Weather, Traffic Accidents, and Exposure to Climate Change

Quantifying the costs of climate change requires measurement of direct effects as well as behavioral responses. While behavioral responses have been shown to increase costs, we identify responses that reduce costs, which we define as ‘voluntary exposure.’ We quantify the response of the transportation sector in terms of traffic accidents and travel demand to daily variation in weather. We find warmer temperatures and reduced snowfall are associated with a significant increase in fatal accidents. We find, however, that almost all of the estimated effect of temperature on fatalities is due to changes in exposure for pedestrians, bicyclists, and motorcyclists. While the application of these results to middle-of-the-road climate predictions suggests that weather patterns for the end of the century would lead to 397 additional fatalities per year, the associated welfare losses are almost completely offset by voluntary exposure benefits from increased travel by walking, biking, and motorcycling. To facilitate more accurate estimates of climate change impacts, we also introduce the empirical cumulative distribution function method to the economics literature for correcting baseline weather errors from climate simulations.