alt Hacker News99% of bike fatalities involve car crashes. There is no styrofoam helmet which will protect against that, and the VaTech test notably does not model that type of crash.
To my knowledge, the only group that tried to test bike helmets against a car is Volvo -- and all helmets failed.
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https://www.facs.org/about-acs/statements/statement-on-bicyc...
Helmets reduce the risk of head injury by 48%, traumatic brain injury by 53%, facial injury by 23%, and fatal injury by 34%.2 Pediatric non-helmeted bikers have a 3-fold higher risk of serious head injury compared to helmeted bikers;3 one study suggests that helmet use may reduce the risk of head injury by 83%.4
Bicycle-related head injuries and deaths have decreased in states that have enacted bicycle helmet laws.5
Larger effects are found when legislation applies to all cyclists than when it applies to children only. 6
The key service performed by a cycling helmet is not turning a death situation into a permanently maimed situation (they do that, but that's a very rare occurrence), it's turning a life changing injury situation into a situation of some fractured bones that will be almost forgotten two months later. The life and death part is overrated.
I guess one reason people are so focused on that is because it's easy to quantify.