Yeah, that was part of my point, Emily, that how we behave is affected both by the real risk (traffic vs no traffic, slow vs fast) but also by the culture component. In a culture where "real cyclists " wear helmets, wearing one signals that you probably are aware of other things, like visibility. Or vice versa, not wearing one signals to me someone who doesn't care. I usually don't get to watch them long enough to tell if they're actually running real risks or not. I'm viewed by everyone I know as a dedicated cyclist, that is reason enough to not skip the helmet even if it's just for pedalling slowly uphill the half a mile on a cycle path from the grocery store.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett