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Pedestrians suffer significant injuries from ground contact, but attempts to reduce them have been limited. A recent study using multi-body simulations showed ground contact injury may be improved by controlling vehicle braking. The aim of the study is to assesses whether controlled braking would be beneficial in real-world collisions. PC-Crash was used to reconstruct 150 freely available real-world vehicle pedestrian video collisions. Pairwise comparison of actual versus controlled braking was then performed for each case. Pedestrian injury evaluation metrics included head injury criterion HIC15 and pelvis contact force, and another metric named separation distance between the vehicle and pedestrian at the instant of ground contact was used to test the feasibility of external airbags for mitigating ground contact. Substantial head and pelvis injury reductions may be possible through the application of controlled braking. Full vehicle braking after first vehicle-pedestrian contact has little influence on overall pedestrian injury outcome. In controlled braking, an external semi-elliptic airbag with a range 2 m can prevent 83.1% ground contact (only 46.6% in actual cases) and there is a high probability (50%) that the available space to control braking is limited if the vehicle deviates from its original lane. Various kinematic explanations are presented, consistent with the principle that the vertical component of the impact on the ground can be reduced by controlling the vehicle braking. Despite the variation in real-world pedestrian collisions, controlled braking may generally provide a benefit for ground contact injuries. [ABSTRACT FROM AUTHOR]

The problem of injury protection for pedestrian is a research hot spot in traffic safety, and simulations are important research tools. In the process of design of simulation experiments, pedestrian gaits become more and more important. Hence in the research three pedestrian gait serials (walking, running and emergency) were found through observing and reconstructing 150 vehicle-pedestrian collision videos. Further studies had found that pedestrian speed and pedestrian injury are different among the three gait serials and there is significant difference between the Pedestrian Speed Before the Collision (PSBC) and the Pedestrian Speed at the Instant of the Collision (PSIC) in the same gait serial; for the emergency gait serial, there is significant difference between the estimated and reconstructed pedestrian heights; and there is high relevance between angles of the left extremities and the corresponding right extremities. Furthermore, based on results observed from the 150 videos and those existing research results, ten pedestrian gaits in each gait serial were proposed, simulation results shown that the pedestrian injury in different gait serial and in different gaits in the same gait serial are all different. The observed pedestrian gaits will help us to design a more objective simulation experiments in the future in analyzing pedestrian injury. [ABSTRACT FROM AUTHOR]

Methods to estimate the pre-impact pedestrian speed from limited post-accident measurements are required both for biomechanics research and for legal applications following vehicle–pedestrian collisions, but none is currently available. Such a method is presented in this paper. A constant-inertial-property pedestrian model based on the conservation of momentum is first shown to predict satisfactorily the transverse offset of a pedestrian between the primary and secondary impacts in wrap-trajectory vehicle–pedestrian collisions and is then used in a Monte Carlo environment to predict the pedestrian pre-impact speed distribution utilizing an estimate of the vehicle speed based on the pedestrian projection distance, the ratio of the longitudinal offset to the transverse offset for the pedestrian primary and secondary contact locations on the vehicle (indicated by the primary and secondary vehicle damage locations) and, where available, information on the pedestrian gait stance at impact (derived from the injury location on the head). Separate analysis of recently published Fourier relationships between the transverse offset and the contact location on the head derived from modelling with Mathematical Dynamic Models (MADYMO) software is used to show that the gait stance is related to the location on the head of head injuries from the vehicle contact, and that contact locations significantly anterior or posterior of the coronal plane are predominant. Results from the constant-inertial-property pedestrian model show that significant differences occur between the ratio of the transverse offset to the longitudinal offset with the struck leg leading and the corresponding ratio with the struck leg lagging. The special case of nominally zero transverse offset between the primary and secondary damage locations from the contacts of the pedestrian with the vehicle is considered, and pedestrian speed confidence limits for accident reconstruction purposes are provided. Regression equations relating the pedestrian speed to the pedestrian projection distance and the ratio of the transverse offset to the longitudinal offset of the damage location on the vehicle are presented. These provide the first means to predict the pedestrian speed from limited post-accident damage locations on the vehicle and the pedestrian projection distance. [ABSTRACT FROM AUTHOR]

