I have risked physical injury to avoid sensory overload. It's not that I'm unaware of the danger. It's a calculated risk I take, which I consider fully worthwhile.
It's an established fact that autistic facial expressions are often below the threshold of conscious awareness to non-autistic observers. I linked to research on this topic not long ago.
Next time you hear about an autistic kid having no sense of danger or no fear, consider the possibility that maybe the kid was suffering from sensory overload and those around them just couldn't see it on their face. Maybe that kid ran out into traffic or into the woods alone to get away from something that was making them miserable, and you just missed all the signs.