A method for generating case-specific vehicle models from a single-view vehicle image for accurate pedestrian injury reconstructions.

Developing vehicle finite element (FE) models that match real accident-involved vehicles is challenging. This is related to the intricate variety of geometric features and components. The current study proposes a novel method to efficiently and accurately generate case-specific buck models for car-to-pedestrian simulations. To achieve this, we implemented the vehicle side-view images to detect the horizontal position and roundness of two wheels to rectify distortions and deviations and then extracted the mid-section profiles for comparative calculations against baseline vehicle models to obtain the transformation matrices. Based on the generic buck model which consists of six key components and corresponding matrices, the case-specific buck model was generated semi-automatically based on the transformation metrics. Utilizing this image-based method, a total of 12 vehicle models representing four vehicle categories including family car (FCR), Roadster (RDS), small Sport Utility Vehicle (SUV), and large SUV were generated for car-to-pedestrian collision FE simulations in this study. The pedestrian head trajectories, total contact forces, head injury criterion (HIC), and brain injury criterion (BrIC) were analyzed comparatively. We found that, even within the same vehicle category and initial conditions, the variation in wrap around distance (WAD) spans 84-165 mm, in HIC ranges from 98 to 336, and in BrIC fluctuates between 1.25 and 1.46. These findings highlight the significant influence of vehicle frontal shape and underscore the necessity of using case-specific vehicle models in crash simulations. The proposed method provides a new approach for further vehicle structure optimization aiming at reducing pedestrian head injury and increasing traffic safety.

A multi-level analysis on the causes of train-pedestrian collisions in Southwest China 2011-2020.

Collisions between trains and pedestrians are the primary cause of railway casualties. However, there remains a lack of comprehensive understanding regarding the underlying causes of this phenomenon. This study employs a multi-level approach to investigate the factors associated with the occurrence and severity of train-pedestrian collisions. The investigation is based on 2160 independent cases that occurred in southwest China from 2011 to 2020. Multiple contributing factors related to the victim, train, track, and socio-economic status of the surrounding district were examined, utilizing information from various sources. At the county level, several risk factors were identified in predicting the occurrence rate. These factors include higher population density and a greater number of normal-speed stations. However, the presence of high-speed train stations did not exhibit any significant impact. Additionally, the study found that regulations pertaining to protective fences were highly effective in reducing the occurrence rate. Regarding the prediction of collision severity, certain factors were found to increase the death rate. These factors include young men as victims, engaging in lying down or crossing behaviors, higher train speeds, gentle downhill slopes, lower education levels, and a higher proportion of the labor force. These findings emphasize the necessity of adopting a comprehensive perspective when examining the causes of train-pedestrian collisions. Furthermore, it underscores the significance of considering the notable differences between rapidly developing countries such as China and developed countries. Based on our findings, we also provide corresponding policy suggestions.

The "mystery" of the train station: The importance of a forensic approach to a rare case of survival after a train-pedestrian collision.

In the early morning a 28-year-old man was found lying on the tracks of a railway station with head injuries and fractures of the cervical spine resulting in permanent quadriplegia. He was in a club about 1 km away until about 2 h earlier and did not have any recollection of what could have happened. Was he the victim of an assault, did he fall down or was he hit by a passing train? The solution to this "mystery" came from a forensic evaluation that included the forensic branches of pathology, chemistry, merceology and genetics as well as the scene evaluation. Through these different steps, the role of a railway collision in determining the injuries was ascertained and a possible dynamic was postulated. The presented case is an expression of the importance of the different forensic disciplines and the difficulties the forensic pathologist encounters when analysing such peculiar and rare cases.

Should anthropometric differences between the commonly used pedestrian computational biomechanics models and Chinese population be taken into account when predicting pedestrian head kinematics and injury in vehicle collisions in China?

