I recently had a horrific accident where I went entirely over the handlebars, landing directly on my head and the left side of my body.
The impact was severe enough that I broke my collarbone in two places and fractured a couple of ribs. However, despite my head bouncing off the pavement twice, I walked away with absolutely zero head or neck injuries. No concussion, no trauma, nothing. The helmet took the entire force of the blow so my brain didn't have to. Looking at the damage to the helmet, it’s clear that it did exactly what it was engineered to do.