Urban Trees and Roadside Safety

This paper describes a research project performed as part of a clear zone implementation program for Huntsville, Alabama. A literature review and a field investigation program were the two major components of the project. Investigators visited the sites of 164 urban tree accidents to identify their characteristics. Time of day, day of week, accident severity, roadway geometry, pavement surface condition, lateral distance from the pavement to the tree, tree size, and tree density were among the characteristics investigated. Among the major findings were that: there were strong similarities between urban and rural tree collision patterns, but urban accidents were less severe; the outside of horizontal curves was highly over‐represented; and 80% of the collisions were within 20 ft of the pavement edge. Recommendations were provided for city ordinances and operating procedures for future tree plantings. A plan was also devised for retrofitting the clear zone concept to existing trees along city streets.