| 1. |
- Dean, Morgan E., et al.
(författare)
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Assessing the applicability of impact speed injury risk curves based on US data to defining safe speeds in the US and Sweden
- 2023
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Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Vision Zero is an approach to road safety that aims to eliminate all traffic-induced fatalities and lifelong injuries. To reach this goal, a multi-faceted safe system approach must be implemented to anticipate and minimize the risk associated with human mistakes. One aspect of a safe system is choosing speed limits that keep occupants within human biomechanical limits in a crash scenario. The objective of this study was to relate impact speed and maximum delta-v to risk of passenger vehicle (passenger cars and light trucks and vans) occupants sustaining a moderate to fatal injury (MAIS2+F) in three crash modes: head-on vehicle-vehicle, frontal vehicle–barrier, and front-to-side vehicle-vehicle crashes. Data was extracted from the Crash Investigation Sampling System, and logistic regression was used to construct the injury prediction models. Impact speed was a statistically significant predictor in head-on crashes, but was not a statistically significant predictor in vehicle-barrier or front–to–side crashes. Maximum delta-v was a statistically significant predictor in all three crash modes. A head-on impact speed of 62 km/h yielded 50% (±27%) risk of moderate to fatal injury for occupants at least 65 years old. A head-on impact speed of 82 km/h yielded 50% (±31%) risk of moderate to fatal injury for occupants younger than 65 years. Compared to the impact speeds, the maximum delta-v values yielding the same level of risk were lower within the head-on crash population. A head-on delta-v of 40 km/h yielded 50% (±21%) risk of moderate to fatal injury for occupants at least 65 years old. A head-on delta-v of 65 km/h yielded 50% (±33%) risk of moderate to fatal injury for occupants younger than 65 years. A maximum delta–v value of approximately 30 km/h yielded 50% (±42%) risk of MAIS2+F injury for passenger car occupants in vehicle-vehicle front-to-side crashes. A maximum delta–v value of approximately 44 km/h yielded 50% (±24%) risk of MAIS2+F injury for light truck and van occupants, respectively, in vehicle-vehicle front-to-side crashes.
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| 2. |
- Meng, Shiyang, et al.
(författare)
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Craniofacial Injuries for Helmeted and Unhelmeted Bicyclists in Germany
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 105-112
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Konferensbidrag (refereegranskat)abstract
- Current bicycle helmet standards require impact testing mostly covering cranial or skull vault. Bicyclists are exposed to impacts to the face causing facial and basilar skull fractures, and soft tissue injuries, in addition to traumatic brain injuries. We aim to describe patterns and frequencies of craniofacial injuries grouped by anatomical and injury sites to inform new test method development in future bicycle helmet standards and subsequently promote protective designs. We analysed fully reconstructed crashes involving a bicycle from the German In-Depth Accident Study (GIDAS), crash years 2010-2022. The type and location of an injury was determined through the Abbreviated Injury Scale (2015 version), a GIDAS-own variable, and free-text information. We found that a substantial portion of craniofacial injuries were to the face for both helmeted and unhelmeted bicyclists. Facial injuries shifted from the upper face to the mid- and lower face when a helmet was worn. We identified the mid-face as the most prominent region for improving bicycle helmet safety. Hence, a new test method with an extended test area covering mid- and lower face is recommended and injury risk to commonly fractured facial bones should be assessed in future standards. Protective designs appear technically feasible: A visor in connection with a chin guard, or novel concepts using inflatable technology, can improve bicycle helmet designs for facial impact protection and could be assessed in future standards.
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| 3. |
- Meng, Shiyang, et al.
(författare)
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Evaluation of full-face, open-face, and airbag-equipped helmets for facial impact protection
- 2023
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Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 191
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Two-wheeler riders frequently sustain injuries to the head and face in real-world crashes, including traumatic brain injury, basilar skull fracture, and facial fracture. Different types of helmets exist today, which are recognized as preventing head injuries in general; however, their efficacy and limitations in facial impact protection are underexplored. Biofidelic surrogate test devices and assessment criteria are lacking in current helmet standards. This study addresses these gaps by applying a new, more biofidelic test method to evaluate conventional full-face helmets and a novel airbag-equipped helmet design. Ultimately, this study aims to contribute to better helmet design and testing standards. Methods: Facial impact tests at two locations, mid-face and lower face, were conducted with a complete THOR dummy. Forces applied to the face and at the junction of the head and neck were measured. Brain strain was predicted by a finite element head model taking both linear and rotational head kinematics as input. Four helmet types were evaluated: full-face motorcycle and bike helmets, a novel design called a face airbag (an inflatable structure integrated into an open-face motorcycle helmet), and an open-face motorcycle helmet. The unpaired, two-sided student's t-test was performed between the open-face helmet and the others, which featured face-protective designs. Results: A substantial reduction in brain strain and facial forces was found with the full-face motorcycle helmet and face airbag. Upper neck tensile forces increased slightly with both full-face motorcycle (14.4%, p >.05) and bike helmets (21.7%, p =.039). The full-face bike helmet reduced the brain strain and facial forces for lower-face impacts, but not for mid-face impacts. The motorcycle helmet reduced mid-face impact forces while slightly increasing forces in the lower face. Significance of results: The chin guards of full-face helmets and the face airbag protect by reducing facial load and brain strain for lower face impact; however, the full-face helmets’ influence on neck tension and increased risk for basilar skull fracture need further investigation. The motorcycle helmet's visor re-directed mid-face impact forces to the forehead and lower face via the helmet's upper rim and chin guard: a thus-far undescribed protective mechanism. Given the significance of the visor for facial protection, an impact test procedure should be included in helmet standards, and the use of helmet visors promoted. A simplified, yet biofidelic, facial impact test method should be included in future helmet standards to ensure a minimum level of protection performance.
