4. URBAN TREE AND UTILITY POLE RECOMMENDED PRACTICES
Urban practitioners have the opportunity to influence the design of highway and street projects, and mitigate safety concerns before they arise.43 The following section describes a number of practices for enhancing safety while introducing trees and utility poles into the urban roadside environment.
4.1 Lateral Offset
Utility poles and trees of mature diameters greater than 4 inches are recommended to be located at least 6 feet behind the curb of urban roadways. Lateral offset always need to be greater than 4 feet behind the curb. See also the AASHTO Roadside Design Guide for additional guidance.
It is recommended that trees and utility poles be located so as not to restrict the drivers' sight. Some suggestions for improving sight distance and visibility include:
- Keeping intersection sight triangles clear of any visual obstructions between 3 feet and 10 feet vertically.
- Placing trees and poles outside of established sight distance parameters for horizontal curves on ramps.
- Locating trees and poles where their presence will not obstruct regulatory, warning, or advisory signing.
It is also advisable to place trees where their shadows will not interfere with the solar impact of snow and ice melting.
As plantings are considered, it is optimal to avoid tree species with the following characteristics:
- Their fruit, seed pods, brittle branches, or leaves would obstruct drainage facilities resulting in gutter spread into the travel lanes.
- Their fruit is edible and could attract humans or wildlife into the roadway, creating a safety hazard.
4.5 Worker Safety
Trees and shrubs need to be planted in locations where their maintenance will not place workers in close proximity to live traffic.
43 Federal Highway Administration, Urban Tree and Landscape Safety, Task T-06-005 (McLean, VA: February 2, 2009), p.96.