CMF / CRF Details

CMF ID: 6889

Convert diamond interchange to Diverging Diamond Interchange (DDI) or Double Crossover Diamond (DCD)

Description: Convert a diamond interchange to a Diverging Diamond Interchange (DDI) or a Double Crossover Diamond (DCD)

Prior Condition: Conventional diamond interchange

Category: Interchange design

Study: Safety Evaluation of Diverging Diamond Interchanges in Missouri, Edara et al., 2015

Star Quality Rating: 4 Stars   [View score details]
Rating Points Total:
Crash Modification Factor (CMF)
Value: 0.374
Adjusted Standard Error:
Unadjusted Standard Error: 0.041
Crash Reduction Factor (CRF)
Value: 62.6   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error: 4.1
Crash Type: All
Crash Severity: K (fatal),A (serious injury),B (minor injury),C (possible injury)
Roadway Types: All
Street Type:
Minimum Number of Lanes: 3
Maximum Number of Lanes:
Number of Lanes Direction: Both Directions
Number of Lanes Comment: Multi Lane
Crash Weather: Not specified
Road Division Type:
Minimum Speed Limit: 60
Maximum Speed Limit: 65
Speed Unit: mph
Speed Limit Comment: 60 - 65 mph on Freeway / 35 - 40 mph on Crossroad
Area Type: Not specified
Traffic Volume:
Average Traffic Volume:
Time of Day: All
If countermeasure is intersection-based
Intersection Type: Other
Intersection Geometry:
Traffic Control: Other
Major Road Traffic Volume: Minimum of 32604 to Maximum of 151923 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume: Minimum of 16087 to Maximum of 29275 Annual Average Daily Traffic (AADT)
Average Major Road Volume : 72987 Annual Average Daily Traffic (AADT)
Average Minor Road Volume : 23948 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used: 2005 to 2013
State: MO
Country: USA
Type of Methodology Used: Before/after using empirical Bayes or full Bayes
Sample Size (crashes): 398 crashes before, 104 crashes after
Sample Size (sites): 6 sites before, 6 sites after
Sample Size (site-years): 21 site-years before, 14.83 site-years after
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Nov-01-2015
Comments: This CMF applies to the entire interchange footprint (i.e., ramp terminals, ramp segments, speed-change lanes, crossroad, and freeway segment).