Answer: 45%
Explanation: According to Bicycle Helmet safety institute nearly 47% of the bicycle injuries are brain injuries are leading cause of hospitalisation of all the cases that take place on the streets.
Almost 2/3 of fatal crashes (74%) involved a head injury. Almost all the cases (97%) were not wearing a helmet. Helmet use among those bicyclists with serious injuries was low (13%), but it was even lower among bicyclists killed (3%).