Frontal NCAP crash tests with rear-seat occupant.

OBJECTIVES: The initial frontal NCAP tests in 1979 included lap-shoulder belted driver and right-front passenger and lap belted 6-year-old (yo) in the rear. The 35 mph barrier tests were reviewed and analyzed for the restraint performance of the front occupants and child in the rear. METHODS: The initial 100 crash tests (#1-#100) in the NHTSA database were searched for frontal barrier impacts. Fifteen tests met the criteria. There were three tests with the 1980 Chevrolet Citation at 35, 40 and 48 mph. There were 12 other tests with different passenger vehicles at 35 mph into the rigid barrier. The tests included a lap-shoulder belted Hybrid II (Part 572) dummy in the driver and right-front passenger seat and a lap belted 6 yo child dummy (Alderson VIP 6 C) in the center or right rear seat. Vehicle dynamics and occupant kinematics were analyzed, and dummy responses were compared. RESULTS: Vehicle deformation was progressive with impact speed for the Citation tests, leading NHTSA to settle on a 35 mph NCAP speed. The thirteen 35 mph NCAP tests had an average driver HIC of 1099 ± 381 (95th CI 207) and 3 ms chest acceleration of 55.7 ± 16.1 g (95th CI 8.8) with 7 of 13 vehicles failing FMVSS 208 injury criteria. The average right-front passenger HIC was 1179 ± 555 (95th CI 302) and 3 ms chest acceleration was 47.2 ± 14.6 g (95th CI 7.9) with 7 of 13 failing injury criteria. Only four tests (30.8%) passed driver and right-front passenger injury criteria.The responses in the rear seat were significantly worse. The average HIC was 2711 ± 1111 (95th CI 604) and 3 ms chest acceleration was 62.8 ± 10.6 g (95th CI 5.8). The films showed the child's upper body moved forward and rotated downward around the lap belt resulting in severe head impacts on the front seatback, floor, dummy legs or interior. All vehicles failed injury criteria by large margins. Submarining the lap belt was noted in 6 tests. HIC for the rear child was 2.47-times greater than the driver (t = 4.72, p < 0.001) and 2.30-times greater than the right-front passenger (t = 3.64, p < 0.005). CONCLUSIONS: In the 1979 NCAP tests, the child dummy experienced inadequate restraint by the lap belt in the rear seat. The child jackknifed around the lap belt, often submarined, with a severe head impact. No publication of the results has been found. NHTSA did not advise the public of the extremely poor restraint performance, even during the public discussions on the 1986 NTSB recommendation that U.S. vehicle manufacturers install lap-shoulder belts in rear outboard seats. None of the subsequent NCAP tests included a child or adult in the rear until nearly 25 years later.

History of airbag safety benefits and risks.

