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MPC Research: A Comprehensive Safety Analysis of Diverging Diamond Interchanges

  • Jan 16, 2018 (10:00 - 11:00 am CT; 9:00 - 10:00 am MT)
    Webinar (desktop or laptop access)


REGISTRATION DEADLINE: Thursday, January 11, 2018


This webinar will present the research findings of the Mountain-Plains Consortium Research Project 480. This research was based on innovative geometric designs as a solution to the challenge of increased traffic volume with limited resources. This particular study focused on diverging diamond interchanges.

The diverging diamond interchange is a possible solution to problematic interchange locations because it can accommodate higher and unbalanced traffic flows. The analysis results demonstrated statistically significant decreases in crashes at most of the locations studied. This analysis can be used by government agencies and other transportation engineering professionals considering the implementation of diverging diamond interchanges. This presentation will discuss:

  • 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.
  • Empirical Bayes before and after analysis technique used to determine the safety effectiveness of the diverging diamond interchanges in Utah.
  • Discussion of pedestrian and cyclist safety is also included.


Holly Lloyd, a December 2016 graduate of Utah State University's master's program in civil engineering, was named the 2017 Student of the Year for USDOT's Region 8.

Holly grew up in Roy, Utah and attended Weber State University where she earned her bachelor degree in business administration with an emphasis in supply chain management. After working in the private sector, she decided to pursue a master degree in civil engineering emphasizing in transportation at Utah State University. Her masters project involved the analysis of the safety effectiveness of the diverging diamond interchanges in Utah, working with Dr. Ziqi Song as her advisor.

Target Audience

Traffic engineers, planners, roadway designers, and decision makers.

More Info

The above resource and more can be accessed by visiting the TLN Learning Management System (LMS).

NDSU Dept 2880P.O. Box 6050Fargo, ND 58108-6050