Size and age of fatal drivers by crash type, vehicle type and gender.

Objective: The objective of this study was to determine the physical characteristics of fatal drivers in motor vehicle crashes with focus on rear impacts.Methods: 1998 to 2020 FARS data was analyzed for height, weight, and age of fatal drivers. The data was queried by gender, crash type and vehicle type.Results: The average fatal driver weighed 80.4 kg, was 173.4 cm tall, and was 43 years old. Females were 16.0 kg lighter and 14.2 cm shorter than males on average. The height was 151.2 cm for the 5th percentile female, 177.0 cm for the 50th male and 188.9 cm for the 95th male. The weight of fatal drivers increased linearly with calendar year. The increase rate was greater in females than in males. About 3% of fatal drivers were involved in rear crashes, 39.9% in frontal crashes and 36.8% in rollovers. The average fatal driver was 172.5 cm tall and weighed 81.0 kg in rear impacts. They were similar in height and weight to the overall sample. The average fatal driver in rear impacts was 46 years old, 3 years older than the overall average. Pickup truck drivers weighed 85.4 kg and were 176.8 cm tall on average. They were heavier and taller than passenger car drivers on average, which were 78.0 kg and 172.2 cm. Fatally injured minivan drivers were 10 years older than fatally injured passenger car drivers on average. The findings are compared with ATDs (anthropometric test devices) used in sled and crash testing.Conclusion: The average weight of fatal drivers increased with calendar year. The average size of fatal drivers was similar by crash types. Fatal drivers were older in rear impacts.

The effect of seatback deformation on out-of-position front-seat occupants in severe rear impacts.

OBJECTIVE: This study assesses the effects of seat deflection in severe oblique rear impacts with laterally out-of-position ATDs where the head is not supported by the head restraint. METHOD: Six high-speed rear sled tests were conducted at 48 km/h with a 195 degree PDOF. A lap-shoulder belted 50th percentile Hybrid III ATD was leaned inboard and seated in six different front passenger seats (A-F); five of the seats were selected from mid-sized sedans and one was a non-production rigidified Seat Integrated Restraint (SIR) seat. FRED-III pull tests resulted in seat stiffnesses that varied from 73 to 172 N/mm. Seat F had the greatest stiffness. The seat and ATD responses were assessed. The biomechanical responses were evaluated and compared to relevant IARVs. RESULTS: In all tests the ATD moved rearward and twisted the seat. There was limited differential motion of the torso relative to the seatback. The ATD position and PDOF prevented head restraint engagement allowing head and neck extension over the seatback. The seatback angle was measured on the inboard side. At maximum yield, it was greatest with Seat E, followed by Seat A and Seat D, at 71, 67 and 62 degrees, respectively. The duration of rearward deformation was also greatest with Seat A, Seat D and Seat E providing longer ride-down. The head, chest and upper neck responses were below IARVs. Lower-neck extension moments were above injury threshold with Seat B, C and F. Seat F had the highest lower-neck moment. CONCLUSION: Seats with greater deformation provided the greatest ride-down durations and the lowest overall biomechanical responses. The combination of high impact severity and lack of head support resulted in high lower-neck responses, highlighting the potential benefit of energy management from deforming seat structures.

Serious-to-fatal injury to second-row occupants in rear impacts using 1994-2020 field data.

OBJECTIVE: Serious-to-fatal injury was analyzed for second-row children aged 0-14 years and adults aged 15 and older in rear impacts by body region, restraint use, and injury mechanism using field data collected by NHTSA. METHOD: 1994-2015 NASS-CDS and 2017-2020 CISS data were used to investigate the rate for Maximum Abbreviated Injury Scale (MAIS) 3 + F injury in rear crashes involving 1994+ model year vehicles. All second-row occupants were included, irrespective of restraint use and ejection status. The data were analyzed by group: children (0-14 years old) and adults (15+ years old). All available electronic files for seriously injured second-row occupants in the rear impacts were reviewed for mechanism of injury. RESULTS: The rate of serious injury (MAIS 3 + F) for second-row occupants was 0.93% ± 0.36% in rear crashes; it was 0.76% ± 0.39% for children and 1.22% ± 0.40% for adults. There were 2.8 AIS 3+ injuries per seriously to fatally injured occupant on average. Most serious injuries occurred to the head in children and to the head and chest in adults. Restraint use was only 31.3% for all seriously injured second-row occupants in the rear impacts. It was 45.1% for children and 17.8% for adults. The overall rate of serious injury in rear impacts was 10.0 times higher when unrestrained than restrained overall; it was 5.6 times higher for children and 20.2 times higher in adults. The case review indicated that many young children were improperly restrained or placed in the incorrect child seat. More than 17% of second-row adults were ejected; all were unrestrained. The primary mechanism for child injury was related to intrusion (86.0%). About 14% was not related to intrusion; 12.3% involved the front seat rotating rearward into the child. The primary mechanisms for adult injury differed from those for children; 68.0% was related to intrusion, 21.6% was not related to intrusion, and 10.4% involved ground impact with ejection. Of the non-intrusion-related cases, 19.1% involved acceleration forces injuring the adult and 2.5% involved the front seat rotating rearward. CONCLUSIONS: The primary mechanism for serious injury to second-row occupants in rear crashes was intrusion either by direct force, compression into front components, or acceleration into forward components. The front seat moving rearward was an infrequent cause for injury.