OBJECTIVE: The history of airbags was reviewed for benefits and risks as they became a supplement to lap-shoulder belts. Sled and crash tests were evaluated and field data was analyzed for airbag effectiveness. Field data on airbag deaths and studies on mechanisms of deployment injury were analyzed. The history was reviewed as airbags evolved from the early 1970s to today. METHODS: Airbag benefits were determined from NHTSA crash tests with unbelted and belted dummies in 40, 48, and 56 km/h (25, 30, and 35 mph) frontal impacts with and without airbags. The literature was reviewed for testing of passive restraints with and without airbags. Recent NCAP tests were compared with earlier tests to determine the change in occupant responses with seatbelts and supplemental airbags in modern vehicles. 1994-2015 NASS-CDS field data was analyzed for MAIS 4 + F injury. Risks were compared for belted and unbelted occupants in frontal impacts by delta V. Airbag risks were identified from field deployments and research. The 1973-76 GM fleet had two deaths due to the occupant being out-of-position (OOP). The mechanisms of injury were determined. From 1989-2003, NHTSA investigated 93 driver, 184 child passenger, and 13 adult passenger airbag deaths. The data was reviewed for injury mechanisms. Second generation airbags essentially eliminated OOP airbag deaths. More recently, three suppliers were linked to airbag rupture deaths. The circumstances for ruptures were reviewed. RESULTS: The risk for serious head injury was 5.495% in drivers and 4.435% passengers in 40-48 km/h (25-30 mph) frontal crash tests without belts or airbags. It was 80.5% lower at 1.073% in drivers and 82.0% at 0.797% in passengers with belts and airbags in 35 mph NCAP crash tests of 2012-20 MY vehicles. NASS-CDS field data showed a 15.45% risk for severe injury (MAIS 4 + F) to unbelted occupants and 4.68% with belted occupants in 30-35 mph frontal crash delta V with airbags, as deployed. The reduction in risk was 69.7% with belt use and airbags deploying in 96.1% of crashes. There were benefits over the range of delta V. Two airbag deaths were studied from the 1970s GM fleet of airbags. The unbelted driver death was caused by punchout force with the airbag cover blocked by the occupant and membrane forces as the airbag wrapped around the head, neck or chest with the occupant close to the inflating airbag. The unbelted child death was from airbag inflation forces from pre-impact braking causing the child to slide forward into the deploying airbag. Research showed that unrestrained children may have 13 different positions near the passenger airbag at deployment. NHTSA investigation of first generation airbag deaths found most driver deaths were females (75.3%) sitting forward on the seat track, close to the driver airbag. Seatbelt use was only 30%. Most child deaths (138, 75.4%) involved no or improper use of the lap-shoulder belts. Of these, 115 deaths involved pre-impact braking. Only 37 (20.2%) children were in child seats with 29 in rear-facing and 8 in forward-facing child seats. Eight child deaths (4.4%) occurred with lap-shoulder belt use. Airbag designs changed. More recently, Takata airbags were related to at least 24 deaths by airbag rupture prompting a recall; the successor company Joyson had an airbag recall. ARC airbags have experienced a chunk of the inflator propelled into the driver during deployment with several deaths leading to a recall. CONCLUSIONS: Airbags are effective in preventing death and injury in crashes. They provide the greatest protection in combination with seatbelt use. NHTSA estimated airbags saved 28,244 lives through 1-1-09 while causing at least 320 deployment deaths, which has prompted improved designs, testing, and recalls.

Frontal NCAP performance and field injury over 40 years.

OBJECTIVES: Vehicle and occupant responses in 35 mph NCAP tests were determined for small-midsize passenger cars grouped around model year (MY) 1980, 1990, 2000, 2010 and 2020. A baseline was established with 1980 vehicles not designed for NCAP. The results of four decades of vehicles designed for NCAP were compared to the baseline. The study also determined the risk for serious injury (MAIS 3 + F) by vehicle model year (MY) using 1989-2015 NASS and 2017-2020 CISS. It explored safety trends in frontal crashes over 50 MYs of vehicles. METHODS: The 1980 baseline group was established with 10 1979-1983 MY passenger cars weighing <1,500 kg. Four decades of vehicle crash tests from five manufacturers established trends in vehicle dynamics and dummy responses over four decades of vehicles designed for NCAP. Triaxial acceleration of the head and chest were reanalyzed for each test to have a consistent set of responses over five decades. The risk for serious injury (MAIS 3 + F) to the driver and front passenger was determined by vehicle MY using 1989-2015 NASS and 2017-2020 CISS with belted and unbelted drivers and right-front passengers. The data was sorted in four MY groups 1961-1989 MY, 1990-1999 MY, 2000-2009 MY and 2010 MY-2021 MY. The risk for MAIS 3 + F injury was determined with standard errors using weighted data. RESULTS: The 1980 NCAP tests brought about changes in vehicle structures and occupant restraints by 1990; however, HIC15 and 3 ms chest acceleration have not changed much the past 20 years since the use of advanced airbags and seatbelts with pretensioner and load-limiters. For the driver, HIC15 dropped 40 ± 19% from the 1980 to 1990 NCAP tests and dropped further to 76 ± 32% in 2020. The percentage drops after 1990 were not statistically significant. The driver 3 ms chest acceleration dropped 18 ± 5% from 1980 to 1990 and plateaued with 22 ± 6% in 2020. For the front passenger, HIC15 dropped 68 ± 52% from the 1980 to 1990 NCAP tests and plateaued at 71 ± 49% in 2020. The passenger 3 ms chest acceleration dropped 13 ± 5% from 1980 to 1990 and has fluctuated with minimal change. Injury risks based on responses show the same initial drop in 1990 and have remained essentially constant. Nothing meaningful has changed in dummy responses in the past 20 years of NCAP testing. The field data found the belted driver MAIS 3 + F risk was 1.66 ± 0.37% in 1961-1989 MY vehicles and 1.39 ± 0.33% in 2010-2021 MY vehicles. For belted right-front passengers, the risk was 1.52 ± 0.39% in 1961-1989 MY vehicles and 1.42 ± 0.46% in 2010-2021 MY vehicles. The field data shows no meaningful change in injury risk in 50 MYs of vehicles. NCAP involves 35-40 mph delta-V, which represents a small fraction, 0.33%, of belted occupant exposure and only 8.6% of severe injury based on 1994-2015 NASS. CONCLUSIONS: The NCAP test lacks field relevance. Manufacturers are merely "tuning" the restraint systems for star ratings without meaningful changes in field injury risks the past 20 years. There are disbenefits of "tuning" safety for a single, high-severity crash when most of the severe injury occurs in lower severity crashes. NHTSA should reevaluate plans to change the dummy to Thor and add BrIC injury criteria to assess NCAP responses. These changes would cause manufacturers to further "tune" structures, restraints and interiors without meaningful effects in real-world crashes.

