An In-depth Investigation Of Minibus Collisions And Study On Injury Mechanicsm

The minibus, with a nearly flat front, is widely used in China, especially in the rural and underdeveloped regions, and results in large numbers of people injuries and deaths. Whatever, the traffic accidents with the minibus has increasing trend year by year. The people in minibus collisions usually were killed or seriously injured. The purpose of this study was to determine the injury mechanism and protection countermeasures for the people involved in minibus collisions by performing a special research of minibus collisions. Firstly, an in-depth investigation of minibus collisions from September 2000 to April 2014 in Chongqing, China was firstly conducted in this study, so as to clarify the characteristics and laws of minibus accident as well as the traffic injuries in minibus collisions. Secondly, two of the most common minibus in the accident database was chosen to build its finite element models according to the real vehicle dimension and materials. And the established models were validated for the further research. Thirdly, the findings in the previous investigation demonstrated that the minibus-pedestrian collisions have occupied the largest proportion of the minibus collisions in this investigation. Hence a study on the pedestrian injury mechanism and risk was conducted by using a combination of the established minibus models and THUMS human model. At last, two cases of minibus collisions were chosen to make the injury reconstruction, so as to determine the injury mechanism. We believe that this study could contribute to better understanding of injury mechanism in minibus collisions, which may play an important role in developi ng measures to improve traffic safety in minibus collisions.The main studying methods and results are as follows:(1) the in-depth investigation and analysis of the minibus collisionsIn order to acquire the accident data accurately, many new technologies were applied in the investigation. In general, a total of 333 cases were collected in this study. And almost 82.9% of the minibuses were the brand of Changan. And the minibus collisions with the pedestrian, van, fixed obstacles, passenger cars, buses and motorcycle accounted for 0.8%, 14.4%, 5.1%, 11.1%, 5.1% and 15.6%, respectively. Obviously, the minibus-pedestrian collisions were the most common type. In addition, the brain and chest were more easily injured in the minibus collisions. However, in the minibus to non-pedestrian collisions the poor compatibility of minibus is the main reason for the serious injury outcomes.(2) the establishment of the minibus FE modelsFinite element is one of the most important methods for the studies on traffic injury due to its outstanding advantage of predicting the local stress and strain. However the finite element models need to be built firstly. In this study, two minibuses FE models were built in this section based on its real overall dimensions and material properties. Then the established FE models were validated based on the comparison of the deformation modes, resultant acceleration of pillar B and the energy transaction between the simulations and tests. Finally, the established models were proved to be well acceptable, and these two models could be used for the further study.(3) pedestrian injury mechanism and risk in minibus collisionsThe minibus-pedestrian collisions were the main type of the minibus collisions. In this section, a study on pedestrian kinematic behavior and injury biomechanics in the minibus collisions under different impact speed(20 to 50 km/h) and different impact angle(0 °, 45 °, 90 °, 135 ° and 180 °) was performed. The conclusions could be draw that the injury risk of head, chest and lower extremities increased with the increasing of the impact speed. And there was no significant difference on the pedestrian’s kinematic behavior response in the same minibus collisions at the same impact velocity under different impact angles. However different collision speed and different vehicle front structure will result in different kinematic behavior. The risk of the base skull fracture was higher. The pedestrian injury risk was higher with being impacted at the angle of 90°, so the pedestrians should avoid crossing roads, or try the best to avoid being direct impact in side by minibus.(4) study on the typical minibus collisionTwo typical cases of minibus collisions was analyzed, one is to reconstruct the brain injuries for the children pedestrian based on the new THUMS head model, which was updated according to the results of experiments on the material properties of infant brain tissue. In this case, the child aged 4.5 years was hit to be dead on the spot while crossing the road. The main injury and cause for death were the brain injuries. In order to better represent this child pedestrian head, an updated THUMS model was derived from the original one based on the material testing results of the infant swine brain tissues as well as his real height and weight. Then the updated head model was used to reconstruct the brain injuries. And the simulated results could best match well with the head injury outcomes. In another case, an adult pedestrian was hit by the minibus while crossing the roads. However the overall impact process has been recorded by the surveillance system on the spot. The pedestrian kinematic behavior and impact parameters could be clearly analyzed from the surveillance video. In the meantime, the pedestrian was performed PMCT scanning to obtain the detailed injury information. Similarly, the simulated results could better predict the pedestrian injury outcomes.