Quantifying the Characteristics of Real-World Bicycle Helmet Impacts

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Virginia Tech

Cycling is an increasingly popular mode of transportation and a preferred form of exercise worldwide. From 1990 to 2015, commuting via bicycle increased as much as four-fold in cities across North America and Europe. However, this increase in cycling is associated with an increase in cycling related fatalities and head injuries. The best way to prevent severe head injury while cycling is to wear a bike helmet. Bike helmets are designed to decrease the linear acceleration of the head, decreasing the rider's risk of severe head injuries, such as skull fracture. In order to sell a bike helmet, it must meet a minimum standard of protection based on linear acceleration of the head upon impact. However, bike helmet impacts are not completely linear in nature and experience a tangential component through angled impacts of the helmet, resulting in rotational accelerations and shear-strain at the skull-brain interface. This strain cause brain injuries such as concussion. Therefore, recent helmet advancements have aimed to decrease rotational acceleration of the head. To continue the advancement of helmet technology and the subsequent decrease of brain injury risk to riders, investigating the impact conditions of real-world impacts is pertinent. This thesis aimed to increase the current body of knowledge of cycling related head impacts. The first aim was to quantify real-world impact locations and analyze how impact location may influence helmet performance. The second aim of this thesis was to investigate the impact velocities and resulting kinematics of real-world crashes based on the magnitude of corresponding damage conditions. Additionally, this aim analyzed the impact conditions from cases which resulted in concussion. Together these studies aim to provide valuable real-world data to be used for the advancement of helmet technologies and design.

injury biomechanics, concussion, bike helmet, kinematics