Influence of tree planting guidelines on street tree distribution along bus corridors

Abstract

As cities invest in public transportation to promote sustainable urban development, urban forestry presents an important yet underutilized opportunity to enhance commuter experience and environmental resilience, as street trees can significantly reduce urban heat island effects and enhance the comfort of bus users. This study examines how municipal tree planting regulations influence street tree density along bus routes in 15 U.S. cities. Analysis of street tree distributions revealed that in 73% of the cities, tree density was lower along bus routes compared to non-bus routes. Spacing regulations generally addressed minimum distances between trees; required setbacks from utilities; proximity to traffic control devices; distance from structures such driveways; and spacing from street corners. Using a generalized linear model and regulation severity scores, we assessed the impact of these regulations on tree density. The analysis revealed that certain requirements—such as minimum distances between trees, structures, traffic controls, and corners—were significantly associated with variations in tree density (p < 0.0001), however the degree of influence of the regulation on street tree density was dependent on whether the street had a bus corridor. These findings underscore the uneven influence of municipal regulations on street tree coverage and highlight the need for cities to evaluate how regulatory frameworks can support more equitable, climate-resilient transportation corridors.