Experimental and finite element analysis of rear impacts on bicycles with child seats

Introduction: In Japan, bicycles equipped with child seats have become popular in urban areas as a convenient means of transportation for preschool children. As such, it is necessary to conduct more studies and evaluations to prevent crashes and/or mitigate injuries of children in child-carrying bicycles. This study primarily aims to comprehend the kinematic behavior and injury risks to a child seated in a child seat attached to a bicycle when it is struck from the rear by a car. Method: First, collision tests were conducted to investigate the effects of bicycle tire sizes where a car collides against a bicycle with a rear-mounted child seat. The Hybrid III 3-year-old was seated in the child seat behind the Hybrid III 5F, representing a bicycle rider. Second, a finite element (FE) analysis was conducted for the same collision configurations as the tests. The FE analysis using Hybrid III dummy and THUMS models was employed, and the time frame was calculated from the moment the car began making contact with the bicycle to when the child collided with the adult. Results: The 26-inch tire bicycle lifted its front wheel upward, while the 20-inch tire bicycle pushed forward without lifting. The risk of injury to the child's head was in the order of ground impact, adult rider impact, and vehicle hood impact. The FE analysis confirmed that both the child passenger and an adult rider could sustain injuries when contacting with each other. Conclusions: Our current study has demonstrated that the kinematic behavior of the bicycle and potential injuries to the child passenger and adult rider differed between bicycles with 26 and 20-inch tire sizes. Practical Applications: The findings are useful in the selection of bicycles suitable for child seats and in the design of child seats tailored to bicycles with different tire sizes.