Injury Assessment Reference Values Research Articles

Development of a Restraint System for Rear-Facing Car Seats

In self-driving vehicles, passengers can set their seats in an unconventional seating position, such as rear-facing. Sitting in such an orientation can increase the risk of whiplash in the head-and-neck system in a frontal impact, as frontal crashes usually have higher severities compared with rear-end crashes. This paper shows that a forward-facing front seat optimised for rear-impact protection needs to be redesigned to be used as a rear-facing seat. In the second and main part of this paper, a restraint system for rear-facing car seats is developed, and frontal impact simulations with 64 km/h of delta-V are used to evaluate its performance. The designed seating system comprises two rigid torso plates, a fixed recliner and an energy absorber under the seat pan. Without using the developed restraint system, the 50th percentile male human model is exposed to neck shear forces exceeding 600 N. With the developed restraint system, neck shear forces are less than 350 N in frontal impacts with 64 km/h of delta-V. Apart from whiplash, the risk of head, chest, lower extremity and lower back injuries are also evaluated. The results confirm that the developed restraint system successfully protects the occupant since all assessment criteria values are lower than the injury assessment reference values.

A Biomechanical Assessment of Shaken Baby Syndrome: What About the Spine?

Shaken baby syndrome occurs following inertial loading of the pediatric head, resulting in retinal hemorrhaging, subdural hematoma, and encephalopathy. However, the anatomically vulnerable cervical spine receives little attention. Automotive safety literature is replete with biomechanical data involving forward-facing pediatric surrogates in frontal collisions, an environment analogous to shaking. Publicly available data involving child occupants were utilized to study pediatric neck and head injury potential. We hypothesized that inertial loading provides a greater risk of injury to the cervical spine than to the head. Full-scale automotive crash tests (n= 131) and deceleration sled tests (n= 32) utilizing forward-facing 3-year-old surrogates with head accelerometers and cervical force sensors were analyzed. One hundred sixty-seven full-scale vehicle and 33 sled test runs were assessed in the context of published injury assessment reference values (IARVs) for closed head injury (head injury criterion 15 [HIC15]) and cervical tensile strength in the 3-year-old model. One hundred sixty-one (96%) child surrogates in full-scale crash tests exceeded the cervical peak tension IARV, while only 37 (22%) surpassed the HIC15 IARV. Similarly, in sled testing runs, 27 (82%) pediatric surrogates exceeded cervical tension IARVs, while 1 (3%) surpassed the HIC15 IARV. In both full-scale and sled tests, all surrogates surpassing the HIC15 IARV also exceeded the cervical tension IARV. Positive linear correlations were observed between HIC15 and cervical tensile forces in both full-scale vehicle (R2= 0.15) and sled testing runs (R2= 0.54). These data support the hypothesis that inertial loading of the head provides a greater injury risk to the cervical spine than to closed-head injury.

