ROADSIDE URBAN TREES Balancing Safety and Community Values

streets are not just thoroughfares for motor vehicles. They often double as public spaces where people walk, shop, meet, and generally participate in many social and recreational activities that make urban living enjoyable. Urban foresters, designers, and planners encourage streetscape tree planting to enhance the livability of urban streets. Yet conventional transportation safety guidelines regard trees and other fixed objects along a roadside as hazards and strongly discourage their use. A prevailing principle in roadside design is the " clear zone, " which is an expression of the idea of a forgiving roadside. Today's engineering practices encourage design of roadsides that allow a vehicle leaving any roadway to safely recover before encountering a potentially hazardous, fixed object. High-quality trees play many roles in community improvement. Physical features such as street trees and on-street parking may buffer pedestrians from hazardous oncoming traffic. Landscape provides spatial definition to the public right-of-way. Extensive research has documented environmental, social, and economic benefits for communities , municipalities, and regions. Directly related to transportation, studies have found that drivers judge forested urban highways to have higher visual quality. People have more favorable perceptions of communities with green roads, and visitors to forested central business districts claim they will spend 9 to 12 percent more for products. Drivers seeing natural roadside views show lower levels of stress and frustration compared to those viewing built settings. Unfortunately, this evidence is not yet widely acknowledged within the transportation industry. Tree crash statistics are often weighed against anecdotal reports of tree benefits in transportation decision making. Discussions of roadside trees are largely framed in terms of aesthetic values, which are not viewed as justification for tree retention or planting when weighed against long-held safety standards. Context Sensitive Solutions is a U.S. national policy intended to better incorporate local community values into transportation planning processes and products. Many communities seek to better integrate the needs of pedestrians and local developmental objectives into the design of their roadways. The starting point for better community-based roadside design is adequate research. Circumstances of tree crashes in urban settings are not now well understood. Few accident studies have looked closely at urban settings. Clear zones and other forgiving design practices have a less than clear relationship to safety in urban environments—and may actually reduce safety. There is a slowly growing body of evidence suggesting that the inclusion of trees and other streetscape features in the …