Study Details

Study Title: Developing Crash Modification Factors for Mini-Roundabouts

Authors: Avelar et al.

Publication Date:APR, 2023

Abstract: This study evaluated the safety effectiveness of mini-roundabout (MR) installations at two-way stop-controlled (TWSC) and all-way stop-controlled (AWSC) locations. Based on a longitudinal design including comparison sites, the database included three States: Washington, Michigan, and Maryland. Safety data were compiled for locations of known MR installations where the date of installation and prior intersection condition were known. Suitable comparison locations were included. The study included 15 MR locations from Washington, 6 from Michigan, and 6 from Maryland. Crash data from 2003 through 2019 were available from Washington, data from 2013 through 2019 from Michigan, and data from 2015 through 2019 from Maryland. A fully Bayesian evaluation based on the Washington crash data estimated crash reductions for MR converted from TWSC ranging from 31 to 42 percent for various crash types, which were statistically significant. The study found a statistically significant reduction of 39 percent in multivehicle crashes at MR converted from AWSC intersections from an additional analysis based on the complete database from all three States. This study also produced benefit–cost ratios of 2.88 and 2.87 for MR conversions from TWSC and AWSC, respectively, when only safety benefits were considered, whereas the ratio was 13.41 for AWSC intersections when operational benefits were also considered. These results indicate economic feasibility of MR installations.

Study Citation: Avelar, R., E.S. Park, and B. Kutela. "Developing Crash Modification Factors for Mini-Roundabouts." Report No. FHWA-HRT-23-019. Federal Highway Administration. McVean, VA (2023).

Related Citations: Avelar, R., E.S. Park, and B. Kutela. "Tech Brief - Developing Crash Modification Factors for Mini-Roundabouts." Report No. FHWA-HRT-22-109. Federal Highway Administration. McVean, VA (2023).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Intersection geometry

Countermeasure: Conversion of stop-controlled intersection to mini roundabout

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.63336.74 StarsAllAllNot specifiedUrban and suburban
0.577342.273 StarsAllK,A,B,CNot specifiedUrban and suburban
0.597740.234 StarsAllONot specifiedUrban and suburban
0.680231.983 StarsMultiple vehicleAllNot specifiedUrban and suburban
0.59840.23 StarsMultiple vehicleK,A,B,CNot specifiedUrban and suburban
0.638936.114 StarsMultiple vehicleONot specifiedUrban and suburban
1.1015-10.153 StarsAllAllNot specifiedUrban and suburban
0.685531.453 StarsAllK,A,B,CNot specifiedUrban and suburban
1.3-303 StarsAllONot specifiedUrban and suburban
1.1552-15.523 StarsMultiple vehicleAllNot specifiedUrban and suburban
0.783321.673 StarsMultiple vehicleK,A,B,CNot specifiedUrban and suburban
1.2676-26.763 StarsMultiple vehicleONot specifiedUrban and suburban

Countermeasure: Convert all-way, stop-controlled intersection to mini roundabout

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.881311.873 StarsAllAllNot specifiedUrban and suburban
0.574642.543 StarsAllK,A,B,CNot specifiedUrban and suburban
0.839316.073 StarsAllONot specifiedUrban and suburban
0.60839.23 StarsMultiple vehicleAllNot specifiedUrban and suburban
0.542245.783 StarsMultiple vehicleK,A,B,CNot specifiedUrban and suburban
0.77122.93 StarsMultiple vehicleONot specifiedUrban and suburban