Rear-End Impacts - Part 2: Sled Pulse Effect on Front-Seat Occupant Responses

<div class="section abstract"><div class="htmlview paragraph">This study was conducted to assess the effects of differing rear impact pulse characteristics on restraint performance, front-seat occupant kinematics, biomechanical responses, and seat yielding. Five rear sled tests were conducted at 40.2 km/h using a modern seat. The sled buck was representative of a generic sport utility vehicle. A 50<sup>th</sup> percentile Hybrid III ATD was used. The peak accelerations, acceleration profiles and durations were varied. Three of the pulses were selected based on published information and two were modeled to assess the effects of peak acceleration occurring early and later within the pulse duration using a front and rear biased trapezoidal characteristic shape.</div><div class="htmlview paragraph">The seatback angle at maximum rearward deformation varied from 46 to 67 degrees. It was lowest in Pulse 1 which simulates an 80 km/h car-to-car rear impact. The seatback plastic deformation was greater in the pulse with the rear biased trapezoidal acceleration profile, Pulse 4, than in the front biased trapezoidal acceleration profile, Pulse 5 (46 degrees v 41 degrees). Coincidingly, the longitudinal head displacement was slightly greater in the Pulse 4. There was limited relative motion between the ATD torsos and the seatbacks. The relative motion between the ATD torso and the seatback was less than 7 cm in all tests. The head, chest and pelvis peak acceleration and timing varied depending on the pulse. All peak head, chest, pelvis and upper and lower-neck moments occurred prior to maximum seatback dynamic deflection. The biomechanical responses were all well below injury assessment reference values. The seatback structural restitution was the highest in Pulse 1 which had the lowest amount of dynamic and plastic seatback deformation and had the highest lap belt load. All peak belt loads occurred in the rebound phase of the ATD.</div><div class="htmlview paragraph">The sled coordinate-based data was used to determine the effective restraint stiffness. The results were used to develop a spring-mass model. The model will help understand the effects of pulse characteristics on predicted chest acceleration for future research.</div><div class="htmlview paragraph">In conclusion, the results from this study show that pulse shape has a measurable effect of seat and ATD kinematics in high-speed rear impacts and should considered for future research and testing.</div></div>

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.

An evaluation of occupant dynamics during moderate-to-high speed side impacts.

The present study examined trends in occupant dynamics during side impact testing in vehicle models over the past decade. "Moderate-to-high" speed side impacts (delta-V ≥15 km/h) were analyzed. The Insurance Institute for Highway Safety (IIHS) side impact crash data was examined (N = 126). The test procedure involved a moving deformable barrier (MDB) impacting the sides of stationary vehicles at 50.0 km/h. Instrumented 5th-percentile female SID IIs dummies were positioned in the driver and left rear passenger seats. Occupant head, neck, shoulder, torso, spine, and pelvis/femur responses (times histories, peaks, and time-to-peak values) were evaluated and compared to injury assessment reference values (IARVs). The effects of delta-V, vehicle model year, vehicle body type, and occupant seating position on dynamic responses were examined. The vehicle lateral delta-Vs ranged from 15.9 to 34.5 km/h. The MY2018-2020 demonstrated lower peak dynamics than MY2010-2013, for the driver head acceleration (53.7 ± 11.3g vs 46.4 ± 11.6g), shoulder lateral forces (1.7 ± 0.7 kN vs 1.5 ± 0.2 kN), average rib deflection (29.8 ± 8.3 mm vs 28.4 ± 6.2 mm), spine accelerations at T4 (51.4 ± 23.4g vs 39.6 ± 5.9g) and T12 (56.3 ± 18.5g vs 45.2 ± 9.6g), iliac forces (1.9 ± 1.0 kN vs 1.2 ± 0.9 kN), and acetabular forces (1.9 ± 0.8 kN vs 1.3 ± 0.5 kN). The driver indicated statistically higher dynamic responses than the left rear passenger. Higher wheelbase vehicles generally showed lower occupant loading than the smaller vehicles. In conclusion, a reduction in occupant loading and risks for injury was observed in vehicle models over the past decade. This provides further insight into injury mechanisms, occupant dynamics simulations, and seat/restraint design.

Second-row occupant responses with and without intrusion in rear sled and crash tests