Computational biomechanics models play a key role in predicting/evaluating pedestrian head kinematics and injury risk in car-to-pedestrian collisions. The human multibody models most commonly used in car-to-pedestrian collision reconstruction, such as pedestrian model by The Netherlands Organisation for Applied Scientific Research TNO, are built using the anthropometry of Western European population as defined in TNO (2013) human multibody model database. In this study, we investigate the effects of the anthropometric differences between the Western European and Chinese populations on the pedestrian head kinematics and injury responses predicted using multibody models. The comparison was conducted through car-to-pedestrian collision simulations using pedestrian multibody models representing anthropometric characteristics of Western European and Chinese populations, three typical vehicle shapes (sedan, SUV and minivan), five initial vehicle impact speeds (30, 35, 40, 45, 50 km/h), and six pedestrian walking postures. The results indicate that the change of pedestrian model anthropometry (from Western European to Chinese) exerts appreciable effects on both the predicted initial boundary conditions of the head-to-windscreen impact (in particular the head-to-windscreen impact angle) and the head injury indices in the impact with the road surface (secondary impact).

Characteristics of Train-Pedestrian Collisions in Southwest China, 2011-2020.

Although train-pedestrian collisions are the primary source of railway casualties, the characteristics of this phenomenon have not been fully investigated in China. This study examined such collisions in the Greater Sichuan-Chongqing area of China by conducting a thorough descriptive analysis of 2090 incident records from 2011 to 2020. The results showed that such collisions have declined gradually over the past decade, but the fatality rate remains high. We found that such collisions were more likely to happen to men, senior citizens and people crossing the tracks and that they occurred more frequently in the morning. While collision rates dropped in February, collisions were more likely to occur in December. In contrast to the situation in Western countries, weekends were not related to increased occurrence. The absence of a protective fence led to a higher collision rate, but level crossings are no longer a concern since most such structures in China have been rebuilt as overpasses. Mild slopes and extreme curvatures were also found to increase the occurrence of such collisions. Freight trains were most likely to be involved in train-pedestrian collisions, and collisions caused by high-speed trains were rare both absolutely and relatively. However, when collisions did occur, higher train speeds were linked with higher fatality rates. The findings suggest that patterns of train-pedestrian collisions in China differ from those in the Western world. This difference might be caused by differences in culture, geography, weather and railway development policies. Future research directions and possible preventive measures are also discussed.

How effective are pedestrian crash prevention systems in improving pedestrian safety? Harnessing large-scale experimental data.

Over the past few years, the number of fatalities and severe injuries of vulnerable road users, particularly pedestrians, has risen substantially. Clearly, the safe mobility of pedestrians is critical in our transportation system. Technology can help reduce vehicle-pedestrian crashes, fatalities, and injuries. Emerging technologies such as pedestrian crash prevention (PCP) systems utilized in on-road vehicles have the potential to mitigate pedestrian crash severity or prevent crashes. However, the reliability and effectiveness of these technologies have remained uncertain. This study contributes toward understanding the effectiveness of PCP systems utilized in on-road vehicles with a low level of automation by investigating two crossing and one longitudinal scenarios. The Insurance Institute for Highway Safety field test data from 2018 to 2021 is harnessed, where several on-road vehicles and their PCP systems are evaluated in terms of safety. The large-scale experimental dataset is comprised of 3095 tests of 91 vehicles with different sizes, makes, and models. The empirical results indicate that in hazardous pedestrian-vehicle conflict situations, the performance of PCP systems has been improved during recent years. The test data shows that some pedestrians were undetected in some tests, but on average, in 70% of the tests, the PCP systems avoided pedestrian crashes. However, for the occurred crashes, PCP systems, on average, were able to mitigate impact speeds of >50%. In real-life situations, this could translate to substantial reductions in injury and fatality risk. Through rigorous analysis, the associations of key factors in the studied scenarios and the performance of PCP systems are explored and discussed in this paper. The modeling results show that increasing the maximum deceleration rate of the PCP system and lower weight of vehicles can significantly improve the performance of the PCP system by decreasing the speed at impact with pedestrians. The average maximum deceleration utilized in PCP systems has been increased over time from 7.48 m/s2 in 2018 to 9.36 m/s2 in 2021. This can be one of the reasons behind the improvement of PCP systems during recent years.

Vulnerable road user safety evaluation using probe vehicle data with collision warning information.

