Development of Safety Performance Functions for Urban and Suburban Multilane Highways in Georgia

Details

• Creators:
  Yang, Jidong J. ; Liu, Jun ; Xu, Ningzhe ; Su, Yanfang ; Yang, Chenxuan ; Barnett, Timothy E. ; Jones, Steven ; Xue, Jialun
• Corporate Creators:
  University of Georgia Research Foundation, Inc. ; Board of Trustees of The University of Alabama
• Corporate Contributors:
  Georgia. Department of Transportation. Office of Performance-Based Management & Research ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Corridors Crash Modification Factors Highway Safety Median Lanes Multilane Highways Performance Evaluations Safety Performance Functions Urban Areas
• Publication/ Report Number:
  FHWA-GA-26-2504
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Georgia
• Edition:
  Final Report (November 2022 – June 2026)
• Corporate Publisher:
  Georgia. Department of Transportation. Office of Performance-Based Management & Research
• Abstract:
  This report presents the findings of the Georgia Department of Transportation (GDOT) Research Project 25-04 which concludes Research Project 22-27, which aimed to develop Georgia-specific safety performance functions (SPFs) and estimate crash modification factors (CMFs) to evaluate the safety effectiveness of different median treatments on urban and suburban multilane highways. Leveraging six years (2016–2021) of crash, roadway, and traffic data—with a focus on 2018–2021 data—the research developed segment-level and corridor-level SPFs and estimated CMFs to quantify the impacts of three median types on crash frequency and severity: undivided/no median, flush medians (two-way left-turn lanes [TWLTLs]), and raised medians. SPFs were developed separately by median type and crash severity (all crashes [KABCO] and fatal and injury crashes [KAB]), incorporating key variables such as traffic volume (annual average daily traffic [AADT]), truck percentage, access point density, intersection density (corridor-level), land use, and area type (urban versus suburban). Findings indicate that raised medians consistently provide the greatest safety benefits in high-volume and high-conflict settings (e.g., AADT > 25,000, dense intersections), and TWLTLs are effective under moderate traffic conditions (AADT 15,000–25,000) with low truck percentages. Undivided/no-median highways are generally suitable only in low-volume, low-conflict environments (AADT < 20,000). CMF-informed policy recommendations were developed to support GDOT in making context-sensitive, data-driven decisions about median design for urban and suburban multilane highways across Georgia, aligning with the department’s design guidelines.
• Format:
  PDF
• Funding:
  PI # 0019321
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:977ac6e86f06e6b873d9c0f3de6402247823cbe72cf40fdc4d1c406fd88703f796531686d15d107c61e2359fb8bbd656ed05f6b69f313545a92fb285ffa6a046
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/91917/dot_91917_DS1.pdf
• File Type:
  [PDF - 22.60 MB ]