Injury and death to armored passenger-vehicle occupants and ground personnel from explosive shock waves.

This study evaluated the risks for injury and death to occupants from blast waves to the side and underbody of an armored passenger-vehicle and to ground personnel from free-field blast waves. The Kingery-Bulmash empirical relationships for explosive shock waves were augmented by the Swisdak empirical relations for stand-off distances up to Z = 39.8 m/kg1/3 to tabulate shock-wave characteristics using the Friedlander wave-shape. A 15 kg, hemispherical explosion was analyzed in detail for the shock wave velocity and compression of air behind the wave front. An armored SUV was analyzed with Z = 1.6 m/kg1/3 (4 m) standoff distance from pressure loading on the near-side, far-side and underbody. The rigid body displacement was 0.36 m and 7.8° yaw for a side loading. When a segment of the occupant compartment accelerates inward, there are risks for injury from the intrusion. Energy is transferred to the occupant by deformation of their body (Ed) and by velocity increasing the kinetic energy of the body region (Ek). Body deformation injures an occupant by exceeding the tolerable compression (crush mechanism) or exceeding the rate-dependent tolerance, which is defined by the rate times the extent of compression (viscous mechanism). The risk for injury and death to ground personnel was analyzed for free-field blast waves by stand-off distance and TNT weight. A 15 kg charge posed a 99% risk of death at 3.9 m, 50% risk at 5.2 m, 1% risk at 7.8 m and injury threshold at 8.2 m. A 100 kg charge posed a 99% risk of death at 8.5 m, 50% risk at 11.6 m, 1% risk at 17.3 m and injury threshold at 18.0 m. The study describes the steps to analyze blast loading of an armored passenger-vehicle for risks of occupant injury. It describes the steps to analyze injury risks to ground personnel from blast wave pressure.

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.

Using the NINDS Consensus Diagnostic Criteria for Traumatic Encephalopathy Syndrome on 4 Cohorts of Retired Contact Sport Athletes.

BACKGROUND: A 2021 National Institute for Neurological Disorders and Stroke (NINDS) consensus panel proposed a set of clinical diagnostic criteria for traumatic encephalopathy syndrome (TES) and determined provisional levels of certainty for chronic traumatic encephalopathy (CTE) pathology based on neuropathological evidence. The panel suggested the criteria needed to be validated by clinical studies of living populations exposed to repetitive head impacts (RHIs). HYPOTHESIS: As the consensus criteria were developed solely from neuropathologically diagnosed cases of CTE, we hypothesized that they may not be readily applicable to the clinical impressions developed from the histories and examination findings of living patients whose neuropathology was unknown. STUDY DESIGN: We applied the consensus criteria to 4 groups of living retired contact sports athletes collected from previously published articles in the medical literature. LEVEL OF EVIDENCE: Level 4. METHODS: Clinical evidence from 4 groups of living retired athletes (boxers and American football players) with extensive RHI exposure was available. We used the NINDS consensus criteria to determine for each athlete whether or not they met the criteria for TES. For those who met the criteria, we determined their provisional level of certainty for CTE pathology. RESULTS: Among all 80 subjects, the prevalence of TES was 21.3% (17 of 80), the prevalence of possible CTE was 12.5% (10 of 80), and the prevalence of probable CTE was 2.5% (2 of 80). Among the 45 retired football players, the prevalence of TES was 24.4% (11 of 45) and the prevalence of possible CTE was 17.7% (8 of 45). None of the retired football players met the criteria for probable CTE. Among the 35 total retired boxers (from all 3 groups), the prevalence of TES was 17.1% (6 of 35), the prevalence of possible CTE was 5.7% (2 of 35), and the prevalence of probable CTE was 5.7% (2 of 35). CONCLUSION: Applying the NINDS consensus criteria to this historical cohort of living retired athletes with extensive RHI exposure resulted in a relatively low prevalence of TES and possible/probable certainties of CTE pathology, which might suggest limitations on the sensitivity of the NINDS criteria. CLINICAL RELEVANCE: Physicians are often asked by retired contact sports athletes and their families to determine if their clinical picture is related to TES and/or CTE. Physicians may turn to the NINDS consensus criteria for guidance in making such determinations. The data presented here may assist physicians in evaluating the reliability and validity of using the consensus criteria in living subjects.

