[bdcs]

Ugh, why no helmet? They reduce a multitude of bicycle head injuries by 2-3x [0]

[0] https://academic.oup.com/ije/article/46/1/278/2617198

[b3morales]

Roughly speaking they help non-collision injuries (wheel failure, thrown by a pothole, slipped on an icy turn), but don't do much if the cyclist is struck by a car.