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原文传递 Why are Bike-Friendly Cities Safer for All Road Users?

题名：	Why are Bike-Friendly Cities Safer for All Road Users?
作者：	Marshall, W. E.; Ferenchak, N.; Janson, B.
关键词：	Bike-Friendly Cities, Fatalities, Bicyclists, Pedestrians safety, Land use
摘要：	Despite bicycling being considered on the order of ten times more dangerous than driving, the evidence continues to build that high-bicycling-mode-share cities are not only safer for bicyclists but for all road users. This paper looks to understand what makes these cities safer. Are the safety differences related to 鈥榮afety in numbers鈥?of bicyclists, or can they be better explained by differences in the physical places or the people that inhabit them? Based on thirteen years of data from twelve large U.S. cities, we investigated over 17,000 fatalities and more than 77,000 severe injuries across nearly 8,700 block groups via multilevel, longitudinal, negative binomial regression models. We hypothesize three potential pathways towards better road safety outcomes: i) travel behavior differences (e.g. 鈥榮afety in numbers鈥?or shifts to 鈥榮afer鈥?modes); ii) built environment differences (e.g. infrastructure that helps promote safer environments); and iii) socio-demographic and socio-economic differences (e.g. as some cities may be more populated by those with lower transportation injury risks). The results suggest that more bicyclists on the road is not the underlying reason these cities are safer for all road users. Better safety outcomes are instead associated with a greater prevalence of bike facilities 鈥?particularly protected and separated bike facilities 鈥?at the block group level, and even more strongly so, across the city as a whole. Higher intersection density, which typically corresponds to a more compact and lower-speed built environment, was strongly associated with better road safety outcomes for all road users. The variables representing gentrification also accounted for much of our explainable variation in safety outcomes. This first chapter helps support an evidence-based approach to building safer cities for all road users. While the policy implications of this work point to protected and separated bike infrastructure as part of the solution, we need to keep in mind that the potential pathways toward safer cites are complementary and should not be considered in isolation. Moreover, our results 鈥?particularly the safety disparities associated with gentrification 鈥?suggest equity issues and the need for future research. The extent of the data collected for this project allowed us to delve deeper into safety-related questions of equity, age, and infrastructure. Part 2 of this report looks at road safety like a health impact begs the question: who is the most impacted? Are there urban/rural differences? How equitable are the impacts along racial/ethnic lines or with respect to income? This research considers these questions through a spatial analysis of over 970,000 geocoded road fatalities in the U.S. that took place over the course of a 24-year period (1989鈥?012). Unlike other research, we also distinguished between crash location and the likely home zip code of those involved. Unfortunately, Americans are not bearing the public health impact of this problem equitably. We find road fatality disparities along racial and ethnic lines, particularly for pedestrians and bicyclists in predominantly black or Hispanic neighborhoods. Our results also point to significant discrepancies across the urban/rural and population density spectrums as well as by household income. For instance, lower income neighborhoods suffer from vehicle occupant fatality rates more than 3.5X higher than wealthier neighborhoods. Also, those living in our most rural zip codes endure vehicle occupant fatality rates approximately 6X higher than those living in our most urban zip codes. This suggests that transportation and land use planning that facilitates more access with less mobility can reduce unnecessary exposure and lead to road safety outcomes on par with the safest developed countries in the world.
报告类型：	科技报告