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.

Quasi-static methods to evaluate seat strength in rear impacts.

OBJECTIVE: Various methods have been used in the past 50 years to apply Quasi-static load to a seat in the rear direction and measure seat performance in rear impacts. This study compared five of the most-common test procedures to evaluate seats. In addition, occupant mass and center of gravity are discussed as important characteristics of rear loading of seats. METHOD: Data was collected and analyzed from five different seat pull tests, including FMVSS 207, modified FMVSS 207, QST, body block and FRED II. Test data included peak force, moment and angle at peak moment. Occupant loading height of was determined using body segment weights and position in the forward (x) and vertical (z) directions based on anthropometry data. RESULTS: Some of the inherent differences in the tests are shown by comparing data with the same seat structure. The QST and FRED II use a lower height of loading than FMVSS 207. The QST and FRED II peak moment and force did not coincide with the same seatback angle as in FMVSS 207 and body block testing. Center of gravity height varies depending on whether the whole body or only the upper torso is considered. For the 50th male, it is 171.5 mm (6.8") with the whole body and 246.7 mm (9.7") with the upper torso. CONCLUSION: Results from different tests cannot be readily compared because of different loading conditions, including body shape and height of load about the H-point, which can cause the seat structure to respond differently.

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.

Motion sequence criteria for favorable occupant kinematics in rear impacts.

OBJECTIVE: Rear-impact restraint guidelines have not developed to the same degree as for frontal crashes. This study provides criteria for favorable occupant kinematics in rear impacts. METHODS: Rear criteria were developed as an extension of Adomeit and Heger (1975) and Adomeit (1977) motion sequence criteria (MSC) for favorable occupant kinematics in frontal crashes. In this study, occupant kinematics in rear sled tests were studied to develop motion sequence criteria for favorable and unfavorable occupant kinematics in rear impacts with containment of the hip on the seat and no ramping up the seatback. RESULTS: Rear MSC limit the angle of the torso (α) rearward of vertical to less than the critical angle (αc) for ramping up the seatback and H-pt displacement rearward and downward, so zHpt < zHpt0, where zHpt0 is the initial height of the H-pt. The lateral displacement of the occupant is limited to less than the critical lateral displacement yT1c, where the head becomes unsupported by the head restraint or the chest by the seatback. The rear MSC contain the pelvis on the seat and provide uniform support of the torso, head and neck. Most front seats in production provide reasonably favorable occupant kinematics in rear impacts up to 40 km/h (25 mph) delta V with the 50th Hybrid III. Kinematics become unfavorable in testing at higher severities and with heavier occupants. The amount of energy that the seat needs to transfer to the occupant in a rear impact depends on the delta V (ΔV or change in velocity) of the vehicle and the mass of the occupant (m) among other variables. The seat provides an interface with the occupant and transfers energy (E), which can be approximated by E = ½*0.7*m(ΔV)2 using 70% of the occupant mass (m) and delta V. Rear MSC provide performance guidelines to advance seat designs with favorable occupant kinematics at higher energy transfer levels in rear impacts. Sled testing at 40 km/h (25 mph) involves an energy transfer of 3,421 J with the 50th Hybrid III generally gives favorable kinematics. A 56.3 km/h (35 mph) test involves 6,704 J, double the energy transfer and often unfavorable kinematics. A target energy needs to be set, and there are practical limits because the energy transfer is 12,858 J with a 150 kg (330 lb) occupant in a 56.3 km/h (35 mph) delta V rear crash. CONCLUSION: Rear motion sequence criteria (MSC) define favorable kinematics in rear impacts. MSC complement the assessment of biomechanical responses in sled and crash testing to ensure an overall evaluation of occupant restraint in rear impacts.