Recently, connected vehicle (CV) and advanced driver assistance system (ADAS) technologies, including retrofit ADAS products, have been introduced in the real-world market. This study focuses on pedestrian collision warning (PCW) as an intensive function of the ADAS, which operates when a vehicle is at a collision risk with a vulnerable road user (VRU). Although several studies have been conducted on surrogate safety measures for crashes against VRUs, none of these studies used real-world CV data with collision warning information. Thus, the current study aims to i) develop a safety performance function (SPF) for crashes against VRUs at unsignalized intersections, where the PCW information was acquired using connected advanced probe vehicles (APVs), and ii) assess the effectiveness of a traffic-safety treatment implemented at an unsignalized intersection based on the developed SPF. In particular, this study proposes a two-step empirical Bayesian estimation based on the SPF model (2-step EB-SPF) to consider the issue regarding the limited number and vehicle types of APVs that can obtain PCW information. Based on the APV data, the vehicle-VRU crash-count negative binomial (NB) models were separately estimated using the actual PCW incidence rate and the EB estimate of PCW incidence rate, respectively. Although the actual PCW incidence rate was not statistically significant in the former model, the EB estimate of the PCW incidence rate was statistically significant and positively related to the crash count in the latter model. Moreover, a traffic-safety treatment was implemented at an unsignalized intersection and subsequently assessed as a case study based on the estimated 2-step EB-SPF model. Consequently, the model with the EB estimate of PCW incidence rate revealed that the vehicle-VRU crash risk was reduced by approximately 70%, and it was statistically significant at the 99% confidence level, which diminished the confidence interval in comparison to the model without the PCW incidence rate. Thus, the APV data including collision warning information can improve the estimation accuracy of determining the effect of the traffic-safety treatment, which can considerably contribute toward traffic safety assessment, especially for short after-treatment periods such as that prevailing in this case study.

Understanding Head Injury Risks During Car-to-Pedestrian Collisions Using Realistic Vehicle and Detailed Human Body Models.

Traumatic brain injury (TBI) is the leading cause of death and long-term disability in road traffic accidents (RTAs). Researchers have examined the effect of vehicle front shape and pedestrian body size on the risk of pedestrian head injury. On the other hand, the relationship between vehicle front shape parameters and pedestrian TBI risks involving a diverse population with varying body sizes has yet to be investigated. Thus, the purpose of this study was to comprehensively study the effect of vehicle front shape parameters and various pedestrian bodies ranging from 95th percentile male (AM95) to 6 years old (YO) child on the dynamic response of the head and the risk of TBIs during primary (vehicle) impact. At three different collision speeds (30, 40, and 50 km/h), a total of 36 car-to-pedestrian collisions (CPCs) were reconstructed using three different vehicle types (Subcompact passenger sedan, mid-sedan, and sports utility vehicle (SUV)) and four distinct THUMS pedestrian finite element (FE) models (AM50, AM95, AF05, and 6YO). We assessed skull stress and brain strains besides head linear and rotational kinematics. Our findings indicate that vehicle shape parameters especially bonnet leading edge height (BLEH), when being divided by the height of the Center of Gravity of the human body, correlated positively to head kinematics. The data from this study using realistic vehicle structures and detailed human body models showed that smaller BLEH/CG ratios reduced head injury criteria (HIC) and brain injury criteria (BrIC) values for the car center to mid-stance walking pedestrian impacts but with low-to-moderate R squared values between 0.2 to 0.5. Smaller BLEH/CG reduced head lateral bending velocities with R squared values of 0.57 to 0.63 for all impact velocities, and reduced HIC with R squared value of 0.62 for 50 km/h cases. In the future, simulations with realistic car structures and detailed human body models will be further used to simulate impacts at different locations and with various body shapes/postures.

Scope Assessment of Soft Tissue Injury within Polytrauma for Needs of Fortis System Injury Classification.

