I think the biggest factor is knowing how to fall, and I'm glad they included it, although I wish it was at the top because in my experience it's so important, and potentially applies to any situation in life where accidents can happen, not just when you're padded up for action sports.

Of course, knowing how fall comes with a strong intuition about when you're going too fast to manage a fall without serious injury. How fast is too fast is particular to the individual and their experience.

Most people are going faster than they think. 20MPH slide is enough to occasionally put people in the hospital

a "sudden dismount" at 15 mph can annihilate your teeth, or cause severe TBI. Even tripping while walking in the wrong way and hitting your head can lead to death.

If you're going slow, you can maybe skimp on some of the abrasive protection, but you should still have something on your skull and joints.