One thing I find lacking in helmets is a better visor to keep the sun out of our eyes particularly during sunrise and sunset. That could go a long way to increasing safety while wearing a helmet. I had to improvise with a chunk of rubber from an inner tube, hot glued to the tip of my visor. It doesn't take much, only about 3/4" but it does a heck of a job. It's not pretty but it's practical, and could save me from crashing. Riding with one hand to shade my eyes isn't a good thing..
Wear sunglasses and or a cycling cap. I make it a point to wear sunglasses while riding all the time. Having a bug fly in your eye during a downhill is no fun, neither is being blinded by the sun.