BACKGROUND: The paper points out the importance of quantifying the extent and nature of organ and tissue injury within the assessment of severity of damage to health caused by effect of blunt or combined force. OBJECTIVE: This study aims to determine the value of mechanical violence that caused the injury using the Fortis system based on the detected range of injured soft tissue and the localization of the sites affected by said violence. MATERIAL AND METHODS: In this experimental study the authors carried out measurements and calculations in 10 pedestrians, who died of polytrauma in an accident. The morphometric Ellipse v.2.0.7.1.software was used for the purpose (Vidito Kosice, Slovak Republic). RESULTS: The internal organ injuries were successfully evaluated in a planographic manner on serial sections with the following calculation of total extent of tissue damage (TETD). It turned out that if TETD is more than 40%, it will be possible to evaluate an injury as severe or life-threatening. CONCLUSION: The above classification and localization of pedestrian injuries facilitate calculations in simulation programs to determine how the movement of a pedestrian´s body during and after the collision occurred based on the unrepeatability of movement parameters; besides, contacts with a vehicle help determine the input data to calculate the collision. Based on the submitted case reports and performed measurements and calculations, the presented method of the extent classification of soft tissue damage is evaluated to be useful to standardize the injury parameters and assess polytrauma as a result of disproportionate force.

Representing two road traffic collisions in one Accimap: highlighting the importance of emergency response and enforcement in a low-income country.

Seemingly erratic pedestrian crossing has become a major source of vehicle-pedestrian collisions on highways in Bangladesh, and across other low- and middle-income countries (LMICs). In this article, we approach the challenge from a sociotechnical systems perspective by using the Accimap method to analyse a pair of time-separated yet interconnected road traffic collisions. The first event involved a truck colliding with a road divider; in the second, fatal incident, a bus hit a university student. The traditional-style investigation conducted immediately after the collision apportioned blame to end users, that is, drivers and pedestrian; however, application of sociotechnical systems thinking revealed the contribution from lack of emergency response and enforcement among many other important factors. Results and recommendations are discussed in terms of reducing the chance and severity of such collisions across LMICs, and in terms of the need to look beyond the end-user, a focus that remains dominant in such settings. Practitioner summary: This paper applies sociotechnical systems thinking to pedestrian safety in Bangladesh by analysing two inter-connected road traffic collisions using a single Accimap. The findings emphasise the importance of implementing road safety interventions that target all system levels, and draw attention to the importance of post-collision response in low-income settings. Abbreviation: BUET: Bangladesh University of Engineering and Technology.

A Computational Biomechanics Human Body Model Coupling Finite Element and Multibody Segments for Assessment of Head/Brain Injuries in Car-To-Pedestrian Collisions.

It has been challenging to efficiently and accurately reproduce pedestrian head/brain injury, which is one of the most important causes of pedestrian deaths in road traffic accidents, due to the limitations of existing pedestrian computational models, and the complexity of accidents. In this paper, a new coupled pedestrian computational biomechanics model (CPCBM) for head safety study is established via coupling two existing commercial pedestrian models. The head-neck complex of the CPCBM is from the Total Human Model for Safety (THUMS, Toyota Central R&D Laboratories, Nagakute, Japan) (Version 4.01) finite element model and the rest of the parts of the body are from the Netherlands Organisation for Applied Scientific Research (TNO, The Hague, The Netherlands) (Version 7.5) multibody model. The CPCBM was validated in terms of head kinematics and injury by reproducing three cadaveric tests published in the literature, and a correlation and analysis (CORA) objective rating tool was applied to evaluate the correlation of the related signals between the predictions using the CPCBM and the test results. The results show that the CPCBM head center of gravity (COG) trajectories in the impact direction (YOZ plane) strongly agree with the experimental results (CORA ratings: Y = 0.99 ± 0.01; Z = 0.98 ± 0.01); the head COG velocity with respect to the test vehicle correlates well with the test data (CORA ratings: 0.85 ± 0.05); however, the correlation of the acceleration is less strong (CORA ratings: 0.77 ± 0.06). No significant differences in the behavior in predicting the head kinematics and injuries of the tested subjects were observed between the TNO model and CPCBM. Furthermore, the application of the CPCBM leads to substantial reduction of the computation time cost in reproducing the pedestrian head tissue level injuries, compared to the full-scale finite element model, which suggests that the CPCBM could present an efficient tool for pedestrian brain-injury research.

Parameter sensitivity analysis of pedestrian head dynamic response and injuries based on coupling simulations.