• We are the first to evaluate the potential protective effect of controlling vehicle braking during vehicle pedestrian impacts. • The severity of contact of the head and pelvis with the ground can frequently be reduced. • Controlled braking increases the proximity of the vehicle to the pedestrian at the instant of ground contact. • The increased stopping distance associated with controlled braking mostly poses no conflict with the available free space in front of the vehicle. Protecting struck pedestrians during the ground contact phase has been a challenge for decades. Recent studies have shown how ground related injury is influenced by pedestrian kinematics. In this paper we further developed this approach by assessing the potential of controlling vehicle braking to reduce pedestrian ground contact injuries. Applying a recently proposed Simulation Test Sample, a series of simulations were run using the MADYMO software environment. The approach considered 6 vehicle shapes, 4 pedestrian models, 3 impact velocities and 2 pedestrian gaits and each case was considered with two different vehicle braking approaches. The first was full braking, while the second applied controlled braking, for which a strategy based on pedestrian kinematics was applied. The effect of vehicle braking was evaluated using the Weighted Injury Cost (WIC) of overall pedestrian injuries and the pedestrian-ground impact velocity change. The proximity of the vehicle and pedestrian at the instant of ground contact was also evaluated to assess the potential of future vehicle based intervention methods to cushion the ground contact. Finally real-world videos of pedestrian collisions were analyzed to estimate the available free vehicle stopping distances. Results showed substantial median reductions in WIC and head impact velocity for all vehicle shapes except the Van. The proximity of the pedestrian to the vehicle front at the instant of ground contact under controlled braking is less than 1.5 m in most cases, and the required stopping distance for the vehicle under controlled braking was within the available stopping distance estimated from the video footage in about 74% of cases. It is concluded that controlled braking has significant potential to reduce the overall burden of pedestrian ground contact injuries, but future efforts are required to establish an optimized braking strategy as well as a means to handle those cases where controlled braking is not beneficial or even harmful. [ABSTRACT FROM AUTHOR]

Comments on the increased use of sport utility vehicles and on the ageing population. Concern of the World Health Organization about the probability of more severe injuries and deaths in traffic accidents involving SUVs and elderly pedestrians; How pedestrian safety can be achieved, including improved vehicle design; Indication that vehicle mass is a minor factor in vehicle-pedestrian collisions and increased mortality and morbidity results from the geometry of the SUV front-end structure; Suggestion that crash investigation should identify SUVs in accident statistics and that activists in the health professions should pressure governments to require effective safety strategies; Effort of the Irish Medical Organisation to make the public aware of the increased risk to pedestrians from SUVs.

The effect of pedestrian gait on lower limb kinematics and injuries has not been analyzed. The purpose of this paper was therefore to investigate the effect of pedestrian gait on kinematics and injury risk to the lower limbs using the Total Human Model for Safety adult male pedestrian model together with FE models of vehicle front structures. The modeling results indicate that the tibia and femur cortical bone von-Mises stress and the lateral knee bending angle of an adult pedestrian are strongly dependent on the gait stance when struck by both a sedan car and an SUV at 40 km/h. The gait analysis shows that generally the leg of an adult pedestrian has lower injury risk when the knee is flexed and linear regressions show high negative correlation between knee flexion angle during impact and knee lateral bending angle and also high negative correlation between lower leg axial rotation during impact and knee lateral bending angle. Furthermore, in some gait stances a self-contact between the legs occurs, and the peak bones stresses and knee shearing displacement in the leg are then increased. Assessment of pedestrian lower limb injury should take account of these gait stance effects. [ABSTRACT FROM AUTHOR]

• A detailed analysis of the occurrence of pedestrian head injury types categorised separately into skull and brain injuries. • GIDAS accident data, Spearman's rank correlation coefficient and logistic regression model are employed. • Interrelationship between different head injury types was investigated. • Influences of impact speed, pedestrian age and car front shape on different kinds of pedestrian head injuries were studied. Head injury is one of the most common injury types in vehicle-to-pedestrian collisions, which leads to death and long-term disabilities. However, detailed analysis of pedestrian head injuries in real world collisions is scarce. Thus the current study used two samples of 120 cases and 184 cases extracted from 1060 pedestrian collision cases captured during 2000–2015 from the GIDAS (German In-Depth-Accident Study) database to investigate the detailed characteristics of AIS2+ pedestrian head injuries. Firstly, the interrelationship between different head injury types (skull fracture, focal brain injury, concussion and diffuse axonal injury (DAI)) was analysed using the sample of 120 cases which each had at least one AIS2+ head injury. Then the influences of impact speed, pedestrian age and car front shape parameters on the injury risk of skull fracture, focal brain injury and concussion were assessed using the logistic regression method, based on the sample of 184 AIS1+ cases where the primary head contact location was within the windscreen glass area. The results show that: skull fractures and focal brain injuries dominate for AIS3+ head injuries and are generally associated with each other; concussion is the most important injury type for AIS2 head injuries and usually occurs in isolation. Further, for head impacts to the windscreen glass area a higher bonnet leading edge helps to reduce concussion odds, and none of the selected car front shape parameters are significant for the odds of skull fracture and focal brain injury, and vehicle impact speed and pedestrian age are insignificant for concussion. These detailed characteristics of pedestrian head injuries provide a basis for future pedestrian head injury prevention strategies with skull fractures and focal brain injuries being the most important injuries to address. [ABSTRACT FROM AUTHOR]

