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)
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
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).