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Safer Roadways: A Complete Streets Guide
With the numerous environmental benefits, practitioners should work to implement these elements properly to provide for their successful growth and anticipated impact on the street. A range of issues from soil compaction, lack of space for roots to grow, physical damage or abuse, and litter can create a hostile environment for landscaping to flourish. Elements for inclusion in greenspaces should be carefully selected and incorporated early in the design process to allow for consideration of their needs, especially in situations where right-of-way is limited. Street Trees Trees and other plants help cool the environment, making vegetation a simple and effective way to reduce urban heat islands. The goal of adding street trees is to increase the canopy cover on the street and parking areas, and the percentage of the street’s surface either covered by or shaded by vegetation. The goal is not simply to increase the overall number of trees. The selection, placement, and management of all elements in the street should enhance the longevity of street trees and healthy, mature plantings should be retained and protected whenever possible. The heat island effect is a major concern in warm states as higher urban temperatures drive demand for air conditioning, leading to higher energy bills during the warmer months of the year. Heat islands can contribute to poor air quality, magnify the impacts of extreme heat events, and put people’s health at higher risk. Trees and vegetation lower surface and air temperatures by providing shade and through evapotranspiration. Shaded surfaces, for example, may be 20-45 o F cooler than the peak temperatures of unshaded surfaces. The use of trees and vegetation in urban and suburban contexts brings benefits beyond mitigating urban heat islands including: 25 Reduced energy use - Trees and vegetation that directly shade buildings decrease demand for air conditioning. Improved air quality and lower greenhouse gas emissions - By reducing energy demand, trees and vegetation decrease the production of associated air pollution and greenhouse gas emissions. They also remove air pollutants and store and sequester carbon dioxide. Enhanced stormwater management and water quality - Vegetation reduces runoff and improves water quality by absorbing and filtering rainwater. Reduced pavement maintenance - Tree shade and proper species selection can slow deterioration of street pavement, decreasing the amount of maintenance needed. Improved quality of life - Trees and vegetation provide aesthetic value, shade and comfort, habitat for many species, and can reduce noise. Additional related benefits of street trees include increased property values, neighborhood beautification, and enhanced human health and well‐being.
25 Environmental Protection Agency (EPA), Using Trees and Vegetation to Reduce Heat Islands https://www.epa.gov/heatislands/using-trees-and-vegetation-reduce-heat-islands
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