A Comprehensive Safety Assessment Methodology for Innovative Geometric Designs

As the population grows and travel demands increase, alternative interchange designs have become increasingly popular. The diverging diamond interchange is an alternative design that has been implemented in the United States. This design can accommodate higher and unbalanced flow and improve safety at the interchange. As the diverging diamond interchange is increasingly considered as a possible solution to problematic interchange locations, it is imperative to investigate the safety effects of this configuration. This report describes the selection of a comparison group of urban diamond interchanges, crash data collection, calibration of functions used to estimate the predicted crash rate in the before and after periods, and the Empirical Bayes before and after analysis technique used to determine the safety effectiveness of the diverging diamond interchanges in Utah. A discussion of pedestrian and cyclist safety is also included. The analysis results demonstrated statistically significant decreases in crashes at most of the locations studied. This analysis can be used by Utah Department of Transportation (UDOT) and other transportation agencies as they consider future implementation of the diverging diamond interchanges.

• Summary URL:
  https://www.ugpti.org/resources/reports/details.php?id=917
• Supplemental Notes:
  • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
• Corporate Authors:

  Utah State University, Logan

  Department of Civil and Environmental Engineering
  Logan, UT  United States 

  Mountain-Plains Consortium

  North Dakota State University
  Fargo, ND  United States  58108

  Office of the Assistant Secretary for Research and Technology

  University Transportation Centers Program
  Department of Transportation
  Washington, DC  United States  20590

  Utah Department of Transportation

  Salt Lake City, UT  United States 
• Authors:
  • Song, Ziqi
  • Lloyd, Holly
• Publication Date: 2018-7

Language

• English

Media Info

• Media Type: Digital/other
• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 94p

Subject/Index Terms

• TRT Terms: Bayes' theorem; Before and after studies; Calibration; Crash rates; Diamond interchanges; Evaluation and assessment; Geometric design; Highway safety; Methodology; Pedestrian safety; Urban areas
• Geographic Terms: Utah
• Subject Areas: Design; Highways; Operations and Traffic Management; Pedestrians and Bicyclists; Safety and Human Factors;

Filing Info

• Accession Number: 01680907
• Record Type: Publication
• Report/Paper Numbers: MPC 18-357
• Files: UTC, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Sep 20 2018 4:32PM