Safety priorities for occupant protection in rear impacts.

OBJECTIVE: Rear-impact electronic cases were reviewed for serious injury to rear-seated children and adults to identify mechanisms of injury and consider priorities, countermeasures and safety concepts. METHODS: 1997-2015 NASS-CDS and 2017-2020 CISS electronic cases were analyzed for serious injury (MAIS 3+F) to rear-seated children 0-14 yo (years old) and adults 15+ yo in rear impacts. RESULTS: 31 children and 43 adults were identified with serious injury. 86.0% of child injury was related to intrusion of rear structures with injury by direct force (55.3%), compression into front interior (27.5%) or acceleration into impact (3.2%). 14.0% of injury was not related to intrusion with front-seatback rotation (12.3%) or direct force (1.7%). Only 45.1 ± 17.6% of injured children were properly restrained. 68.0% of adult injury was related to intrusion of rear structures with injury by direct force (46.2%), compression into front interior (15.3%) and acceleration into impact (6.4%). 21.6% of injury was not related to intrusion with front seatback rotation (2.5%) or direct force (19.1%). 10.4% was from ejection and ground impact without seatbelt use. Only 17.8 ± 7.5% of injured adults were restrained. Priorities, countermeasure and concepts were considered to improve occupant protection in rear impacts: 1) new rear impact test with the IIHS high-hood barrier offset to the rear at 55 mph to reduce rear-seat intrusion, 2) stepped-up campaigns for proper child seat selection and use, particularly for infants and toddlers <2 yo and adult use of seatbelts in rear seats, 3) adoption of FMVSS 201L to reduce head injury risks of children impacting the rear interior below the beltline, 4) improved front seats by shifting restraining forces from the seatback to the cushion frame with an anti-ramping guide that retains the pelvis on the seat and reduces seatback rotation, 5) changes in front seatbelts to provide early restraint of occupant movement by a rear-impact pretensioner that moves the lap-belt anchors and gives a favorable angle for early lap-belt restraint or a rear wrap-around lap belt so the occupant moves into the belt in a rear impact, 6) implementation of kinematic controls on front-occupant movement that reduces ramping in severe rear impacts, 7) guarding the area around rear-seated child with an after-market ring structure that maintains space around the child and blocks rearward rotation of the front seatback and 8)-25) recommendations. CONCLUSIONS: The primary mechanism for injury to rear-seated children and adults is intrusion, often without appropriate occupant restraint. There are priorities to improve protection by reducing intrusion, guarding the area around children, shifting front-occupant loads to the cushion frame and improving occupant restraints.

Significance of tractor-trailer impacts to the rear of light vehicles.

OBJECTIVE: This study determined the type of striking vehicle or object associated with serious injury to at least 1 occupant in the vehicle struck in the rear. METHOD: The 1990-2015 NASS-CDS was analyzed for light vehicles involved in rear crashes. The type of vehicle struck in the rear resulting in serious injury to at least 1 occupant was determined. Rear impacts were identified with GAD1 = B without rollover (rollover ≤ 0). Vehicles with serious to maximum injury were identified as VAIS 3 to 6 (VAIS 3+). The type of striking vehicle or object was determined for the rear impacts causing serious injury. The risk and relative risk for serious injury were determined. Review of electronic cases was conducted for light vehicles with serious injury (VAIS 3+) in impacts by tractor-trailers or large trucks. RESULTS: The highest risk for serious injury to an occupant in the struck vehicle was from a tractor-trailer or large truck (2.71%), followed by a fixed object (1.49%) and van (1.00%). The average risk was 0.33%. The relative risk was 8.2 times for impact with a tractor-trailer or large truck and 4.5 times for impact with a fixed object. The highest risk impacts with a fixed object were rear impacts into a tree/bush (3.57%) and pole (2.90%). Tractor-trailers and large trucks accounted for 16.2% of serious injury in struck vehicles, followed by fixed objects at 12.9%; the 2 accounted for 29.1% of serious injury to occupants of struck vehicles. The case review identified 22 tractor-trailer and 1 large truck crashes involving 31 seriously injured occupants in the struck vehicle. There were 2 general crash scenarios associated with serious injury. One involved intrusion deforming the occupant compartment. The other involved vehicle accelerations sufficient to seriously injure an occupant in the struck vehicle without significant deformation to the occupant compartment. CONCLUSION: This study provides insight into the striking vehicle or object associated with serious injury to light vehicle occupants in rear impacts. Tractor-trailer impacts into the rear of a vehicle involved a high risk for serious injury in the struck vehicle. The use of collision mitigation technologies, such as forward collision warning or automatic emergency braking, on the tractor-trailer may support better speed control and lead to lower closing velocities of rear impacts to light vehicles.