Fetal deaths and maternal injury in motor-vehicle crashes using NASS-CDS and CISS field data.

OBJECTIVE: This study determined the risk for fetal death and maternal injury in the same sample of motor-vehicle crashes. The frequency and risk of serious injury (MAIS 3 + F) were also assessed by sex, pregnancy, seating position and crash type. METHOD: The 2008-2015 NASS-CDS and 2017-2020 CISS are representative samples that were analyzed for the risk of fetal death and the risk of maternal injury grouped by MAIS 0-2, MAIS 3 + F and death (F) in 2000+ model year (MY) light vehicles. All electronic cases involving fetal mortality were reviewed for mechanism of injury. Separately, the 2000-2015 NASS-CDS and 2017-2020 CISS data was analyzed for the risk of serious injury for male, female and pregnant female occupants by seating position and crash type in 2000+ MY light vehicles. All calculations are made with weighted data. The significance of differences in risk was determined by the Rao-Scott chi-square test in SAS and z-test for differences in proportions. RESULTS: There were 2,467 ± 1,407 fetal deaths in light vehicle crashes from 2008-2015 and 2016-2020 with an annual occurrence of 206/yr. The risk for fetal death was 1.25% ± 0.74% of exposed pregnant females. There were 127 ± 67 deaths of pregnant females, or 11/yr in the same sample. The fatality risk was 0.065% ± 0.035%. The difference in proportions was statistically significant (z = 46.1, p < 0.0001). Fetal deaths occurred 19.4-times more often than deaths of pregnant females. In 82.9% of the crashes with a fetal death, the pregnant female was not seriously injured (MAIS 3 + F). The most common mechanism of fetal death was a minor crash, in 80.1% of the weighted cases based on review of photos of the case vehicle and observing very minor structural damage to the vehicle. The minor crash involved either yaw of the occupant compartment with side loading of the pregnant female or her displacement into the restraint system and side interior in 71.7% of the crashes. A severe crash with intrusion at the seating position of the pregnant female occurred in only 11.5% of cases. It usually caused serious injury to the pregnant female and fetal death. CONCLUSIONS: Fetal deaths occurred 19.4-times more often than deaths of pregnant females in a 12-year sample of motor-vehicle crashes. The most common mechanism was a minor crash that resulted in a fetal death without serious injury to the pregnant female and involved side or oblique loading of the pregnant female.

Analysis of the lack of restraint with and without belt pretensioning in 40.2 km/h rear impacts.

OBJECTIVE: In rear impacts, the seat and seatbelt are intended to provide occupant restraint and maintain the occupant on the seat with favorable kinematics and low biomechanical responses. This study analyzes the lack of restraint provided by lap-shoulder belts in rear impacts with and without pretensioning and offers thoughts on ways to provide early restraint by seatbelts. METHODS: Rear sled tests were conducted at 40.2 km/h (25 mph) delta V with a lap-shoulder belted, instrumented 50th Hybrid III. The dummy instrumentation included head, chest and pelvis triaxial acceleration and upper and lower neck triaxial loads and moments. Lap and shoulder belt loads were measured. High-speed video recorded different views of the occupant kinematics. In the first series, two sled tests were conducted with a Ford F-150 driver seat. One test was with the standard lap-shoulder belts only and a second with buckle pretensioner activation. In the second series, three matched tests were conducted with a Ford Escape driver seat. One test was with the lap-shoulder belts only, a second with retractor and anchor pretensioning and a third with only retractor pretensioning. The analysis included occupant kinematics, lap-belt movement and estimation of the load on the occupant's torso. The load was the sum of force on the upper and lower torso. The upper torso mass was 30.8 kg (67.8 lb) based on GEBOD data for the 50th Hybrid III. It was multiplied by the resultant chest acceleration to calculate the upper torso force. The lower-torso mass was 30.9 kg (68.0 lb). It was multiplied by the resultant pelvic acceleration to calculate the lower torso force. The total load on the seatback was the sum of the upper and lower torso force. The change in angle (θ) of the lap belt was determined by video analysis. The angle θ was from the horizontal up to a line through the lap-belt webbing. Ways to provide early lap-belt restraint were considered. RESULTS: The rear sled testing at 40.2 km/h (25 mph) showed that the seatbelt provided essentially no restraint of the rearward movement of the occupant. The seat provided essentially all of the rearward restraint with and without pretensioning. There was minimal lap belt load in the series with the dual recliner Escape seat, except for a spike caused by pretensioning. There was more seat deformation in the tests with the single-side recliner F-150 seat. There were higher belt loads. The lap belt limited the lifting of the hips and thighs with essentially no rearward restraint of the occupant. Tension in the lap belt did not relate to restraint of rearward movement of the occupant. Seatbelts provided forward restraint of the occupant during rebound with the belts providing noticeable deceleration of the chest and pelvis. Concepts were considered to provide early lap-belt restraint. One involved a rear pretensioner that dynamically moves the lap-belt anchor forward and upward while tightening the belts in a rear impact. This provides a lap-belt angle greater than θ = 90 deg before occupant movement. With this geometry, the lap belt restrains rearward movement of the occupant and pulls the hip down early in a rear impact. CONCLUSION: Seatbelts and pretensioners were designed for occupant restraint in frontal crashes, so it is not a surprise they do not provide much restraint of an occupant in rear impacts up to 40.2 km/h (25 mph). The lack of early lap-belt restraint is due to the unfavorable belt angle from the anchors over the hip. A concept is discussed that dynamically moves the anchors in rear impacts to provide early belt restraint.