There are a very limited number of reports studying on the dynamic response and injuries of pedestrian head in the scenarios with head hitting windshield. This study aims to investigate the significant factors that affect the dynamic response and injuries of pedestrian head through finite element-multi-body coupling simulations. Two finite element vehicle models and two multi-body pedestrian human models were used to build the coupling simulations. Orthogonal experimental design and analysis of variance were used for parameter combination and data analysis. This study demonstrated that the dynamic response of pedestrian head and HIC15 were strongly associated with collision speed and pedestrian orientation. Vehicle type had a significant influence on the dynamic response of pedestrian head and HIC15, while there was no significant relationship between the dynamic response of pedestrian head and HIC15 and the size of pedestrian human models. Collision speed, pedestrian orientation, and vehicle type should be prioritized over the other collision parameters in the study of head injury mechanism and reconstruction of vehicle-pedestrian collisions in the scenarios with head hitting windshield.

Fatal abdominal injuries in a bicycle-pedestrian collision - Reconstruction using multibody simulation.

Fatal bicycle-pedestrian collisions do not occur frequently and thus are rarely reported in literature. Pedestrians in bicycle-pedestrian accidents often sustain severe craniocerebral injuries caused by a collision induced fall with head impact on the road surface. We describe a case where a pedestrian crossing a road was hit by a bicycle. Hematomas of the left lower leg and of the left flank/abdomen were found to be caused by the primary impact. However, the fatal injuries were found to be contralateral with a rupture of the right renal pedicle, a rupture of the right lobe of the liver and a tear of the vena cava. Neither the bicycle impact nor a fall onto the road surface could cause these injuries. Multibody simulation (PC Crash 9.2) revealed entanglement between the bicyclist and the pedestrian followed by a contact interaction between the pedestrian laying on the road surface and the falling bicyclist. In forensic case work post-crash contact interactions between the bicyclist and the pedestrian should be considered as a potential source of severe injuries.

[Pedestrian head injury biomechanics and damage mechanism. Pedestrian protection automotive regulation assessment]. / Biomecánica y mecanismo de producción del traumatismo cráneo-encefálico en el peatón atropellado. Evaluación de la normativa actual en la automoción.

INTRODUCTION: Pedestrian-vehicle collisions are a leading cause of death among motor vehicle accidents. Recently, pedestrian injury research has been increased, mostly due to the implementation of European and Japanese regulations. This research presents an analysis of the main head injury vehicle sources and injury mechanisms observed in the field, posteriorly the data are compared with the current pedestrian regulations. METHODS: The analysis has been performed through an epidemiologic transversal and descriptive study, using the Pedestrian Crash Data Study (PCDS) involving 552 pedestrians, sustaining a total of 4.500 documented injuries. RESULTS: According to this research, the hood surface is responsible for only 15,1% of all the head injuries. On the other hand, the windshield glazing is responsible for 41,8%. In case of sedan vehicles the head impact location exceeds what is expected in the current regulation, and therefore no countermeasures are applied. From all the head injuries sustained by the pedestrians just 20% have the linear acceleration as isolated injury mechanism, 40% of the injuries are due to rotational acceleration. CONCLUSIONS: In this research, the importance of the rotational acceleration as injury mechanism, in case of pedestrian-vehicle collision is highlighted. In the current pedestrian regulation just the linear acceleration is addressed in the main injury criteria used for head injury prediction.

Exploration of Pedestrian Head Injuries-Collision Parameter Relationships through a Combination of Retrospective Analysis and Finite Element Method.

