Group 1 - The importance of wearing helmets while riding bicycles, motorcycles, and electric bikes is emphasized, as these vehicles provide little protection in accidents compared to cars [1][2][4] - Statistics indicate that one-third of non-fatal cycling accidents involve head injuries, highlighting the necessity of helmets [2] - The article discusses various types of helmets, including road bike helmets, mountain bike helmets, commuter helmets, and children's helmets, each designed for specific riding conditions [9][10] Group 2 - Safety certifications for helmets are crucial, with different standards applicable in various regions, such as GB 24429 in China, CE in Europe, and CPSC in North America [5][18] - Helmets have a limited lifespan, typically recommended to be replaced every three years due to wear and tear from environmental factors [8][29] - The article outlines the correct way to wear a helmet to ensure maximum protection, including proper fit and adjustment [11][13][14] Group 3 - Motorcycle helmets are categorized into full-face, A-type half helmets, and B-type half helmets, with full-face helmets providing the highest level of protection [19][23] - The article stresses that motorcycle accidents have a high fatality rate, with head injuries being the most common cause of death [16][17] - Electric bike helmets should meet motorcycle standards due to the potential for high speeds, especially when modified [31][32]