Landscaping of Highway Medians at Intersections

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 174 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.

• Record URL:
  https://fdotwww.blob.core.windows.net/sitefinity/docs/default-source/research/reports/fdot-bdk84-977-19-rpt.pdf
• 
• Summary URL:
  https://rosap.ntl.bts.gov/view/dot/26527
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/26526
• Corporate Authors:

  University of South Florida, Tampa

  Center for Urban Transportation Research
  4202 Fowler Avenue
  Tampa, FL  United States  33620-5373

  Florida Department of Transportation

  605 Suwannee Street
  Tallahassee, FL  United States  32399-0450
• Authors:
  • Lin, Pei-Sung
  • Fabregas, Aldo
  • Chen, Hongyun
  • Behzadi, Bijan
  • Wang, Qing
  • Lall, Sherrell
• Publication Date: 2013-9-30

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Maps; References; Tables;
• Pagination: 90p

Subject/Index Terms

• TRT Terms: Design standards; Highway factors in crashes; Intersections; Landscape design; Medians; State of the practice; Trees
• Geographic Terms: Florida
• Subject Areas: Design; Highways; Safety and Human Factors; I21: Planning of Transport Infrastructure; I82: Accidents and Transport Infrastructure;

Filing Info

• Accession Number: 01495163
• Record Type: Publication
• Contract Numbers: BDK84 977-19
• Files: TRIS, ATRI, STATEDOT
• Created Date: Oct 8 2013 10:31AM