Zhiyong Yin

Investigation of 184 passenger car–pedestrian accidents

In China, pedestrians were the most common and the most vulnerable of road users, meaning pedestrians were involved in vehicle-pedestrian accidents more frequently. Little attention has been paid to the investigation of such accidents. One surveying group was built to randomly collect vehicle-pedestrian accidents and analyse these accidents from the vehicle–pedestrian crash characteristics and the relationships between the pedestrian injury outcome and the impact speed. 184 pedestrians were injured and killed in these investigated passenger-car-pedestrian accidents. Among the 184 pedestrians involved in these accidents, 151 were crossing road arbitrarily (82.1%). There were only 17 accidents where the pavement and guardrail satisfied the safety standard. The males were the majority of the casualties (64.7%). Pedestrian injury localisations in head, extremities, chest and torso accounted for 68.5%, 68.5%, 24.5% and 15.8%, respectively. Of the fatalities, 71.4% resulted from brain injury. The injury outcome in elderly pedestrians was more severe and the head severe injury proportion in children was more than that of an adult. Multiple injuries were common in pedestrians. The pedestrian injury outcome was relative to the impact speed, i.e. faster the impact speed, higher was the pedestrians Injury Severity Score (ISS). There were no fatalities under the impact speed of 30 km/h and there were 4.4% of fatalities at the impact speed of 30∼39 km/h. When the impact speed was above 80 km/h, the pedestrians were severely injured or even killed.

Comparison of injuries sustained by drivers and pillion passengers in fatal head-on motorcycle collision accidents

This study aimed to compare injuries sustained by motorcycle drivers with those sustained by pillion passengers in fatal head-on motorcycle collision accidents. We examined 84 cases of fatal head-on motorcycle collision accidents, causing 79 deaths of drivers and 19 deaths of pillion passengers, using medical and medico-legal examination records. The distribution of superficial injuries, characteristic injuries, injury severity as well as fatal causes was evaluated and compared using χ(2) tests. The results revealed a significant difference in the distribution of superficial injuries between drivers and passengers. The proportions of injuries in the hand and perineum regions were significantly higher in drivers than passengers. Some characteristic superficial injuries on the palms, chest, abdomen as well as the perineum areas were observed in drivers, while none of these characteristic injuries were observed in pillion passengers. Drivers were found to have suffered more severe chest and abdomen injuries than passengers. In addition, there was a higher incidence of fatalities involving run-over injuries for drivers compared with pillion passengers. The proportion of fatal injuries related to tumbling was higher for passengers than for drivers. Overall, our results revealed a difference in injury severity, superficial injury distribution and characteristic injuries between drivers and passengers. Few characteristic injuries were found in pillion passengers. These findings could help to guide medico-legal examinations, particularly in identifying drivers among victims involved in traffic accidents.

An Investigation on the Head Injuries of Adult Pedestrians by Passenger Cars in China

Objective: To investigate the relative likelihood of pedestrian head injuries based on person, vehicular, and environmental factors in China. Methods: A team was established to collect passenger car–pedestrian accident cases occurring between 2006 and 2011 in Beijing, Shanxi Province, and Chongqing, China. Some key variables for person-, vehicle-, and environment-related factors on head injuries were analyzed using multivariate logistic regression analysis to determine relative risk/likelihood. Pedestrians were classified according to injury outcome and age. Pedestrian head injuries were scored using the Abbreviated Injury Scale (AIS). Results: A total of 285 vehicle–pedestrian crashes were collected and analyzed: 30 in Beijing, 20 in Shanxi Province, and 235 in Chongqing. The distribution in age and road type by study location differed. The injury outcome, head injury severity, and head contact site were different among 4 age groups. The variables including head contact site and impact speed were the common determinants for head injury severity. A higher pedestrian fatality risk was associated with age over 46, impact speeds over 40 km/h, and higher likelihoods of the victims head striking the windscreen frame/A pillar and of the victim sustaining a head injury. Similarly, a higher risk of head injury was associated with being female, age over 60, impact speeds over 40 km/h, and a likelihood of the victims head striking the vehicle rather than the ground. Impact speeds of over 40 km/h and head contact site on windscreen frame/A pillar retained a strong association with severe head injury (AIS 5–6) rate. Conclusions: Pedestrian age, vehicle impact speed, and head contact site were common pertinent factors for the risk of pedestrian head injury and the risk of death. Further studies would be valuable to fully characterize vehicle–pedestrian crashes in China and to develop targeted injury prevention strategies based on surveillance results. Supplemental materials are available for this article. Go to the publishers online edition of Traffic Injury Prevention to view the supplemental file.

