CMF / CRF Details

CMF ID: 10088

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]
Crash Modification Factor (CMF)
Value: 0.503
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value: 49.7   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:
Applicability
Crash Type: All
Crash Severity: All
Roadway Types: Not specified
Number of Lanes:
Road Division Type: Undivided
Speed Limit:
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: United States
Type of Methodology Used: Before/after using empirical Bayes or full Bayes
Sample Size (crashes): 463 crashes before, 337 crashes after
Sample Size (sites): 18 sites before, 18 sites after
Sample Size (site-years): 72 site-years before, 90 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 or multilane 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 roundabout locations with zero observed crashes in the before period.