Driver Lower Extremity Response and Injury With Knee Airbag Deployment

Lower extremity injury is the leading AIS2+ injury for drivers involved in frontal crashes. While there has been steady improvement in vehicle crash test performance over the past two decades, the risk of lower extremity injury remains virtually unchanged.

As one potential injury countermeasure, knee airbags and inflatable knee bolsters have been purportedly designed to mitigate lower limb forces and to improve overall occupant safety by providing early restraint for the pelvis and lower torso. Recent studies, however, suggest an increased injury risk of the tibia/fibula and the foot/ankle with knee airbags. This thesis aims to investigate the lower extremity response and injury with knee airbag deployment, and to identify any adverse effects the knee airbag imposes on lower extremity.

The thesis examines the lower extremity response for drivers in nominal driving posture, under dynamic condition with the presence of an Inflatable Knee Bolster (IKB). A total of seven unbelted sled tests (40 km/h) and eight belted sled tests (56 km/h) were performed with a 50th percentile Hybrid-III dummy to investigate the IKB effects on the lower limb. For the unbelted tests, the average tibia index (TI)increased by 34.6% and 33.3% for tests with IKB on the left upper (1.10±0.10) and left lower tibia(0.97±0.09), respectively, when compared to tests with standard knee bolster(left upper TI: 0.82±0.11; left lower TI: 0.73±0.05). Additionally, the right upper tibia index increased by 20.3% (from 0.64±0.10 to 0.77±0.04), while the right lower tibia index decreased by 26.5% (from 0.86±0.12 to 0.63±0.04). Similar results were found for the belted tests with IKB, where a 9.1% increase in risk of AIS 2+ tibia shaft fractures (from 11.8% to 20.9%) was predicted with IKB deployment.

The study also investigated the effects of the knee airbag on the lower limb injury risk for out-ofposition drivers. A total of eleven static knee airbag deployment tests were performed using a 5th percentile female Hybrid-III dummy outfitted with either the original Hybrid-III lower extremities or the 5 th percentile THOR-FLx. Baseline tests were performed with FMVSS 208 seating specifications, and a design of experiment for out-of-position conditions was developed with multiple factors including kneeto-instrument panel distance, knee-to-knee distance, and foot placement. The results predicted a 40.6% increase in risk of AIS 2+ tibia shaft fractures for out-of-position drivers (Ave. 53.6%) relative to inposition drivers (Ave. 13.0%).

This thesis indicates that inflatable knee bolsters can increase the likelihood of drivers sustaining tibia/fibula injuries in frontal crashes. In addition, the dummy lower extremity responses recorded in static deployment tests suggest a high risk of lower extremity injury for both in-position and out-ofposition small female drivers during knee airbag deployment. While this thesis covers a limited set of crash conditions and knee airbag designs, the results indicate the need for improved design of knee airbag for better protection of lower limb.