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| 4. |
- Mishra, Ekant, et al.
(författare)
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Repositioning forward-leaning passengers by seatbelt pre-pretensioning
- 2023
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Ingår i: Traffic Injury Prevention. - 1538-957X .- 1538-9588. ; 24:8, s. 716-721
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The study determined the seatbelt pre-pretensioner force needed and the time required to reposition average male front-seat passengers from forward-leaning to upright using finite element simulations of the Active SAFER Human Body Model (Active SHBM). Methods: The Active SHBM was positioned in an initial forward-leaning position (29° forward from upright) on a deformable vehicle seat. A pre-pretensioner was modeled as a pre-loaded spring and its ability to reposition the forward-leaning Active SHBM to an upright position was simulated for twenty-four different pre-crash conditions. Four parameters were varied: (1) Automated Emergency Braking (AEB) active with 11 m/s2 or no AEB, (2) type of seatbelt system: Belt-In-Seat or B-pillar, (3) pre-pretensioner activation time (200 ms before, 100 ms before, or at the same time as AEB ramp-up), and (4) pre-pretensioner force (200 N, 300 N, 400 N, 600 N). The first thoracic vertebra fore-aft (T1 X) trajectories were compared against a reference upright position to determine the force and time needed to reposition and the effectiveness of repositioning in the different conditions. Results: The lowest force enabling repositioning in all simulations was 400 N (no AEB, Belt-In-Seat). It took about 350 ms. In the presence of AEB, activating the pre-pretensioner 200 ms before AEB and using 600 N pre-pretensioner force was needed for repositioning (taking 200 ms with Belt-In-Seat and 260 ms with B-pillar installations). Repositioning was faster and thus more effective with the Belt-In-Seat seatbelt in all simulations. Conclusions: All four parameters (presence of AEB, type of seatbelt system, pre-pretensioner activation time and force) affected the repositioning ability and time required. Far from all combinations repositioned a forward-leaning average male occupant model, but those found to be effective and fast appear as a feasible option for vehicle safety systems to reposition out-of-position occupants during pre-crash events.
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| 5. |
- Rizzi, Matteo, 1979, et al.
(författare)
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PROPOSED SPEED LIMITS FOR THE 2030 MOTOR VEHICLE
- 2023
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Ingår i: 27th ESV Conference Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Vision Zero builds on the aspiration to keep kinetic energy below human tolerance to prevent fatalities and serious injuries. In this work, a Swedish expert group within the SAFER arena estimated the maximum safe speed limits for the 2030 motor vehicle based on the boundary conditions of vehicles, road infrastructure and human crash tolerance to achieve close to zero road fatalities and serious injuries. The present work was based on expert consensus, rather than a retrospective quantitative analysis of crash data. Different load cases were discussed separately, with the involvement of a passenger car being the common denominator. The passenger car and its collision partner were assumed to be of model year 2030, thus reflecting the base safety level of the Swedish car fleet by approximately 2050. The boundary conditions were set based on pre-crash autonomous braking ability and the maximum acceptable impact speeds that would result in a very low risk of death or serious injury among the car occupants and the car’s collision partner. In the case of car to pedestrian impacts, the acceptable impact speed was set to zero, as any impact with pedestrians can lead to serious injuries as a result of ground impacts. It was expected that the responsibility to comply with speed limits will move from the driver to the car itself, and that travel speeds will be autonomously reduced when low road friction, sight obstructions, and other challenges in the traffic environment are detected. This function was expected to be non-overridable. Lateral control was also expected to be further enhanced with lane support technologies, although it was assumed that it will be still possible to override such technologies. Over time, increased performance of vehicle safety technologies will likely be able to prevent an increasingly large proportion of crashes in all load cases. However, in line with Vision Zero design principles, human crash tolerance will always be the ultimate boundary condition to guarantee a safe outcome in a crash. As a result, the recommended maximum travel speeds in the road transport system containing motor vehicles only of model year 2030 and beyond are: Rizzi 1 5-7 km/h in pedestrian priority areas, 40 km/h in mixed traffic urban areas, if there are no obstructed sensor sightlines, e.g. due to parked vehicles along the sidewalk, 50 to 80 km/h on roads without mid- and roadside barriers, 100+ km/h on roads with continuous mid- and roadside barriers, 40 to 60 km/h in intersections, depending on vehicle mass differences. The results from this work can be used to inform the development and amendment of transport planning guidelines when moving away from the economical paradigm into Safe System boundary conditions in the setting of speed limits.
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