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Like pedestrians, bicyclists are vulnerable road users, representing a population with a high risk of fatal and severe injuries in traffic accidents as they are unprotected during vehicle collisions. The objective of this study is to investigate the kinematics response of bicyclists and the correlation of the injury severity with vehicle impact speed. Twenty-four car-bicyclist cases with detailed information were selected for accident reconstruction using mathematical models, which was implemented in the MADYMO program. The dynamic response of bicyclists in the typical impact configuration and the correlation of head impact conditions were analyzed and discussed with respect to the head impact speed, time of head impact and impact angle of bicyclists to vehicle impact speed. Furthermore, the injury distribution of bicyclists and the risk of head injuries and fractures of lower limbs were investigated in terms of vehicle impact speed. The results indicate that wrap-around distance (WAD), head impact speed, time of head impact, head impact angle, and throw-out distance (TOD) of the bicyclists have a strong relationship with vehicle impact speed. The vehicle impact speed corresponding to a 50% probability of head AIS 2+ injuries, head AIS 3+ injuries, and lower limb fracture risk for bicyclists is 53.8 km/h, 58.9 km/h, and 41.2 km/h, respectively. A higher vehicle impact speed produces a higher injury risk to bicyclist. The results could provide background knowledge for the establishment or modification of pedestrian regulations considering bicyclist protection as well as being helpful for developing safety measures and protection devices for bicyclists. [ABSTRACT FROM AUTHOR]

• 69 in-depth vehicle-PTW accidents captured on video are analyzed. • A 5-steps human function failure model is used to excavate the accident causation. • Poor visibility exists widely in crossing and oncoming accident bundles. • A wider sensing area (field of view = 90°, view detection range = 35 m) is necessary to detect more effectively the conflict PTWs. As the use of powered two-wheeler (PTW) becomes increasingly prevalent, PTW accidents are emerging as a major threat to the people's life and property in China. Understanding the risky behaviors, psychological failures and kinematics in vehicle-to-PTW accidents is an important first step in addressing this issue. Here 69 vehicle-to-PTW accidents captured on video from the Traffic Accident Investigation and Research in China (TAIRC) database are selected and reconstructed. All accidents are categorized into different crash scenarios using a harmonized method. Accident causations are identified from the perspectives of praxeology and psychology. Kinematics characteristics, such as impact speed and relative position, are also analyzed. The results show the crossing accident bundle is the most frequent followed by rear, oncoming and run-up accident bundles, with proportions of 43.48 %, 27.54 %, 11.59 % and 17.39 % respectively. Accident causations of different crash scenarios have great differences whether in accident responsibilities or in psychological failures. For instance, the PTW riders who violate the traffic regulations need to be mainly responsible for most crossing accidents, whereas most rear accidents are blamed on drivers who fail to properly check their mirrors when they turn, turn around or change lanes. From the perspective of psychology, the perception failures encountered by both drivers and riders are a typical causation in crossing accidents, while it is a contributing factor in rear accidents that a failure of prognosis from the rider combined with a failure of perception from the driver. Visual obstruction exists widely in crossing and oncoming accident bundles. The impact speeds of vehicles and PTWs are often less than 40 km/h in all accident bundles. A wider sensing area (field of view = 90°, view detection range = 35 m) should be achieved to more effectively detect the conflict PTWs. These findings about vehicle-PTW accidents provide a stronger support for the development of prevention countermeasures and advanced driver assistance system. [ABSTRACT FROM AUTHOR]