Bikes, helmets, and public health: decision-making when goods collide.

How ought public officials address policy choices that entail trade-offs between desirable public health goods? Increasing cycling improves public health both by promoting physical activity and by decreasing vehicle use, thus reducing vehicular emissions. Proponents of bicycle helmets argue that, used properly, they protect individual cyclists; however, there is concern that mandating helmet use may result in a decrease in cycling. In 2012, New York City Mayor Michael Bloomberg opposed a bicycle helmet mandate, concerned that it would have a negative impact on the city's cycling rate, which he had sought to increase. The mayor did not explain his rationale, leaving constituents unsure why he opposed the proposal. This case study underscores the challenge of creating public policy in the context of competing public health goods.