Material Properties and Constitutive Modeling of Infant Porcine Cerebellum Tissue in Tension at High Strain Rate

Background The mechanical characterization of infant porcine cerebellum tissue in tension at high strain rate is crucial for modeling traumatic cerebellum injury, which is in turn helpful for understanding the biomechanics of such injuries suffered in traffic accidents. Material and Method In this study, the infant porcine cerebellum tissue was given three loading velocities, ie, 2s-1, 20s-1 and 100s-1 with up to 30% strain to investigate the tensile properties. At least six tensile tests for each strain rate were validly performed. Fung, Gent, Ogden and exponential models were applied to fit the constitutive equations, so as to obtain material parameters from the experimental data. Results The Lagrange stress of infant porcine cerebellum tissue in tension appeared to be no more than 3000Pa at each loading velocity. More specifically, the Lagrange stress at 30% strain was (393.7±84.4)Pa, (928.3±56.3)Pa and (2582.4±282.2)Pa at strain rates of 2s-1, 20s-1 and 100s-1, respectively. Fung (0.833≤R2≤0.924), Gent (0.797≤R2≤0.875), Ogden (0.859≤R2≤0.944) and exponential (0.930≤R2≤0.972) models provided excellent fitting to experimental data up to 30% strain. Conclusions The infant cerebellum tissue shows a stiffer response with increase of the loading speed, indicating a strong strain-rate sensitivity. This study will enrich the knowledge on the material properties of infant brain tissue, which may augment the biofidelity of finite element model of human pediatric cerebellum.

Pedestrian Injury Patterns and Risk in Minibus Collisions in China

Background The minibus, with a nearly flat front, is widely used in China, especially in the underdeveloped regions, and results in large numbers of pedestrian injuries and deaths. The purpose of this study was to determine the injury patterns and risk for pedestrians involved in these crashes. Material/Methods We conducted an in-depth investigation of minibus/pedestrian accidents in Chongqing, China, occurring between September 2000 and April 2014. The enrolled pedestrians was classified into 3 groups: young (aged 14–44 years), middle-aged (aged 45–59 years), and elderly (aged over 60 years). Pedestrian injuries were coded according to the Abbreviated Injury Scale (AIS). Results A total of 109 pedestrians, with an average age of 55.7±16.2 years, were injured or killed – 30.3% were young, 23.9% were middle-aged, and 45.9% were elderly. Pedestrians hit by a minibus had a high proportion of head, chest, and extremity injuries – 84.4%, 50.5%, and 52.3%, respectively. In addition, impact speeds in excess of 75 km/h all ultimately resulted in fatalities. At an impact speed of 30 km/h, the risk of pedestrian fatality and AIS3+ injury are approximately 12.0% and 37.2%, respectively. At 50 km/h the risks are 65.2% and 96.9%, respectively, and at 70 km/h the risks are 96.3% and 99.9%, respectively. Conclusions A higher likelihood of chest injury was associated with being older and impact speed of over 40 km/h in minibus/pedestrian collision. Our data suggest that the injury patterns of pedestrians in minibus collisions differ from that in other vehicle/pedestrian collisions. These findings could contribute to better understanding of the injury patterns and risk of pedestrian in minibus collisions in China, which may play an important role in developing measures to improve traffic safety.

The Experimental and Case Study of Needle Marks on the Speedometer as the Physical Evidence for the Collision Speed Analysis

Abstract:  The collision speed is important in accident analysis, and needle marks can be helpful as the physical evidence. The deceleration impact system has been built to analyze the mechanics of the needle and the gauge plate. Two isolated groups were designed to record the speed values under the same sample labels from real crashes. The visualization platform was built for the first group to collect needle marks. The second group recorded the speed values by other methods. The collision deceleration, the gauge plate materials, and the collision directions determine the forming of the needle marks. There were eight positive results from the 23 effective samples (12 frontal, four side, and seven rear), with discernible tip and/or middle marks on gauge plates. Multiple marks have been distinguished effectively. The low‐ and high‐speed impacts have no obvious differences for real needle marks. It is more accurate for frontal impacts.

