CMF / CRF Details

CMF ID: 10086

Conversion of intersection to roundabout

Description: Conversion of stop- and signal-controlled intersections into roundabouts

Prior Condition:  Intersections without roundabouts

Category: Intersection geometry

Study: Safety Evaluation of Roundabouts in Georgia, Gbologah et al., 2019

 
Star Quality Rating:3 Stars  [View score details]
Rating Points Total:80
Crash Modification Factor (CMF)
Value:0.512
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value:48.8  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:
Applicability
Crash Type:All
Crash Severity:K (fatal),A (serious injury),B (minor injury),C (possible injury)
Roadway Types:Not specified
Street Type:
Minimum Number of Lanes:
Maximum Number of Lanes:
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:Undivided
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit:
Speed Limit Comment:
Area Type:All
Traffic Volume:
Average Traffic Volume:
Time of Day:All
If countermeasure is intersection-based
Intersection Type:Roadway/roadway (not interchange related)
Intersection Geometry:4-leg
Traffic Control:Not specified
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:2007 to 2014
Municipality:
State:GA
Country:
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (crashes):50 crashes before, 48 crashes after
Sample Size (sites):13 sites before, 13 sites after
Sample Size (site-years):54 site-years before, 63 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Jul 26, 2019
Comments:Applies to the conversion of a four-leg intersection to a single-lane roundabout. CMF analysis includes roundabout locations with less than four average observed crashes per year in before period as one sample, roundabout locations with just a single data-year of crashes in before or after period, and omits roundabout locations with zero observed crashes in the before period.