Most pedestrians struck by vehicles receive injuries from contact with the vehicle and also from the subsequent ground contact. However, ground related pedestrian injuries have received little focus. This paper uses 1221 German pedestrian collision cases occurring between 2000 and 2015 to assess the distribution and risk factors for pedestrian ground related injuries. Results show that for MAIS 2, the ground accounted for 24% of cases, for MAIS 3 the ground accounted for 20% of cases and for MAIS 4–5, the ground accounted for 14% of cases. There were no AIS 6 ground related injuries, though there were several fatal cases where the ground was coded as the most serious injury. The head, thorax and spine dominate AIS 4–5 ground contact injuries. Vehicle impact speeds were higher for ground related AIS 4–5 compared to AIS 2 injury cases and the average impact speed for ground related injuries to the upper and lower extremities was lower than for body regions like head, thorax and spine. There was a significant age effect on pedestrian ground related injury outcome, with older pedestrians suffering more severe injuries and the median age for thorax injuries was higher than for all other body regions. There was no significant difference in the proportions of AIS 2+ head injuries produced by ground contact for more recent vehicles (model year since 2005) compared to older vehicles (model year before 2005). However, logistic regression analysis showed that the normalised bonnet leading-edge height is a risk factor for adult pedestrian AIS2+ ground related head injuries, and this provides empirical support for recent computational modelling predictions which implied a relationship between vehicle shape and pedestrian ground contact injuries. Considering the potential benefits of preventing pedestrian ground contact, for collisions below 40 km/h two thirds of the injury costs would be eliminated if ground contact could be prevented, and even higher benefits are likely at lower speeds (20 and 30 km/h). These data demonstrate the importance of ground related pedestrian injuries and show that vehicle shape influences pedestrian injury outcome in ground contact. The data therefore provides significant motivation for countermeasures to prevent or moderate pedestrian ground related injuries. [ABSTRACT FROM AUTHOR]

Quantified relationships between passenger car front shape and pedestrian injury risk derived from accident data are sparse, especially considering the significant recent changes in car front design. The purpose of this paper is therefore to investigate the detailed effects of passenger car front shape on injury risk to a pedestrian’s head, thorax, pelvis and leg in the event of a vehicle pedestrian impact. Firstly, an accident sample of 594 pedestrian cases captured during 2000–2015 from the German In-Depth Accident Study (GIDAS) database was employed. Multicollinearity diagnostic statistics were then used to detect multicollinearity between the predictors. Following this, logistic regression was applied to quantify the effects of passenger car front shape on injury risks while controlling for impact speed and pedestrian age. Results indicate that the bumper lower depth (BLD), bumper lower height (BLH), bumper upper height (BUH) and normalised bumper lower/upper height (NBLH/NBUH) are statistically significant for AIS2+ leg injury risk. The normalised bonnet leading edge height (NBLEH) has a statistically significant influence on AIS2+ femur/pelvis injury occurrence. The passenger car front shape did not show statistical significance for AIS3+ thorax and head injuries. The impact speed and pedestrian age are generally significant factors influencing AIS2+ leg and pelvis injuries, and AIS3+ thorax and head injuries. However, when head impacts are fixed on the central windscreen region both pedestrian age and impact speed are not statistically significant for AIS3+ head injury. For quantified effects, when controlling for speed, age and BUH, an average 7% and 6% increase in AIS2+ leg injury odds was observed for every 1 cm increase in BLD and BLH respectively; 1 cm increase in BUH results in a 7% decrease in AIS2+ leg injury odds when the BLD or BLH are fixed respectively (again controlling for impact speed and pedestrian age); the average AIS2+ femur/pelvis injury odds increase by 74% for a 10% increase in NBLEH. These findings suggest that passenger car bumpers should support the lower leg with a low and flat lower bumper and even contact up to the femur area with a high upper bumper which extends above the knee to protect the pedestrian’s leg. A low passenger car bonnet leading edge helps to reduce femur/pelvis injury risk. The passenger car front shape parameters are less influential than impact speed and pedestrian age for pedestrian injury risk. [ABSTRACT FROM AUTHOR]

