title: Landscaping of highway medians and roadway safety at unsignalized intersections.
abstract: Well-planted and maintained landscaping can help reduce driving stress, provide better visual quality, and decrease over speeding, thus improving roadway safety. Florida Department of Transportation (FDOT) Standard Index (SI-546) is one of the more demanding standards in the U.S. for landscaping design criteria at highway medians near intersections. The purposes of this study were to (1) empirically evaluate the safety results of SI-546 at unsignalized intersections and (2) quantify the impacts of geometrics, traffic, and landscaping design features on total crashes and injury plus fatal crashes. The studied unsignalized intersections were divided into (1) those without median trees near intersections, (2) those with median trees near intersections that were compliant with SI-546, and (3) those with median trees near intersections that were non-compliant with SI-546. A total of 72 intersections were selected, for which five-year crash data from 2006-2010 were collected. The sites that were compliant with SI-546 showed the best safety performance in terms of the lowest crash counts and crash rates. Four crash predictive models-two for total crashes and two for injury crashes-were developed. The results indicated that improperly planted and maintained median trees near highway intersections can increase the total number of crashes and injury plus fatal crashes at a 90% confidence level; no significant difference could be found in crash rates between sites that were compliant with SI-546 and sites without trees. All other conditions remaining the same, an intersection with trees that was not compliant with SI-546 had 63% more crashes and almost doubled injury plus fatal crashes than those at intersections without trees. The study indicates that appropriate landscaping in highway medians near intersections can be an engineering technology that not only improves roadway environmental quality but also maintains intersection safety.
authors.affiliation: Embry-Riddle Aeronautical University, 600 S. Clyde Morris Blvd., Daytona Beach, FL 32124, United States. Electronic address: Hongyun.chen@erau.edu.
authors.forename: Hongyun
authors.initials: H
authors.lastname: Chen
authors.affiliation: Florida Institute of Technology, Melbourne, FL 32901, United States. Electronic address: afabregas@fit.edu.
authors.forename: Aldo
authors.initials: A
authors.lastname: Fabregas
authors.affiliation: Center for Urban Transportation Research, University of South Florida, 4202 East Fowler Avenue, CUT100, Tampa, FL 33620-5375, United States. Electronic address: lin@cutr.usf.edu.
authors.forename: Pei-Sung
authors.initials: PS
authors.lastname: Lin
mesh_terms: D000063:Accidents, Traffic / Q000401:mortality / Q000517:prevention & control / Q000706:statistics & numerical data*; D001334:Automobile Driving / Q000523:psychology; D004779:Environment Design; D005431:Florida; D006801:Humans; D008962:Models, Theoretical; D012449:Safety
keywords: Crash predictive models; Intersection safety; Landscaping of highway medians; Tree spacing and offset