Study Details
Study Title: Safety Evaluation of Diverging Diamond Interchanges Design for Intersections in Minnesota
Authors: Walls et al.
Publication Date:JAN, 2018
Abstract: The installation of Diverging Diamond Interchanges (DDIs) has grown exponentially in the United States. There are limited real-world assessments of the safety benefits because the implementation of DDIs in the United States is relatively new. This study provides a project level safety effectiveness evaluation of two DDIs in Minnesota using two observational before-after evaluations. Before the implementation of the DDIs, both sites were classified as signalized intersections. The Naïve and Empirical Bayes (EB) before-after approaches were used to determine the safety savings of converting the signalized intersections into DDIs. Crash Modification Factors (CMF) were used to measure the safety effectiveness of the DDIs. Crash data and annual volume data from both sites before and after the DDI implementation was used in the analysis. The results indicate that the average CMF is 0.48 for the Naïve method and 0.42 for the EB method. The findings prove that the DDI design is a valid and reliable safety countermeasure.
Study Citation: Walls, J., M. B. Rab, Y. Qi., and R. N. Fries. "Safety Evaluation of Diverging Diamond Interchanges Design for Intersections in Minnesota". Presented at the 97th Annual Meeting of the Transportation Research Board, Paper No. 18-06071, Washington, D.C., (2018)
CMFs Associated With This Study
Category: Interchange design
Countermeasure: Convert at-grade intersections to Diverging Diamond Interchanges
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.42 | 58 |  | All | All | All |
