Bicycle helmets are mandatory for children, and recent experiments show they do protect their heads from injury.

Researchers dropped water-filled helmeted skulls onto a metal anvil, testing whether the helmets prevented a fracture inducing impact.

They tested four different makes of helmets, as well as unhelmeted skulls.

While the method may sound crude, the results were conclusive.

The helmets offered their intended head injury impact protection in falls from as high as 3 feet off the ground.

Unhelmeted skulls experience impacts 4 to 8 times that of helmeted skulls.

Nonetheless, even the best helmet won't help unless it fits snuggly and is worn low over the forehead.