Purpose Intrusion of the occupant compartment increases the risks for severe injury and death. This study analyzes rear sled and crash tests with an instrumented second-row Hybrid III 5th percentile anthropometric test device (ATD) to assess occupant kinematics and biomechanical responses with and without intrusion of the second-row seatback. Methods Three sled tests and four crash tests were conducted with a 1993 Ford Taurus and a belted 5th female ATD seated behind a belted 50th male ATD on the right-side of the vehicle. The sled tests were conducted at 25, 33 and 40 km/h and involved no intrusion. The first crash test was conducted with a passenger car striking the vehicle at 80 km/h with full centerline overlap. The second to fourth crash tests were with a Sport Utility Vehicle (SUV) striking with a 50% overlap. Tests 2 and 3 were at 51 km/h and test 4, at 80 km/h impact speed. A large wooden speaker box was placed in the trunk of the Taurus in tests 3 and 4. Second-row intrusion was measured at the right-rear outboard package shelf retractor. Results The sled tests without intrusion had occupant responses below injury assessment reference values (IARVs). The right second-row ATD moved rearward relative to the interior, compressing the rear seatback until it rebounded forward. Occupant compartment intrusion of 12–77 cm in the crash tests pushed the ATD forward, increasing head and chest acceleration. The head, neck and chest biomechanical responses were below IARVs in crash tests 1 to 3 with minimal intrusion (≤ 25 cm). Most of the biomechanical responses were above IARVs for the right second-row ATD in test 4 with higher intrusion. The HIC increased with intrusion. Head acceleration was more than 2.5-times greater in test 3 than in test 2, highlighting the importance of cargo in rear crashes. Test 4 had 2.4-times more energy than test 3 and up to 7.7 times greater biomechanical responses with 77 cm of intrusion. Conclusions The crash tests show that intrusion increases occupant responses in the right second-row seat and pushes the occupant forward in rear impacts. The sled tests without intrusion had relatively low biomechanical responses. Intrusion was influenced by the crash energy and cargo.

Lower neck injury criteria for THOR and Hybrid III dummies in rear impact

Objective The objectives of the study are to derive lower-neck-injury probability curves under rear impact loading from matched pair Hybrid III and THOR dummy tests. Methods Twelve whole-body and 15 isolated head-neck rear-impact sled tests were conducted using the 2 dummies. They were positioned on a rigid seat that was attached to an acceleration sled. The dummies were positioned with the head parallel to the ground, torso against the seat back, and legs stretched such that there was no axial rotation. The acceleration pulse matched the previous in-house human cadaver tests. The 6-axis lower-neck load cell was used in both dummies. For the isolated rear-impact tests, the head-neck was excised from the dummies, and the lower-neck load cell was mounted to the top of the sled with the head parallel to the ground and such that the acceleration vector was in the rear impact mode. Lower-neck loads and lower-neck-injury criteria (LNij) were obtained using the load cell data and survival analysis was used to develop injury-assessment-risk values and curves for both dummies. The LNij criteria were determined for both dummies using the intercept value corresponding to the 90% probability level for the forces and moments. Results The lognormal and Weibull distributions were the optimal distributions for the Hybrid III and THOR devices. At the 50% risk level, the mean LNij was 1.1 and NCIS was 0.77 for the Hybrid III, and 1.5 and 0.30 for the THOR device. The quality indices were in the fair range and good range for the 2 dummies, respectively, at this risk level. Conclusions The lower neck based LNij injury assessment risk curves and reference values, IARCs and IARVs, serve as the first dataset for injury assessments, and the THOR may be a better test device for assessing injures in rear impact environments.

Windblast testing of an aircrew helmet: An approach to neck load analysis

Introduction: Modern generation fighter aircraft has expanded the escape envelope for a fighter aircrew. With the ejection occurring at very high airspeeds, windblast is a cause of major injuries and fatalities. Flying helmet, before its induction into operational usage, must be tested in simulated windblast conditions to ensure that they provide adequate safety. Material and Methods: Windblast tests were conducted on a newly designed/procured helmet in a standard windblast test facility as per Mil Std MIL-V-29591/1. A large instrumented Hybrid III male dummy was used for the tests. The test conditions were: Wind speed 600 ± 60 KEAS, rise time of 125 ± 20 ms, time at peak wind velocity of 300 ± 50 ms, and total exposure time of ≥3 s. Structural integrity, retention with the headform, and recorded neck loads were assessed for interpretation of test results. Results: Helmets could withstand the windblast conditions without any significant structural failures and were retained with the headform during the entire duration of test conditions. However, analysis of the neck loads resulted in a significant dilemma in aeromedical decision-making, there being no laid down criteria in the Mil Specification. The neck tension forces were more than the acceptable limits and found to have the potential for significant neck injuries as per the Injury Assessment Reference Values specified in AGARD-AR-330 specifically in the tests where blast was head on and outer visor in up configuration; however, these values were within the acceptable limits as per the other proposed criteria. Similarly, analysis of the neck tension extension combined effects revealed conflicting outcomes for Nij performance limits specified in various standards. This paper discusses the critical analysis of neck loads vis-à-vis the neck injury criteria to understand the neck loads generated during windblast conditions and its implication on aircrew safety. Conclusion: Neck loads assessment is critical in predicting aircrew safety during windblast testing. In the absence of a clearly defined criteria in the Mil Specification, critical ananlysis of neck loads vis-à-vis recommended standards in scientific literature be done to make meaningful conclusion.

