A current assessment of the THOR 50M in rear impacts.

OBJECTIVE: This study presents a comparison of the Test Device for Human Occupant Restraint (THOR) 50M and Hybrid III (HIII) 50M anthropomorphic test device (ATD) geometries and rear impact head and neck biofidelity to each other and to postmortem human surrogate (PMHS) data to evaluate the usefulness of the THOR in rear impact testing. METHODS: Both ATDs were scanned in a seated position on a rigid bench seat. A series of rear impact sled tests with the rigid bench seat with no head restraint support were conducted with a HIII-50M at 16 and 24 kph. Tests at each speed were performed twice with the THOR-50M to allow an assessment of the repeatability of the THOR-50M. A comparison of the test results from THOR-50M testing were made to the results of a previous study that included PMHS. Rear impact sled tests with both ATDs in a modern seat were then conducted at 40 kph. RESULTS: The THOR-50M head was 48.4 mm rearward and 60.1 mm higher than the HIII-50M head when seated in the rigid bench seat. In the repeated rigid bench testing at 16 and 24 kph, the THOR-50M head longitudinal and vertical accelerations, upper neck moment, and overall kinematics showed good test-to-test repeatability. In the rigid bench tests, the THOR-50M neck experienced flexion prior to extension in the 16 kph tests, where the neck of the HIII only experienced extension. At 24 kph both ATDs only experienced extension. The THOR-50M head displaced more rearward at both test velocities. The rigid bench tests show that the THOR-50M neck allows for more extension motion or articulation than the HIII-50M neck. The rigid bench test also shows that the head longitudinal and vertical accelerations, angular head kinematics, and upper neck moments were reasonably comparable between the ATDs. The THOR-50M results were closer to the average of the PMHS results than the HIII-50-M results, with the exception of the upper neck. In the 40 kph tests, with a modern seat design, the THOR-50M resulted in more deformation of the seatback with greater head restraint loading than the HIII-50M. The THOR-50M head backset distance was less. CONCLUSION: This study provides insight into the differences and similarities between the THOR and the HIII-50M ATD geometries, instrumentation responses, and kinematics, as well as the repeatability of the THOR-50M in rear impacts testing. The overall geometries of the THOR-50M and the HIII-50M are similar. The seated head position of the THOR-50M is slightly further rearward and higher than the HIII-50M. The results indicate that the THOR-50M matches the PMHS results more closely than the HIII-50M and may have improved neck biofidelity in rear impact testing. The results indicate that the studied THOR-50M responses are repeatable within expected test-to-test variations in rear impacts. Early data suggest that the THOR-50M can be used in rear impact testing, though a more complete understanding of the THOR-50M differences to the HIII ATDs will allow for better correlation to the existing body of HIII rear impact testing.

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.

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.

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.

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.

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.

Seat integrated and conventional restraints: a study of crash injury/fatality rates in rollovers.

This study used police-reported motor vehicle crash data from eleven states to determine ejection, fatality, and fatal/serious injury risks for belted drivers in vehicles with conventional seatbelts compared to belted drivers in vehicles with seat integrated restraint systems (SIRS). Risks were compared for 11,159 belted drivers involved in single- or multiple-vehicle rollover crashes. Simple driver ejection (partial and complete), fatality, and injury rates were derived, and logistic regression analyses were used to determine relative contribution of factors (including event calendar year, vehicle age, driver age/gender/alcohol use) that significantly influence the likelihood of fatality and fatal/serious injury to belted drivers in rollovers. Results show no statistically significant difference in driver ejection, fatality, or fatal/serious injury rates between vehicles with conventional belts and vehicles with SIRS.