Analysis of 121 fatal passenger car-adult pedestrian accidents in China

To study the characteristics of fatal vehicle-pedestrian accidents in China，a team was established and passenger car-pedestrian crash cases occurring between 2006 and 2011 in Beijing and Chongqing, China were collected. A total of 121 fatal passenger car-adult pedestrian collisions were sampled and analyzed. The pedestrian injuries were scored according to Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS). The demographical distributions of fatal pedestrian accidents differed from other pedestrian accidents. Among the victims, no significant discrepancy in the distribution of ISS and AIS in head, thorax, abdomen, and extremities by pedestrian age was found, while pedestrian behaviors prior to the crashes may affect the ISS. The distributions of AIS in head, thorax, and abdomen among the fatalities did not show any association with impact speeds or vehicle types, whereas there was a strong relationship between the ISS and impact speeds. Whether pedestrians died in the accident field or not was not associated with the ISS or AIS. The present results may be useful for not only forensic experts but also vehicle safety researchers. More investigations regarding fatal pedestrian accidents need be conducted in great detail.

Mechanical Characterization of Immature Porcine Brainstem in Tension at Dynamic Strain Rates

Background Many brain injury cases involve pediatric road traffic accidents, and among these, brainstem injury causes disastrous outcomes. A thorough understanding of the tensile characterization of immature brainstem tissue is crucial in modeling traumatic brain injury sustained by children, but limited experimental data in tension is available for the immature brain tissue at dynamic strain rates. Material/Methods We harvested brainstem tissue from immature pigs (about 4 weeks old, and at a developmental stage similar to that of human toddlers) as a byproduct from a local slaughter house and very carefully prepared the samples. Tensile tests were performed on specimens at dynamic strain rates of 2/s, 20/s, and 100/s using a biological material instrument. The constitutive models, Fung, Ogden, Gent, and exponential function, for immature brainstem tissue material property were developed for the recorded experimental data using OriginPro® 8.0 software. The t test was performed for infinitesimal shear modules. Results The curves of stress-versus-stretch ratio were convex in shape, and inflection points were found in all the test groups at the strain of about 2.5%. The average Lagrange stress of the immature brainstem specimen at the 30% strain at the strain rates of 2, 20, and 100/s was 273±114, 515±107, and 1121±197 Pa, respectively. The adjusted R-Square (R2) of Fung, Ogden, Gent, and exponential model was 0.820≤R2≤0.933, 0.774≤R2≤0.940, 0.650≤R2≤0.922, and 0.852≤R2≤0.981, respectively. The infinitesimal shear modulus of the strain energy functions showed a significant association with the strain rate (p<0.01). Conclusions The immature brainstem is a rate-dependent material in dynamic tensile tests, and the tissue becomes stiffer with increased strain rate. The reported results may be useful in the study of brain injuries in children who sustain injuries in road traffic accidents. Further research in more detail should be performed in the future.

INVESTIGATION OF THE CAVITATION AND PRESSURE CHANGE OF BRAIN TISSUE BASED ON A TRANSPARENT HEAD MODEL IN ITS DECELERATING IMPACT

In this paper, a transparent physical head model with air bubbles to simulate the brain cavitation phenomena in head decelerating impact is presented. The transparent skull model was generated based on a real human skull through the turnover formwork technique, and a transparent gel was used to substitute the brain tissue. Air bubbles were created in the gel at the representative sites such as coup site and contrecoup site. After this, the head model was made to free fall from a position and impact on a fixed platform. The decelerating impacting process was recorded by a high-speed video camera and an accelerometer system. Through analyzing the video, the volume change of the air bubbles, namely, the mean pressure change of the air bubbles were calculated and compared. This new method has an advantage in investigating the brain cavitation phenomena using a direct and visual technique. The results showed explicitly and effectively that during the decelerating impact the contrecoup site air bubble was exposed mainly to a negative pressure which value became smaller and smaller in the first half of the impacting cycle and then came near to the normal level in the second half of the cycle; contrarily, the coup site air bubble was exposed mainly to a positive pressure which value became greater and greater in the first half of the impacting cycle and then came near to the normal level in the second half cycle. The probable biomechanics of the cavitation phenomenon is also given in this paper.

Developing an unmanned aerial vehicle-based rapid mapping system for traffic accident investigation

After a traffic accident, a diagram of the scene needs to be prepared as evidence in on-scene investigation. However, traditional methods to measure and map have their own defects. The aim of this study is the development of an unmanned aerial vehicle (UAV)-based mapping system to acquire scene diagrams rapidly. The camera calibration is explained in the study. This system provides approaches for lens distortion and perspective distortion elimination. A method for scene mapping from rectified images is also explained. The performance models for estimating the position error is developed and tested in different levels. The results show that the total root mean square error (RMSE) of the rectified image is 3.6 pixels, and the relative error of measurement in the rectified image can be controlled to –2.5%~2.5% when the UAV is at 11–112 m flight altitudes. This proposed method to draw scene diagrams is faster and easier than hand-drawing. It is indicated that the system provides a feasible method to obtain a scene diagram of a traffic accident.