Examining ski area padding for head and neck injury mitigation

ObjectivesThe injury mitigation capabilities of foam, ski-area padding was examined for headfirst impacts. Design and MethodsA custom-made pendulum impactor system was constructed using an instrumented, partial 50th-percentile-male Hybrid-III anthropomorphic testing device (ATD). For each test, the ATD was raised 1.0m, released, and swung into a 20-cm diameter wooden pole. Test trials were conducted with the wooden pole covered by ski area padding (five conditions of various foam types and thicknesses) or unpadded. Linear (linear acceleration and HIC15) and angular (angular velocity, angular acceleration, and BrIC) kinematics were examined and used to estimate the likelihood of severe brain injury. Cervical spine loads were compared to the injury assessment reference values for serious injury. Further tests were conducted to examine the changes produced by the addition of a snowsport helmet. Results38 test trials were recorded with a mean (±sd) impact speed of 4.2 (±0.03) m/s. Head, resultant linear acceleration, HIC15, and associated injury likelihoods were tempered by ski area padding at the impact speed tested. Ski area padding did not reduce brain injury likelihood from rotational kinematics (p>0.05 for all comparisons) or reduce the cervical spine compression below injury assessment reference values. The addition of a helmet did not reduce significantly the likelihoods of brain or cervical spine injury. ConclusionsAt the impact speed tested, ski area padding provided limited impact protection for the head (for linear kinematics) but did not protect against severe brain injuries due to rotational kinematics or serious cervical spine injuries.

Countermeasures design and analysis for occupant survivability of an armored vehicle subjected to blast load

The demand for blastworthy structures increases due to a large number of casualties in the armored vehicle undergoing improvised explosive device (IED) and landmine attacks. In this research, the numerical studies on the countermeasure analysis to reduce injury biomechanics risk were conducted. The available experiment data of occupant survivability test on a medium size tank was used to validate the numerical model. The subsystem evaluation in this study included the finite element modeling of military personnel, seat system, surrounding interior system, seatbelt, and restraint system with four running conditions. The military personnel inside the armored vehicle was modeled by using Hybrid III 50th percentile anthropomorphic test device (ATD) and its biomechanical response was monitored on the head, neck, thorax, spine, femur, and tibia. The load case for this study referred to NATO STANAG 4569 level 3b with 8 kg TNT explosive load underbelly. The injury assessment reference values (IARV) for the regulation used in this study were based on AEP-55 volume 2. Based on this study, the critical injuries identified on the head injury, neck compression, and tibia axial load. The solid frame as part of seat structure appeared to contribute to an excessive kinematic on the lower extremities. The vehicle acceleration resulted from the load blast was directly transmitted to the lower extremities, resulting in unintended kinematic and interaction on the passenger body. The proposed solutions were to introduce a flexible mounting for the seat system and as well increasing the height of the footrest to avoid direct transmission of vehicle acceleration. The modified countermeasure design reduced significantly head, neck, and tibia injury criteria more than 90 % from the baseline design (existing design). The new anti-mine seat design successfully passed all the standard regulation thresholds of injury criteria.