Year	Entry
2003	Swanson J, Rockwell T, Beuse N, Summers L, Summers S, Park B. Evaluation of stiffness measures from the U.S. new car assessment program. In: Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 19-22, 2003; Nagoya, Japan.
2003	Malczyk A, Kalliske I. Knee airbag effects on 5%ile female. In: Proceedings of the 2003 International IRCOBI Conference on the Biomechanics of Impact. September 25, 2003; Lisbon, Portugal.361-362.
2008	Ivarsson BJ, Manaswi A, Genovese D, Crandall JR, Hurwitz SR, Burke C, Fakhry S. Site, type, and local mechanism of tibial shaft fracture in drivers in frontal automobile crashes. Forensic Sci Int. 2008;175(2-3):186-192.
2001	Kuppa S, Wang J, Haffner M, Eppinger R. Lower extremity injuries and associated injury criteria. In: Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 4-7, 2001; Amsterdam, The Netherlands.
2005	Morris R, Cross G. Improved understanding of passenger behaviour during pre-impact events to aid smart restraint development. In: Proceedings of the 19th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 6-9, 2005; Washington, DC.
2002	Shams T, Beach D, Huang T-J, Rangarajan N, Haffner M. Development of THOR-FLx: a biofidelic lower extremity for use with 5th percentile female crash test dummies. Stapp Car Crash J. 2002;46:267-283. SAE 2002-22-0014.
2015	Nie B, Ye X, Riley P, Crandall JR, Panzer MB. Investigation of active muscle response on the occupant‐knee airbag interaction in frontal impacts. In: Proceedings of the 2015 International IRCOBI Conference on the Biomechanics of Injury. September 9-11, 2015; Lyon, France.130-132.
1998	Petit P, Portier L, Trosseille X. Rigid body model of the Hybrid III dummy lower limb including muscle tension under car crash conditions. In: Proceedings of the 1998 International IRCOBI Conference on the Biomechanics of Impact. September 16-18, 1998; Göteberg, Sweden.173-188.
2014	Ye X, Panzer MB, Shaw G, Crandall JR. Driver lower extremity response to out of position knee airbag deployment. In: Proceedings of the 2014 International IRCOBI Conference on the Biomechanics of Injury. September 10-12, 2014; Berlin, Germany.198-212.
2007	Hong S, Jung H, Cho B, Kim I. A study on invisible knee airbag cushion folding design using DOE (design of experimental) method. In: Proceedings of the 20th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 18-21, 2007; Lyon, France.
1983	Schneider LW, Robbins DH, Pflüg MA, Snyder RG. Development of Anthropometrically Based Design Specifications for an Advanced Adult Anthropomorphic Dummy Family, Volume 1. Ann Arbor, MI: University of Michigan Traffic Research Institute (UMTRI); December 1983. UMTRI Publication UMTRI-83-53-1.
1990	The Abbreviated Injury Scale-1990 Revision. Des Plaines, IL: Association for the Advancement of Automotive Medicine (AAAM); 1990.
1998	Welbourne ER, Shewchenko N. Improved measures of foot and ankle injury risk from the Hybrid III tibia. In: Proceedings of the 16th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 31–June 4, 1998; Windsor, Ontario, Canada.1618-1627.
1998	Håland Y, Hjerpe E, Lövsund P. An inflatable carpet to reduce the loading of the lower extremities: evaluation by a new sled test method with toepan intrusion. In: Proceedings of the 16th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 31–June 4, 1998; Windsor, Ontario, Canada.292-301.
2009	Leport T, Baudrit P, Petit P, Trosseille X, Vallancien G. Evaluation of the risk of injury caused by a knee airbag in out-of-position. In: Proceedings of the 21st International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 15-18, 2009; Stuttgart, Germany.
1993	Mertz HJ. Anthropomorphic test devices. In: Nahum AM, Melvin JW, eds. Accidental Injury: Biomechanics and Prevention. New York, NY: Springer-Verlag; 1993:66-84.
2001	Rudd RW, Crandall JR, Hjerpe E, Håland Y. Evaluation of lower limb injury mitigation from inflatable carpet in sled tests with intrusion using the Thor Lx. In: Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 4-7, 2001; Amsterdam, The Netherlands.
2003	Rudd R, Shaw G, Crandall J. Fifth percentile female Hybrid III and Thor-FLx performance in sled tests with toepan intrusion. In: Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 19-22, 2003; Nagoya, Japan.
2007	Faure J, Couturier S, Page Y, Labrousse M. The benefits of double pretension in decreasing knees & lower legs injuries in frontal impacts. In: Proceedings of the 20th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 18-21, 2007; Lyon, France.
2004	Funk JR, Rudd RW, Kerrigan JR, Crandall JR. The effect of tibial curvature and fibular loading on the tibia index. Traffic Inj Prev. June 2004;5(2):164-172.
1996	Crandall JR, Martin PG, Bass CR, Pilkey WD, Dischinger PC, Burgess AR, O'Quinn TD, Schmidhauser CB. Foot and ankle injury: the roles of driver anthropometry, footwear, and pedal controls. In: 40th Annual Proceedings, Association for the Advancement of Automotive Medicine (AAAM). October 7-9, 1996; Vancouver, BC.1-18.
2013	Reed MP, Ebert SM, Hallman JJ. Effects of driver characteristics on seat belt fit. Stapp Car Crash J. November 2013;57:43-57.
1999	Shams T, Beach D, White RP, Rangarajan N, Haffner M, Eppinger R, Kuppa S, Beebe M. Development and design of Thor-Lx: the Thor lower extremity. In: Proceedings of the 43rd Stapp Car Crash Conference. October 25-27, 1999; San Diego, CA. Warrendale, PA: Society of Automotive Engineers:141-160. SAE 99SC09.
2010	Bose D, Crandall JR, Untaroiu CD, Maslen EH. Influence of pre-collision occupant parameters on injury outcome in a frontal collision. Accid Anal Prev. July 2010;42(4):1398-1407.

Year

Entry

2003

Swanson J, Rockwell T, Beuse N, Summers L, Summers S, Park B. Evaluation of stiffness measures from the U.S. new car assessment program. In: Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 19-22, 2003; Nagoya, Japan.

2003

Malczyk A, Kalliske I. Knee airbag effects on 5%ile female. In: Proceedings of the 2003 International IRCOBI Conference on the Biomechanics of Impact. September 25, 2003; Lisbon, Portugal.361-362.

2008

Ivarsson BJ, Manaswi A, Genovese D, Crandall JR, Hurwitz SR, Burke C, Fakhry S. Site, type, and local mechanism of tibial shaft fracture in drivers in frontal automobile crashes. Forensic Sci Int. 2008;175(2-3):186-192.

2001

Kuppa S, Wang J, Haffner M, Eppinger R. Lower extremity injuries and associated injury criteria. In: Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 4-7, 2001; Amsterdam, The Netherlands.

2005

Morris R, Cross G. Improved understanding of passenger behaviour during pre-impact events to aid smart restraint development. In: Proceedings of the 19th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 6-9, 2005; Washington, DC.