There are a very limited number of reports concerning the relationship between pedestrian head injuries and collision parameters through a combination of statistical analysis methods and finite element method (FEM). This study aims to explore the characteristics of pedestrian head injuries in car-pedestrian collisions at different parameters by using the two means above. A retrospective analysis of pedestrian head injuries was performed based on detailed investigation data of 61 car-pedestrian collision cases. The head damage assessment parameters (head injury criterion (HIC), peak stress on the skull, maximal principal strain for the brain) in car-pedestrian simulation experiments with four contact angles and three impact velocities were obtained by FEM. The characteristics of the pedestrian head injuries were discussed by comparing and analyzing the statistical analysis results and finite element analysis results. The statistical analysis results demonstrated a significant difference in skull fractures, contusion and laceration of brain and head injuries on the abbreviated injury scale (AIS)3+ was found at different velocities (p < 0.05) and angles (p < 0.05). The simulation results showed that, in pedestrian head-to-hood impacts, the values of head damage assessment parameters increased with impact velocities. At the same velocity, these values from the impact on the pedestrian's back were successively greater than on the front or the side. Furthermore, head injury reconstruction and prediction results of two selected cases were consistent with the real injuries. Overall, it was further spelled out that, for shorter stature pedestrians, increased head impact velocity results in greater head injury severity in car-pedestrian collision, especially in pedestrian head-to-hood impacts. Under a back impact, the head has also been found to be at greater damage risk for shorter stature pedestrians, which may have implications on automotive design and pedestrian protection research if prevention and treatment of these injuries is to be prioritized over head injuries under a front or side impact.

On the evidential value of a Messerer fracture sustained in a car-pedestrian traffic accident.

A pedestrian was killed in a road traffic accident by collision with a car coming from the right. The victim's right femur was observed to have sustained a wedge-shaped fracture with biconcave side edges (so-called Messerer fracture), with the apex of the wedge pointing in the direction opposite to the direction of travel of the car. The absence of skin or soft tissue injuries in the area of the fracture means that it is reasonable to assume that this 'reverse wedge fracture' is an indirect fracture. The mechanism by which characteristic wedge-shaped fractures are produced through compression along the longitudinal axis of the bone has long been known. When reconstructing the direction of travel of a car involved in a collision with a pedestrian, forensic pathologists should therefore be cautious of assessing Messerer fractures in isolation.

Injury pattern in lethal motorbikes-pedestrian collisions, in the area of Barcelona, Spain.

INTRODUCTION: There are several studies about M1 type vehicle-pedestrian collision injury pattern, and based on them, there has been several changes in automobiles for pedestrian protection. However, the lack of sufficient studies about injury pattern in motorbikes-pedestrian collisions leads to a lack of optimization design of these vehicles. The objective of this research is to study the injury pattern of pedestrians involved in collisions with motorized two-wheeled vehicles. METHODS: A retrospective descriptive study of pedestrian's deaths after collisions with motorcycles in an urban area, like Barcelona was performed. The cases were collected from the Forensic Pathology Service database of the Institute of Legal Medicine of Catalonia. The selected cases were categorized as pedestrian-motorcycle collision, between January 1st, 2005 and December 31st, 2014. Data were collected from the autopsy, medical, and police report. The collected information was then analyzed using Microsoft Excel statistical functions. RESULTS: Traumatic Brain Injury is the main cause of death in pedestrian hit by motorized two-wheeled vehicles (62.85%). The most frequent injury was the subarachnoid hemorrhage, in 71.4% of cases, followed by cerebral contusions and skull base fractures (65.7%). By contrast, pelvic fractures and tibia fractures only appeared in 28.6%. CONCLUSIONS: The study characterizes the injury pattern of pedestrians involved in a collision with motorized two-wheeled vehicles in an urban area, like Barcelona, which has been found to be different from other vehicle-pedestrian collisions, with a higher incidence of brain injuries and minor frequency of lower extremities fractures in pelvis, tibia and fibula.

Validation of pedestrian throw equations by video footage of real life pedestrian/vehicle collisions.

A total of 11 real life vehicle/pedestrian collisions in 2012-2014 were captured by CCTV cameras/car cameras in Hong Kong. Some of the footage was recorded in HD format at 30 frames per second, enabling accurate determinations of impact speeds with pedestrians, exact points of impacts and final rest positions of pedestrians as well as kinematics of the collisions. The calculated impact speeds from footage analysis were used to validate the published empirical and semi-empirical pedestrian throw equations. The applicability of these equations to collisions on sloped carriageways was discussed. The presented results, including 6 forward projection trajectory cases, enrich the existing limited real life data from footage analysis for further validation of the published methodologies.

The influence of vehicle front-end design on pedestrian ground impact.

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, 40km/h) and three pedestrian types (50th % male, 5th % female, and 6-year-old child) at six different initial stance configurations, stationary and walking at 1.4m/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.