Head and neck injury potential during water sports falls: examining the effects of helmets

Head and neck injuries sustained during water skiing and wakeboarding occur as a result of falls in water and collisions with obstacles, equipment, or people. Though water sports helmets are designed to reduce injury likelihood from head impacts with hard objects, some believe that helmets increase head and neck injury rates for falls into water (with no impact to a solid object). The effect of water sports helmets on head kinematics and neck loads during simulated falls into water was evaluated using a custom-made pendulum system with a Hybrid-III anthropometric testing device. Two water entry configurations were evaluated: head-first and pelvis-first water impacts with a water entry speed of 8.8 ± 0.1 m/s. Head and neck injury metrics were compared to injury assessment reference values and the likelihoods of brain injury were determined from head kinematics. Water sport helmets did not increase the likelihood of mild traumatic brain injury compared to a non-helmeted condition for both water entry configurations. Though helmets did increase injury metrics (such as head acceleration, HIC, and cervical spine compression) in some test configurations, the metrics remained below injury assessment reference values and the likelihoods of injury remained below 1%. Using the effective drag coefficients, the lowest water impact speed needed to produce cervical spine injury was estimated to be 15 m/s. The testing does not support the supposition that water sports helmets increase the likelihood of head or neck injury in a typical fall into water during water sports.

차륜형장갑차 차체의 지뢰방호구조 설계 연구

In this study, to develop mine protective design technology for wheeled armored vehicles, designing and simulating of test specimens based on the 8×8 military combat vehicle, were executed and mine protection effectiveness was proven, by testing under the two work steps such as 1st step for conceptual model and 2nd step for vehicle segment. Experiments for both test models of each step were performed according to test conditions of NATO standard, STANAG 4569 Level, and simulations were performed by the commercial code, LS-DYNA. On the 1st step, a conceptual model was designed, and its protection effectiveness was verified by simulation before testing and then it was proven by testing. On the 2nd step, the vehicle segment with protection design technology from the 1st step was designed better, to consider dynamic vertical deformation, injury values of a human dummy, and effects of installed components on the bottom of the model. Finally, satisfaction for protection effectiveness and IARVs (Injury Assessment Reference values) of a human dummy were verified by testing, and also the possibility of application for wheeled armored vehicles were confirmed.

Cervical spine injury in rollover crashes: Anthropometry, excursion, roof deformation, and ATD prediction

While rollover crashes are rare, approximately one third of vehicle occupant fatalities occur in rollover crashes. Most severe-to-fatal injuries resulting from rollover crashes occur in the head or neck region, due to head and neck interaction with the roof during the crash. While many studies have used anthropomorphic test devices (ATDs) to predict head and neck injury, the biofidelity of ATDs in rollover has not been established. This study aims to build on previous research to compare the dynamic response and injuries sustained by four post mortem human surrogates (PMHS) to those predicted by six different ATDs in full-scale rollover crash tests. Additionally, this study evaluates injuries sustained by PMHS relative to possible contributing factors including occupant kinematics, occupant anthropometry, and vehicle roof deformation. While the vehicle kinematics and roof deformation were comparable for all tests, three out of the four PMHS sustained cervical spine injury, but only the tallest specimen sustained cervical spine fracture. Neck flexion at the time of head-to-roof contact appears to have affected cervical spine injury risk in these cases. Despite the injuries sustained in the PMHS, none of the six ATDs measured forces or accelerations that exceeded injury assessment reference values (IARVs), which adds to recent literature illustrating substantial differences between ATDs and PMHS in a rollover-like scenario.

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

ABSTRACTObjective: 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.

