Study Details
Study Title: Development of a Crash Modification Factor for Conversion of a Conventional Signalized Intersection to a CFI
Authors: Cunningham et al.
Publication Date:AUG, 2022
Abstract: North Carolina is considered a progressive state in terms of alternative intersection implementation. Theservice life of many roadways has been extended because the profession is willing to push the envelope oftraditional intersection and interchange designs to consider alternatives – alternatives that in many casesextend the service life without the need for costlier designs. This research follows prior research in theunconventional intersection/interchange domain, which has helped bolster the use of promisingalternatives that look at possible safety and operational benefits. Specifically, this project helps build onthe current knowledgebase of continuous flow intersections (CFIs) by answering “Are these intersections asafe unconventional design form compared to other design alternatives?”
An Empirical Bayes study was conducted on 16 typical CFIs. Overall, CFIs were found to significantly reduce total crashes by 12.2%. The most significant feature impacting safety at CFIs was the use of parallel vs. standard right turns, with parallel right turns having significant safety benefits (29.6% reduction) across the board and standard right turns increasing crashes (15.6% increase) in nearly all categories. Looking only at sites with parallel right turns, skewed intersections showed significant reductions (29.4% and 30.1% reductions for both no-skew and skew, respectively); however, the findings for the no-skew condition for crash severity and type were better overall. Area type was not found to increase crashes; however, rural locations were significantly safer overall compared to urban/suburban designs (40.3% vs. 26.0% reduction). Although both site types were safe, 4-legged sites provide the best overall results for all crash category types and 3-legged sites were only significant in one of the categories. Last, although the number of crossover lanes did not increase crashes in either category, 2-lane crossovers were the only one that was found to significantly decrease crashes (34.9% reduction).
Study Citation: Cunnungham, C. T. Lee, T. Saleem, and R. Srinivasan. "Development of a Crash Modification Factor for Conversion of a Conventional Signalized Intersection to a CFI." Report No. FHWA/NC/2020-29. North Carolina Department of Transportation. Raleigh, North Carolina. (2022).
Study Report: Download the Study Report Document
CMFs Associated With This Study
Category: Intersection geometry
Countermeasure: Convert a conventional signalized intersection to a continuous flow intersection (CFI)
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.797 | 20.3 |  | All | K,A,B,C | All | All |
