Another safety device besides helmet and as critical or more critical is safety glasses, small pebbles kicked by your front tires or a small bug getting into your eye would cause instant sudden short duration transient blindness while riding, it won't be a good situation, if this scenario does not cause more permanent damage to rider's eyes, I may not necessarily wear a helmet every time I am riding or on my commute but I always have quality sunglasses during the day or clear safety glasses in early morning ride to work when it is still dark ourside?