Top tether effectiveness during side impacts

ABSTRACTObjective: Few studies have looked at the effectiveness of the top tether during side impacts. In these studies, limited anthropomorphic test device (ATD) data were collected and/or few side impact scenarios were observed. The goal of this study was to further understand the effects of the top tether on ATD responses and child restraint system (CRS) kinematics during various side impact conditions.Methods: A series of high-speed near-side and far-side sled tests were performed using the FMVSS213 side impact sled buck and Q3s ATD. Tests were performed at both 10° and 30° impacts with respect to the pure lateral direction. Two child restraints, CRS A and CRS B, were attached to the bench using flexible lower anchors. Each test scenario was performed with the presence and absence of a top tether. Instrumentation recorded Q3s responses and CRS kinematics, and the identical test scenarios with and without a top tether attachment were compared.Results: For the far-side lateral (10°) and oblique (30°) impacts, top tether attachment increased resultant head accelerations by 8–38% and head injury criterion (HIC15) values by 20–140%. However, the top tether was effective in reducing lateral head excursion by 5–25%. For near-side impacts, the top tether resulted in less than 10% increases in both resultant head acceleration and HIC15 in the lateral impact direction. For near-side oblique impacts, the top tether increased HIC15 by 17.3% for CRS A and decreased it by 19.5% for CRS B. However, the injury values determined from both impact conditions were below current injury assessment reference values (IARVs). Additionally, the top tether proved beneficial in preventing forward and lateral CRS rotations.Conclusions: The results show that the effects of the top tether on Q3s responses were dependent on impact type, impact angle, and CRS. Tether attachments that increased head accelerations and HIC15 values were generally counterbalanced by a reduction in head excursion and CRS rotation compared to nontethered scenarios.

Reconstruction of a Rollover Crash for Thoracic Injury Etiology Investigation

The cause of serious and fatal thoracic injuries in passenger vehicle rollover crashes is currently not well understood. Previous research on thoracic injuries resulting from rollover crashes have focused primarily on statistical analysis of crash data. This study seeks to develop a better understanding of where in the rollover sequence thoracic injuries may occur. To do this, a real-world passenger vehicle rollover crash where the driver sustained serious bilateral thoracic injuries was reconstructed. Multi-body analysis was used to determine the vehicle’s pre-trip trajectory and to obtain the vehicle’s position and kinematics at the point of trip. This information was then used to prescribe the motion of the vehicle in a finite element analysis. A finite element model of the EuroSID-2re anthropomorphic test device was placed in the driver’s seat. Four simulations, each with the anthropomorphic test device positioned in different postures, were performed. Rib deflection, spinal acceleration, and thoracic impact velocity were obtained from the anthropomorphic test device and compared to existing thoracic injury assessment reference values. From the analysis, lateral thoracic impact velocity indicates that a serious thoracic injury is likely to have occurred when the driver impacted the centre console during the vehicle’s fourth quarter-turn.

Optimizing Seat Belt and Airbag Designs for Rear Seat Occupant Protection in Frontal Crashes.

Recent field data have shown that the occupant protection in vehicle rear seats failed to keep pace with advances in the front seats likely due to the lack of advanced safety technologies. The objective of this study was to optimize advanced restraint systems for protecting rear seat occupants with a range of body sizes under different frontal crash pulses. Three series of sled tests (baseline tests, advanced restraint trial tests, and final tests), MADYMO model validations against a subset of the sled tests, and design optimizations using the validated models were conducted to investigate rear seat occupant protection with 4 Anthropomorphic Test Devices (ATDs) and 2 crash pulses. The sled tests and computer simulations were conducted with a variety of restraint systems including the baseline rear-seat 3-point belt, 3-point belts with a pre-tensioner, load limiter, dynamic locking tongue, 4-point belts, inflatable belts, Bag in Roof (BiR) concept, and Self Conforming Rear seat Air Bag (SCaRAB) concept. The results of the first two sled series demonstrated that the baseline 3-point belt system are associated with many injury measures exceeding injury assessment reference values (IARVs); showed the significance of crash pulse and occupant size in predicting injury risks; and verified the potential need of advanced restraint features for better protecting the rear-seat occupants. Good correlations between the tests and simulations were achieved through a combination of optimization and manual fine-tuning, as determined by a correlation method. Parametric simulations showed that optimized belt-only designs (3-point belt with pre-tensioner and load limiter) met all of the IARVs under the soft crash pulse but not the severe crash pulse, while the optimized belt and SCaRAB design met all the IARVs under both the soft and severe crash pulses. Two physical prototype restraint systems, namely an "advanced-belt only" design and an "advanced-belt and SCaRAB" design, were then tested in the final sled series. With the soft crash pulse, both advanced restraint systems were able to reduce all the injury measures below the IARVs for all four ATDs. Both advanced restraint systems also effectively reduced almost all the injury measures for all ATDs under the severe crash pulse, except for the THOR. The design with the advanced-belt and SCaRAB generally provided lower injury measures than those using the advanced belt-only design. This study highlighted the potential benefit of using advanced seatbelt and airbag systems for rear-seat occupant protection in frontal crashes.

