On safety design of vehicle for protection of vulnerable road users: A review

Fatal and serious injuries of vulnerable road users (VRU) occur frequently in the events of vehicle impact. Front-end crashworthiness of vehicle can considerably affect VRU injuries in impact accidents, and vehicular design signifies a key issue in automobile engineering. This paper provides a comprehensive review on the state-of-the-art on the assessments and design of frontal structures for VRU protection through experiment, simulation and optimization methods. First, the impact-induced injury mechanisms of different human parts are evaluated. Second, different safety regulations and assessment procedures for VRU protection in the world are compared in detail, which include impact conditions, impact areas, injury indices, etc. Experimental testing platforms are outlined thoroughly for different types of VRU impacts. Third, virtual test systems for VRU protection are introduced by including multi-body system model, finite element analysis (FEA) model, and hybrid/coupling model. Fourth, a range of front-end structure designs are discussed comprehensively for reducing VRU injuries as reported in the literature. The contributions of front-end geometry and energy-absorption space on the impact responses of the head and lower extremity/pelvis of VRU are assessed. The passive and active protection designs of frontal structures, such as engine hood and bumper, are appraised in detail. A range of design optimization techniques are reviewed to highlight their effectiveness for reducing the injury of VRU. In addition, other protective measures for VRU are briefly introduced, such as helmet, wearable airbag, automatic emergency braking (AEB) system, automatic emergency steering (AES) system and Vehicle-to-Everything (V2X). Finally, concluding remarks and outlooks are provided for the future research and development on VRU protection.