-
`ufacturing and production history.
`Preceding the Final Rule, the Notice of Proposed Rulemaking (NPRM) pertaining to FMVSS No. 226,
`was issued on December 2, 2009. It is noteworthy that several of the proposed parameters for the standard
`were modified in the Final Rule. The first notable difference pertains to the use of advanced laminated glaz-
`ing. In the NPRM, the test procedure was drafted to “accommodate the use of advanced laminated glazing in
`fixed and in possibly moveable windows in addition to or in lieu of the side curtain air bag.” In the Final Rule,
`the use of movable glazing as the sole method of ejection mitigation is prohibited. Additionally, during the
`second impact, executed at 6 seconds following curtain deployment, the glazing must be retracted or removed
`from the daylight opening. Consideration of the initial position of the movable glazing as well as the condition
`of the glazing in rollover crashes led to these modifications with the NHTSA stating, “after considering real-
`world field data on advanced glazing that movable advanced glazing alone would not be a satisfactory ejection
`mitigation countermeasure for side window openings, given that 31% of front seat ejections are through win-
`dows that were partially or fully rolled down, and given that it is not unusual for advanced glazing to be heav-
`ily damaged and rendered ineffective in a rollover crash.”
`The second notable difference is the impact speed of the first test performed 1.5 seconds after curtain
`deployment. The impact speed of 20 kph (12.4 mph) was reduced from 24 kph (15 mph), as proposed in the
`NPRM. The NHTSA stated, “Some vehicle manufacturers have commented that meeting a 24 km/h require-
`ment will entail increasing air bag pressure in current bags, and have expressed concerns that more rigid bags
`will increase head injury criteria (HIC) values measured in a side impact tests and IARVs measured in out-of-
`position (OOP) tests. Although whether those increased HIC values and IARVs in OOP tests from increased
`air bag pressure pose an unreasonable safety risk is not known, negative trade-offs concern the agency in
`any rulemaking. Those possible trade-offs can be avoided with a 20 km/h requirement.” Further, a proposed
`impact energy level of 278 J, resulting from the test impact speed of 20 kph, “is well supported and more rep-
`resentative of the energy the ejection countermeasure will typically be exposed to in the field, particularly in
`rollovers.”
`Additionally, within the NPRM, the results of NHTSA’s work with their dynamic rollover fixture
`(DRF) were presented. Various inflatable countermeasures were tested including inflatable tubular structures
`and prototype curtain airbags. Partial ejections of test dummy extremities were observed, as well as complete
`ejection of a child dummy underneath a prototype curtain airbag. These results support the NHTSA’s state-
`ment that “full window opening coverage is key to the effectiveness of the curtain in preventing ejection.”
`Case Studies
`Dennis Stokes, as Personal Representative of the Estate of Peter Andrew Carter, Montana Thirteenth
`Judicial District Court, Yellowstone County, Cause No. DV 05-1236
`
` This matter involves the rollover a 2002 Ford Explorer. The rollover curtain was an optional
`feature on this vehicle. The decedent was belted and was not at fault in the accident. Plaintiff
`alleged that the Safety Canopy System should have been standard equipment and that this
`feature would be prevented the death of the decedent.
`Christine Zeolla, individually and as administrator of the estate of Mario Zeolla, United States District
`Court for the District of Massachusetts, Boston, 09-CV40106-FDS
`
` This matter involves the rollover of a 2003 Ford Expedition, which was equipped with a rollover
`curtain. The unrestrained decedent was sitting in the third-row sea,t and the rollover curtain
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`only covered the first two rows. Plaintiff alleged that the rollover curtain was defectively
`designed and should have covered the all three rows of seats. Plaintiff further alleged that the
`rollover curtain airbag would have prevented the ejection of the decedent and would have
`prevented his death.
`References
` 1. Bahling, G.S., et al.; “Rollover and Drop Tests – The Influence of Roof Strength on Injury
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`
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` 15. NHTSA; “Preliminary Regulatory Impact Analysis (PRIA), Notice of Proposed Rulemaking
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