Occupant responses in conventional and ABTS seats in high-speed rear sled tests

ABSTRACTObjective: This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats 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. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics.Results: Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats.Conclusions: Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.

Biomechanical and Scaling Basis for Frontal and Side Impact Injury Assessment Reference Values.

In 1983, General Motors Corporation (GM) petitioned the National Highway Traffic Safety Administration (NHTSA) to allow the use of the biofidelic Hybrid III midsize adult male dummy as an alternate test device for FMVSS 208 compliance testing of frontal impact, passive restraint systems. To support their petition, GM made public to the international automotive community the limit values that they imposed on the Hybrid III measurements, which were called Injury Assessment Reference Values (IARVs). During the past 20 years, these IARVs have been updated based on relevant biomechanical studies that have been published and scaled to provide IARVs for the Hybrid III and CRABI families of frontal impact dummies. Limit values have also been developed for the biofidelic side impact dummies, BioSID, ES-2 and SID-IIs. The purpose of the original publication was to provide in a single document: 1) a listing of the IARVs for measurements made with the Hybrid III and CRABI families of frontal impact dummies, and for the biofidelic side impact dummies, 2) the biomechanical and/or scaling bases for these IARVs, and 3) a comparison of IARVs and regulatory compliance limits and how they affect restraint design. The purpose for republication is to correct errors in the original publication and update the regulatory compliance limits.

Evaluation of driver lower extremity injuries in 16 oblique crashes with THOR

Injuries to the lower extremity (LE) continue to occur in frontal crashes despite increased attention on the vehicle structure and restraint design. This study focuses on thigh, leg, foot, and ankle injuries as well as occupant factors and intrusion levels. Sixteen vehicles, including three same types, with same moving deformable barriers of the same mass, velocity, and barrier face properties, and the same occupant Test Device for Human Occupant Restraint (THOR) 50th percentile adult male in the driver's seat were used to conduct oblique impact test. Data from the left (driver side) oblique crash tests conducted by National Highway Traffic Safety Administration (NHTSA) were used in this paper to analyse the detailed intrusion characteristics and the driver side THOR injuries from head to foot in these 16 tests. Different regions of the THOR dummy were analysed. Maximum values of all lower extremity injury criteria were obtained and analysed. Intrusion and lower extremity injuries correlation was found, knee airbag and lower extremity injury correlation was also analysed. The foot-well X and Y intrusions in the 16 tests rank from minimum 14 to maximum 309 mm and from −7 to 184 mm, independently. Sixty-nine per cent right knee displacement is greater than the left knee displacement. Thirty-one per cent knee displacement and 44% left upper tibia force of the 16 tests have values that exceed injury assessment reference values. Left upper tibia force was generally greater than other tibia forces. Half of the left upper tibia index (TI) and 37.5% of the right lower TI do not meet the standard value. The foot/ankle complex is generally at a higher risk than the other parts of the leg. Same vehicle reproducibility and injury were also analysed. Right knee displacement, left femur force, left upper tibia force, left upper TI, and left ankle rotation are the most critical injuries in the respective regions of the lower extremity. Intrusion may be more prominent in some frontal damage types than in others, but not the only reason for lower extremity injuries. Other factors that influence LE injuries are the position of driver foot, the geometry of the foot-well area, the direction of intrusion, the impact energy, and acceleration of the floor. Lower extremity is the most frequently injured body region with respect to more serious injuries in the analysed test data.