Basilar, skull and facial fractures in 2nd row occupants by crash type with a focus on side and rear impacts.

OBJECTIVE: Field data was analyzed to assess the risk of basilar, skull and facial fractures in 2nd row occupants by crash type. The study determined the rate of fractures in seriously injured (MAIS 3 + F) occupants to establish priorities for 2nd row occupant safety. METHODS: Field accident data on seriously injured (MAIS 3+) occupants was determined using 1993-2015 NASS-CDS and 2017-19 CISS by crash type identified with damage area variables for non-ejected occupants in the 2nd row. Occupants with serious head and face injuries (AIS 3+) were subdivided by fractures to the skull, basilar skull and face. Moderate-to serious (AIS 2+) orbit fractures were included. The rate of injury was determined. Individual electronic cases were analyzed for occupants with basilar fracture in rear and side impacts. RESULTS: The proportion of 2nd row occupants with AIS 3+ head and face injury was highest at 73.7% in rear impacts followed by side impacts at 54.2% for those with MAIS 3 + F injury. Basilar fractures (AIS 3+) occurred in 53.9% of 2nd row occupants with skull fracture in rear impacts but only 20.3% in side impacts. Overall, basilar fractures occurred in 10.8% of 2nd row occupants with serious injury (MAIS 3 + F) in rear impacts and 2.7% in side impacts. The frequency of AIS 3+ facial fractures was highest in side impacts (40.2%) and lowest (7.6%) in rear impacts. CONCLUSIONS: While basilar skull fractures are rare in 2nd row occupants, at 0.083% in rear and 0.044% in side impacts, they represent 53.9% of 2nd row occupants with a skull fracture and serious injury in rear impacts and 20.3% in side impacts. The mechanism of injury is different in rear and side impacts, but frequently involves multi-impact crashes, severe impacts, intrusion into the seating area and head impact on hard surfaces.

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.

Evaluations of pretensioner activation in rear impacts.

