Study Details

Study Title: Landscaping of Highway Medians at Intersections

Authors: Lin et al.

Publication Date:SEP, 2013

Abstract: Recent interest in road beautification initiatives as a way to help economic growth has led to a number of changes in landscaping policies in Florida. These changes raised the need to evaluate whether the criteria in the landscaping requirements in the Florida Department of Transportation's Design Standard Index 546 (SI -546) remain valid for providing guidance on the installation of trees on medians at intersections. This project evaluates the safety performance of SI-546 with respect to landscaping on medians at intersections through the following objectives: (1) review the current landscaping criteria; (2) develop a computational procedure to analyze landscaping configurations; and (3) perform an empirical study of the safety performances of SI-546. In the literature review, landscaping policies from 29 states were compiled and summarized, and SI-546 was found to be the leading, critical standard to set tree setbacks and detailed spacing requirements at highway medians near intersections. This study validated the current SI-546 and provided recommendations. In this study, a fully functional computational tool was developed. This tool allows landscape architects and design engineers to obtain a variety of visibility performance measures. For the assessment of median tree setback setting in SI -546, 300 median fixed-object crashes were analyzed. For the empirical analysis, the study intersections were divided into three groups: (1) those with median trees near the intersections, compliant with SI -546; (2) those without median trees near the intersections; and (3) those with median trees near the intersections noncompliant with SI-546. Seventy-two intersections were selected for data collection. From 1 74 crashes examined in this study, the sites compliant with SI-546 had the best safety performance, presenting the lowest crash counts for 4-way and T-intersections, crash rates, and injury severity levels among the three groups. Sites with trees noncompliant with SI-546 showed a higher crash rate at the different posted speed limits than those of the other groups.

Study Citation: Lin,P.,Fabregas,A.,Chen,H.,Behzadi,B.,Wang,Q.,and Lall,S., "Landscaping of Highway Medians at Intersections." Florida Department of Transportation, Tallahassee,FL,(2013)

Study Report: Download the Study Report Document

CMFs Associated With This Study

Category: Access management

Countermeasure: Landscape Medians at Intersections

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.68-682 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysNot specified
3.26-2262 StarsAllK,A,B,CPrincipal Arterial Other Freeways and ExpresswaysNot specified
0.82182 StarsAllK,A,B,CPrincipal Arterial Other Freeways and ExpresswaysNot specified