Bicycling and the built environment: route choice and road safety

Abstract

Bicycling is an environment-friendly, healthy, and low-cost transportation mode that is especially suitable for short distance travels. There is a bicycling renaissance in the North America, and Seattle takes a leading role in this change. Increasing bicycle use in the US will amplify the exposure to crashes and injuries, and the outcomes will likely depend on the bicycle route choice and the risk factors in the built environment. Both bicyclists’ route preferences and bicycling safety performance are connected to the built environment features. To understand the effect of the built environment on bicycling, this dissertation addresses three interrelated research questions: (1) what built environment features are correlated with bicycle route choice, (2) how built environment features are correlated with bicycle crash frequency and bicycle crash risk, and (3) how built environment features are correlated with bicyclist injury severity. Using Seattle’s data, the research methodologies include advanced discrete choice models and count data models as key components. The results of this dissertation research show that changing the factors of land use, demographics, road network and design, contribute to a convenient, safe, and attractive bicycling environment, which encourages more bicycle use. The most significant built environment features impacting bicyclists’ route preferences and safety outcomes are: land use mixture, household density, employment density, bicycle facility types, waters and parks, commercial land use, street lights, street trees, slopes, and posted speed limit. Several policy implications can be drawn from the aforementioned results. First, in light of bicyclists’ route preferences, transportation planners should add cycle tracks and bike lanes on shortcuts in flat areas. In addition, local authorities should lower posted speed limits, improve street lighting conditions, and plant more street trees. Second, to reduce bicycle crash frequency and bicycle crash risk, local authorities should influence bicycling and driving behaviors with higher degrees of mixed land use, and place a greater percentage of commercial lands along popular bike routes. Transportation planners should encourage dense development and separate bike lanes from road traffic. Third, to mitigate bicyclist injury severity, local authorities should lower posted speed limits to reduce the risk of severe bicyclist injuries or separate bicycle lanes from road traffic. And transportation planners should, once again, advocate for the dense development and mixed land use, while improving street lighting and avoiding placing bike lanes on steep slopes in planning practice. Overall, encouraging compact development and implementing considerate roadway designs would promote safety and create a favorable bicycling environment.