OBJECTIVE: Occupant kinematics and biomechanical responses are assessed with and without pretensioning of normally seated and out-of-position front-seat occupants in rear sled tests. The results are compared to recent studies. METHODS: Three series of rear sled tests were conducted at 24 and 40 km/h with a 2001 Ford Taurus. Series I consisted of two sled tests with a lap-shoulder belted 50th Hybrid III in the driver seat. Series II included four sled tests with a lap-shoulder belted 50th Hybrid III in both front seats. Two soft foam blocks were added, one was placed on the chest centerline under the shoulder belt and one on the pelvis under the lap belt providing additional webbing. Series III consisted of 8 runs and 16 ATD tests to assess the effect of pretensioning with out-of-positioned (OOP) occupants. The biomechanical responses were normalized with Injury Assessment Reference Values (IARV) for head, neck and chest. RESULTS: The ATD kinematics and biomechanical responses were similar in the yielding phase when the occupant was normally seated with and without pretensioning. The rebound displacement was greater with pretensioning in the 40 km/h tests due to the shoulder belt slipping off the shoulder. The hip displacement was similar, irrespective of pretensioning. All biomechanical responses were below IARVs. The highest response was for lower neck extension. The normalized response was at about 32% for the 24 km/h tests, irrespective of pretensioning. It was up to 59% in the 40 km/h tests with pretensioning. With the OOP occupants, there were no differences in the kinematics and biomechanical response with pretensioning. CONCLUSIONS: Testing of the effect of retractor pretensioning with out-of-position occupants and additional belt webbing in moderate to high-speed rear sled tests shows no effect on occupant kinematics and biomechanical responses. The displacement of the hips in a rear impact depends on the compliance of the seatback and amount of pocketing, the stiffness of the seat frame limiting rearward rotation, and the dynamic friction between the occupant and the seatback.

Change in seating position of children in towaway crashes from 1989 to 2019.

OBJECTIVE: The purpose of this study was to examine the impact of the nationwide response to passenger airbag (PA) related deaths of children. The response was implemented in 1996 and focused on moving children to rear seats. This study determined the change in seating position of children from 1989 to 2019. METHODS: Field accident data on exposed occupants in towaway crashes was determined using 1989-2015 NASS-CDS in five groups (1989-1995, 1996-99, 2000-04, 2005-09 and 2010-15) and 2017-19 CISS in one group. Children were grouped as 0-2 yo (years old), 3-7 yo and 8-12 yo. Occupants 13 + were included for completeness. Seat position was defined as left-front (LF), right-front (RF), 2nd row and 3rd row. The weighted data provided an estimate for the change in seating position over time by occupant age with standard errors. RESULTS: For 0-2 yo, 27.9% were in the RF seat in 1989-95. The fraction decreased to 0.40% in the 2017-19 (p < 0.001). For 3-7 yo, 32.1% were in the RF seat in 1989-95 and 3.2% in 2017-19 (p < 0.001). There has been a steady decrease in 0-7 yo using the RF seat. For 8-12 yo, there was a step decline in use of the RF seat from 39.5% in 1989-95 to 23.2% in the 2017-19 (p < 0.001). CONCLUSIONS: The immediate reduction in front-seat use among younger children was associated with the nationwide public information efforts implemented in 1996 to move children to rear seats. Children up to 7 yo are no longer riding in the RF seat of vehicles in towaway crashes, unless there is no other option. Children 8-12 yo are still using the RF seat, but at a lower rate. The change in use of the RF seat for children 0-7 yo provides evidence that safety campaigns on placing young children in rear seats were successful in the US.

Influence of retractor and anchor pretensioning on dummy responses in 40 km/h rear sled tests.

OBJECTIVE: This study compared dummy kinematics and biomechanical responses with and without retractor pretensioning in a severe rear sled test. It compliments an earlier study with buckle pretensioning. METHODS: Three rear tests were run at 40 km/h (25 mph) delta V with a lap-shoulder belted Hybrid III 50th male dummy on a 2013-18 Ford Escape driver seat and belt restraint. One test was with the lap-shoulder belts only, a second with retractor and anchor pretensioning and a third with only retractor pretensioning. The head, chest and pelvis were instrumented with triaxial accelerometers. The upper and lower neck, thoracic spine and lumbar spine had transducers measuring triaxial loads and moments. Lap belt load was measured. High-speed video recorded different views of the dummy motion. Dummy kinematics and biomechanical responses were compared to determine the influence of retractor belt pretensioning. RESULTS: The dummy kinematics and biomechanical responses were essentially similar with and without retractor or retractor and anchor pretensioning in rear sled tests. There was an initial spike in lap belt load with pretensioning, but it did not result in different dummy head, neck or chest responses. In the tests, the dummy moved rearward away from the shoulder belt. The belts were tightened with the rapid pull on the webbing by pretensioning. The dummy loaded the seat, which yielded rearward restraining its motion. There was no significant effect of pretensioning on the dynamics of the dummy until late in rebound. CONCLUSIONS: There were no significant differences in dynamics of the Hybrid III with and without retractor or retractor and anchor pretensioning in a 40 km/h (25 mph) rear sled test. Belt pretensioning did not influence biomechanical responses in the rear impact because the seat supported the dummy.