Motivated by the thousands of pedestrians killed each year in train impacts, this paper investigates the life-saving capability of four high-level locomotive bumper concepts. The head motions produced by the four concepts are modeled as one or two square acceleration pulses and are analyzed using the Head Injury Criterion (HIC). Surprisingly, the analyses show that all four concepts can achieve HIC values of less than 200 for an impact with a locomotive traveling at 100 km/h. Two of the concepts eject the pedestrian trackside with at a velocity of roughly 40 km/h and the risk of ground-impact injury is discussed in the context of related automobile accident data. The computed bumper lengths are a fraction of the overall length of a locomotive and are thus feasible for practical implementation. One concept involves an oblique impact and the potential for rotational head injury is analyzed. This basic feasibility research motivates future investigations into the detailed design of bumper shapes, multi-body pedestrian simulations, and finite-element injury models. [ABSTRACT FROM AUTHOR]

Accident data have shown that in pedestrian accidents with high-fronted vehicles (SUVs and vans) the risk of pedestrian head injuries from the contact with the ground is higher than with low-fronted vehicles (passenger cars). However, the reasons for this remain poorly understood. This paper addresses this question using multibody modelling to investigate the influence of vehicle front height and shape in pedestrian accidents on the mechanism of impact with the ground and on head ground impact speed. To this end, a set of 648 pedestrian/vehicle crash simulations was carried out using the MADYMO multibody simulation software. Impacts were simulated with six vehicle types at three impact speeds (20, 30, 40 km/h) and three pedestrian types (50th % male, 5th % female, and 6-year-old child) at six different initial stance configurations, stationary and walking at 1.4 m/s. Six different ground impact mechanisms, distinguished from each other by the manner in which the pedestrian impacted the ground, were identified. These configurations have statistically distinct and considerably different distributions of head–ground impact speeds. Pedestrian initial stance configuration (gait and walking speed) introduced a high variability to the head–ground impact speed. Nonetheless, the head–ground impact speed varied significantly between the different ground impact mechanisms identified and the distribution of impact mechanisms was strongly associated with vehicle type. In general, impact mechanisms for adults resulting in a head-first contact with the ground were more severe with high fronted vehicles compared to low fronted vehicles, though there is a speed dependency to these findings. With high fronted vehicles (SUVs and vans) the pedestrian was mainly pushed forward and for children this resulted in high head ground contact speeds. [ABSTRACT FROM AUTHOR]

• This paper presents the first detailed assessment of the capacity of the MADYMO pedestrian model to replicate ground contact. • Sensitivity studies showed substantial influences of the vehicle-pedestrian contact characteristic on the ground contact kinematics. • The predictive capacity of the MADYMO pedestrian model for ground contact injury predictions needs to be improved. Pedestrian injuries occur in both the primary vehicle contact and the subsequent ground contact. Currently, no ground contact countermeasures have been implemented and no pedestrian model has been validated for ground contact, though this is needed for developing future ground contact injury countermeasures. In this paper, we assess the predictive capacity of the MADYMO ellipsoid pedestrian model in reconstructing six recent pedestrian cadaver ground contact experiments. Whole-body kinematics as well as vehicle and ground contact related a HIC (approximate HIC) and BrIC scores were evaluated. Reasonable results were generally achieved for the timings of the principal collision events, and for the overall ground contact mechanisms. However, the resulting head injury predictions based on the ground contact HIC and BrIC scores showed limited capacity of the model to replicate individual experiments. Sensitivity studies showed substantial influences of the vehicle-pedestrian contact characteristic and certain initial pedestrian joint angles on the subsequent ground contact kinematics and injury predictions. Further work is needed to improve the predictive capacity of the MADYMO pedestrian model for ground contact injury predictions. [ABSTRACT FROM AUTHOR]