Thoracic and lumbar spine responses in high-speed rear sled tests.

OBJECTIVE: This study analyzed thoracic and lumbar spine responses with in-position and out-of-position (OOP) seated dummies in 40.2 km/h (25 mph) rear sled tests with conventional and all-belts-to-seat (ABTS) seats. Occupant kinematics and spinal responses were determined with modern (≥2000 MY), older (<2000 MY), and ABTS seats. METHODS: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap-shoulder belted in the FMVSS 208 design position or OOP, including leaning forward and leaning inboard and forward. There were 26 in-position tests with 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS and 14 OOP tests with 6 conventional and 8 ABTS seats. The dummy was fully instrumented. This study addressed the thoracic and lumbar spine responses. Injury assessment reference values are not approved for the thoracic and lumbar spine. Conservative thresholds exist. The peak responses were normalized by a threshold to compare responses. High-speed video documented occupant kinematics. RESULTS: The extension moments were higher in the thoracic than lumbar spine in the in-position tests. For <2000 MY seats, the thoracic extension moment was 76.8 ± 14.6% of threshold and the lumbar extension moment was 50.5 ± 17.9%. For the ≥2000 MY seats, the thoracic extension moment was 54.2 ± 26.6% of threshold and the lumbar extension moment was 49.8 ± 27.7%. ABTS seats provided similar thoracic and lumbar responses. Modern seat designs lowered thoracic and lumbar responses. For example, the 1996 Taurus had -1,696 N anterior lumbar shear force and -205.2 Nm extension moment. There was -1,184 N lumbar compression force and 1,512 N tension. In contrast, the 2015 F-150 had -500 N shear force and -49.7 Nm extension moment. There was -839 N lumbar compression force and 535 N tension. On average, the 2015 F-150 had 40% lower lumbar spine responses than the 1996 Taurus. The OOP tests had similar peak lumbar responses; however, they occurred later due to the forward lean of the dummy. CONCLUSIONS: The design and performance of seats have significantly changed over the past 20 years. Modern seats use a perimeter frame allowing the occupant to pocket into the seatback. Higher and more forward head restraints allow a stronger frame because the head, neck, and torso are more uniformly supported with the seat more upright in severe rear impacts. The overall effect has been a reduction in thoracic and lumbar loads and risks for injury.

Effectiveness of the revision to FMVSS 301: FARS and NASS-CDS analysis of fatalities and severe injuries in rear impacts.

PURPOSE: This study investigated the change in the fatality and severe injury risks in rear impacts with vehicle model years (MY) grouped prior to, during the phase-in and after the revision to FMVSS 301. METHODS: FARS and NASS-CDS data were used to determine the injury risks of non-ejected occupants in light vehicles involving non-rollover, rear impacts. The data were analyzed by MY groups: 1996-2001, 2002-2007 and 2008+ to represent the years prior to, during the phase-in and post-revision phase-in of FMVSS 301. The 1996-2013 FARS data were analyzed for rear crashes defined by the initial crash direction (IMPACT1) and direction with most damage (IMPACT2) to the rear. Fatality risk was determined by the number of fatally injured occupants per all occupants with known injury status. The 1994-2013 NASS-CDS was analyzed for rear crashes defined by the damage area variable. The risk of severe injury (MAIS 4+F) was determined as the number of occupants with MAIS 4+F injury per all occupants with known injury status. The distribution of rear crashes was determined by impact location and crash severity. NASS-CDS electronic cases with 2008+ MY vehicles were analyzed to evaluate the vehicle and occupant performance. RESULTS: The fatality risk was 20.6% in the 1996-2001, 17.3% in the 2002-2007 and 15.0% in the 2008+ MY vehicles using FARS with the initial crash direction variable (IMPACT1) to the rear. There was a 27.1% reduction in risk with post-FMVSS 301 vehicles 2008+ MY. The risk was 19.0%, 15.4% and 12.8% with the most damage variable (IMPACT2) to the rear. There was 32.8% reduction in risk with 2008+ MY vehicles. The NASS-CDS analysis showed that the risk of severe injury (MAIS 4+F) was 0.27±0.05% for 1996-2001, 0.30±0.13% for 2002-2007 and 0.08±0.04% for 2008+ MY year vehicles. There was a 70.2% reduction in the risk for severe injury with 2008+ MY vehicles. The NASS-CDS case review of MAIS 4+F injury in rear impacts of 2008+ MY vehicles that comply with the revised FMVSS 301 indicated that the crashes were very severe and generally involved significant 2nd row intrusion. CONCLUSIONS: The revision to FMVSS 301 has effectively reduced the risks for fatal and severe injury in vehicles compliant with the revision (2008+ MY). The reduction was 27.1-32.8% in fatality risk using FARS data and 70.2% in severe injury risk using the NASS-CDS when compared to vehicles prior to the phase-in of the revised FMVSS 301 (1996-2001 MY vehicles). It is not possible to parse the effects of other design changes in seats and restraint systems that also increased safety over the study years.