Rear-seat occupant demographics in rear impacts: Analysis of NASS-CDS.

PURPOSE: This study analyzes field accidents to identify rear-occupant exposure and injury by crash types. Occupant demographics and injury were assessed by body region and crash severity to understand rear-occupant injury mechanisms in rear crashes. METHODS: The exposure and serious-to-fatal injury was determined by crash type for non-ejected second- and third- row occupants in 1994+ MY vehicles using 1994-2015 NASS-CDS. Selected occupant demographics and serious injury distributions were assessed over a range of delta V for rear crashes. RESULTS: Rear crashes accounted for 8.7% of exposed and 5.4% of serious-to-fatally injured rear-seat occupants. On average, rear-seat occupants were 14.3 ± 1.5 years old (median 10.3, 90th CI 0.08-29.6), weighed 44.7 ± 2.6 kg (median 44.4, 90th CI 7.9-81.7) and were 130.3 ± 4.1 cm tall (median 141.4, 90th CI 67.3-178.4). With serious injury, the average rear occupant was 18.1 ± 5.8 years old (median 13.1, 90th CI 0.0-47.2), weighed 42.6 ± 10.7 kg (median 31.4, 90th CI 7.0-82.4) and was 120.6 ± 15.4 cm tall (median 145.4, 90th CI 48.8-174.1). More than 72% of rear-seat occupants were in delta V less than 24 km/h. Less than 2% were in delta V 48 km/h or greater. The overall rate of serious-to-fatally injured (MAIS 3 + F) was 0.73% ± 0.37%. For serious-to-fatally injured rear-seat occupants, the average delta V was 37.4 ± 3.1 km/h (median 29.8, 90th CI 28.6-62.1). None were involved in delta Vs less than 24 km/h, about 78% were in a delta V between 24-48 km/h and 22% were in a delta V of 48 km/h or greater. Head and chest were most commonly injured, irrespective of crash severity. CONCLUSIONS: The height and weight of a 10-year old and 5th Hybrid III ATD are representative of the average rear-seat occupant involved in rear crashes based on NASS-CDS. Crash tests with a delta V of between 30 and 37 km/h represent the typical collision causing serious-to-fatal injury.

Effect of ABTS and conventional seats on occupant injury in rear impacts: Analysis of field and test data.

PURPOSE: This study addressed the potential effect of higher seat stiffness with ABTS (All-Belt-to-Seat) compared to conventional seats in rear impacts. It analyzed field accidents and sled tests over a wide range in delta V and estimated the change in number of injured occupants if front-seats were replaced with stiffer ABTS. METHODS: The rear-impact exposures and serious-to-fatal injury rates were determined for 15+ year old non-ejected drivers and right-front passengers in 1994+ model year vehicles using 1994-2015 NASS-CDS. More than 50 rear sled tests were analyzed using conventional and ABTS seats. An injury risk was calculated for selected ATD biomechanical responses. The results obtained with the ABTS and conventional seats were compared for matched tests based on head restraint position, ATD size and initial position and delta V. The change in risk was used to estimate the change in injury in the field by adjusting the injury rate by delta V. RESULTS: On average, front seat occupants were 39 years old, weighed 78 kg and were 171 cm tall. About 29.3% of serious-to-fatally injured (MAIS 3 + F) front seat occupants were involved in delta Vs less than 24 km/h and about 28.4% in a delta V of 48 km/h or greater. The average biomechanical response and injury risk in sled tests were higher with an ABTS seat than with a conventional seat. The average maximum injury risk was assessed by delta V groups for conventional and ABTS seats. The relative risk of ABTS to conventional seats was 1.34 in less than 16 km/h, 1.69 in 16-24 km/h, 1.65 in 24-32 km/h, 1.33 in 32-40 km/h, 5.77 in 40-48 km/h and 48.24 in the 56-64 km/h delta V category. The estimated relative risk was 11.90 in 48-56 km/h and 34.11 in 64+ km/h. The number of serious-to-fatally injured occupants was estimated to increase by up to 6.88-times if stiffer ABTS seats replaced conventional seats. CONCLUSIONS: The field data indicate that the 50th percentile male Hybrid III size is representative of an average occupant involved in rear crashes. ABTS seats used in this study are stiffer than conventional seats and increase ATD responses and injury risks over a wide range of crash severities.