Taken from the Pedestrian and Bicyclist Safety and Accommodation Course materials, NHI Course No. 38061
Every year in the United States about 500,000 people are injured riding bicycles. In these crashes, almost 900 people die in an average year. Of these deaths, almost 85% result from irreversible brain injury.
Of people seriously injured in bicycle crashes, nearly 75% sustain severe and/or permanent head injuries. Research from the Bicycle Helmet Safety Institute shows bicycle helmets to be about 88% effective preventing brain injuries.
One death every twelve hours and one head injury every four minutes could be prevented if all bicyclists in the United States wore helmets. Wearing a helmet is a good way to improve the odds in your favor. A fall from a bicycle or a crash into an object involves up to four separate collisions that can injure the brain.
1. In the first collision, the head strikes an object or vehicle.
2. In the second collision, the brain crashes violently forward against the liquid filled skull and then splashes backwards, colliding with it again. Each time the brain makes a violent impact it tears blood vessels and nerves and bruises the brain itself.
3. The third collision, a secondary crash, occurs when the head again hits an object, usually the pavement.
4. In the fourth collision, the brain again collides violently inside the skull, creating further damage to soft tissue and vessels of the brain. As the brain bleeds inside the skull, pressure builds. This slowly and steadily squeezes the brain, causing irreparable damage. Unless the pressure is relieved (usually by surgery) death eventually results.
The helmet absorbs large amounts of energy, reducing it to one-seventh or even one-tenth of its original force. The helmet also spreads the force over a larger area, reducing it even further.
The effect of each collision is significantly decreased when a properly fitted helmet is worn. By the time of the second collision a helmet that is too large, too loose or not securely fastened will be useless, because the initial impact will have knocked it off or askew.
A person sitting on a bike saddle and simply falling over onto the hard pavement or curb, can generate more than 2,000 G’s of force—more than twice the force necessary for a fatal head injury! Helmets reduce the “G” forces to the brain by a factor of up to 7!
Please wear your helmet!
Force: 60-65g's Results: An egg will crack or break.
Force: 100-150g's Results: Light to no injury; possible headache
Force: 150-250g's Results: Light concussion, amnesia
Force: 250-350g's Results: Serious concussion, unconsciousness, traumatic amnesia
Force: 400g's Results: Brain hemorrage, fracture possible, permanent injury likely
Force: 700g's Results: Survival not possible!
With apologies to Burma Shave: I think that I shall never see, a human head as hard as a tree. So wear your helmet when you ride... It will keep your brains inside.