Trees and Roadside Safety in U.S. Urban Settings

"Historically, transportation planning has focused on design objectives that achieve the highest levels of safety and capacity for roads at the lowest cost. This has frequently resulted in a roadside environment that ignores inherent characteristics such as community values and environmental amenities. The recent movement to incorporate context sensitive solutions into roadway and roadside designs has led to improved functionality of roads while maintaining high levels of safety. This study analyzes national traffic accident data to address questions relating to roadside attributes that are associated with accident incidence and severity, urban and rural spatial differences in accidents, the association between trees and roadside accident severity, and the implications for roadside planning, design, and management. The analysis involved the application of descriptive, comparative, and predictive modeling statistical methods to answer the research questions. The findings show that collisions with trees are more harmful than other types of accidents, accidents in rural areas are more harmful than accidents in urban areas, collisions with fixed objects are more frequent in rural areas than in urban areas, and that the statistical models predict accident outcomes with reasonable accuracy. From these findings, several conclusions may be drawn relating to context sensitive solutions. The clear zone philosophy, while arguably effective at improving safety, fails to incorporate community values and environmental amenities into design. A more comprehensive solution is proposed, including the implementation of collaborative design processes and the exploration of the idea of trees as technology to be incorporated into safe roadside designs." [Abstract]

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