Urban trees and traffic safety: Considering U.S. roadside policy and crash data

Abstract

In the mid to late 20th century, U.S. transportation agencies focused on traffic planning and design practices intended to achieve high levels of traffic capacity and safety for roads at lowest cost. Intangible values of the roadside such as community character and environmental systems were often overlooked, including the urban forest. Context Sensitive Solutions is a U.S. national policy intended to better incorporate local community values into transportation planning processes and products. The starting point for community-based roadside design is adequate research. This study analyzed national traffic collision data to address concerns about urban trees and traffic safety, including crash incidence and severity. Distinctions of urban and rural conditions were explored using descriptive, comparative, and predictive analysis methods. The findings acknowledge the serious consequences of tree crashes but distinguish urban/rural situations. Circumstances of tree crashes in urban settings are not well understood. Conclusions address future applications of flexible transportation design. The clear zone philosophy has been widely applied in rural settings but may need modification to better incorporate community values in urban design. Future research needs include testing of trees as a mitigation technology in safe roadside design and risk assessment as a community expression of value. © 2006 International Society of Arboriculture.