Two important things about helmets:<p>1. Helmets are very very useful if you&#x27;re riding fast. In fact they are mandatory in all cycling sports. However most people don&#x27;t commute to work going much faster than they would if running, hence they are not very useful for them.<p>2. In countries where helmets are compulsory, the chilling effect of risking a fine for not wearing a helmet has meant a decrease in the number of cyclists. Now, since bike accidents are relatively rare, but the health effects of cycling to work rather than driving benefit every single cyclist, helmet laws tend to have a negative effect on public health.<p>This said, whenever I&#x27;m going for a sporty ride (longer, or faster than usual) I usually wear a helmet. When riding 5 minutes to meet a friend for a beer I don&#x27;t.