"In the city, I do not wear a helmet.  First off, I think it is up to the person riding if he/she wants to wear a helmet.  Its their life in their hands and if they want to ride without for whatever reason that may be, then let them have that choice.  Don't yell out "wear a helmet" or "where's your helmet?".  When I ride on the trails on my mtb, I always wear a helmet, when I ride my road bike, I always wear a helmet.  But for me, riding in the city is my transportation choice.  I ride everywhere I need to go.  For me, I choose not to ride a helmet when riding to and from work because its a lot lower risk.  I am on a bike path and going lower speed.  The bigger thing behind my reason is similar to the dutch way of thinking.  If everyone had to ride a helmet, there would be even less people riding bikes.  Its one more reason to keep someone off a bike is the danger factor.  By wearing a helmet, its putting this picture out to the public that this is an unsafe activity.  Meaning, you want to try this?  Because if you do, you WILL get hurt.  But that's just not true.  Yes, accidents happen, but they do with everything we do.  Driving, walking, running.  Biking should be portrayed as an "everyone can do it" mode of transportation.  This is just the case in Europe, where bikes are not all about sport, but for a mode to get from A to B in the fastest way across the city.  If more people didn't wear helmets, I think it would give the impression to more people that its something they could do as well!"