CMF / CRF Details

CMF ID: 11146

Convert to roundabout interchanges

Description: Convert to interchange roundabouts with either a single roundabout or a pair.

Prior Condition: Signal-controlled ramp terminal on diamond interchange

Category: Interchange design

Study: Are Roundabouts Safe and Economically Viable Replacing Conventional Diamond Interchange Ramp Terminals?, Boris Claros, Beau Burdett, Madhav Chitturi, Andrea Bill, and David A. Noyce, 2021

Star Quality Rating: 3 Stars   [View score details]
Rating Points Total: 95
Crash Modification Factor (CMF)
Value: 0.594
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value: 40.6   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Type: All
Crash Severity: K (fatal),A (serious injury),B (minor injury),C (possible injury)
Roadway Types: Principal Arterial Other Freeways and Expressways
Street Type: Not Specified
Minimum Number of Lanes:
Maximum Number of Lanes:
Number of Lanes Direction: Not Specified
Number of Lanes Comment:
Crash Weather: Not specified
Road Division Type:
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit: mph
Speed Limit Comment: Posted speed limits for freeways were between 55 mph and 70 mph. Posted speed limits for crossroads were between 35 mph and 45 mph.
Area Type:
Traffic Volume:
Average Traffic Volume:
Time of Day: Not specified
If countermeasure is intersection-based
Intersection Type: Roadway/roadway (interchange ramp terminal)
Intersection Geometry: No values chosen.
Traffic Control: Roundabout
Major Road Traffic Volume: Minimum of 7493 to Maximum of 30700 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume: Minimum of 1900 to Maximum of 9400 Annual Average Daily Traffic (AADT)
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:
State: MO, WI
Country: USA
Type of Methodology Used:
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Aug-25-2022
Comments: AADT on exit ramps were between 1,900 and 9,400 vpd. AADT on entrance ramps were between 2,133 and 9,267 vpd. AADT on crossroad approaches were between 7,493 and 30,700 vpd.