CMF / CRF Details

CMF ID: 10438

Conversion of intersection into high-speed roundabout

Description: Conversion of intersection into high-speed roundabout

Prior Condition:  Minor Road Stop-Controlled Intersections

Category: Intersection geometry

Study: Evaluation of Roundabouts on High-Speed Roadways, Bagley, D.L., 2020

 
Star Quality Rating:3 Stars  [View score details]
Rating Points Total:105
Crash Modification Factor (CMF)
Value:0.62
Adjusted Standard Error:
Unadjusted Standard Error:0.17
Crash Reduction Factor (CRF)
Value:38  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:17
Applicability
Crash Type:All
Crash Severity:All
Roadway Types:All
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:
Minimum Speed Limit:35
Maximum Speed Limit:55
Speed Unit:mph
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:3-leg
Traffic Control:Roundabout
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:1999 to 2019
Municipality:
State:NC
Country:
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (sites):4 sites before, 4 sites after
Sample Size (site-years):12 site-years before, 12 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Jun 01, 2020
Comments: The number of crashes in the after period were not reported in this study, however, they have been recorded as 300 to give 10 points as a beneift of doubt for one or more of the following: (1) number of miles/sites in the reference/treatment group, (2) number of crashes in the references/treatment group, (3) reporting AADTs for the aggregate dataset but not for the disaggragate dataset used for CMF development.