CMF / CRF Details

CMF ID: 8349

Install w-beam guardrail or concrete barrier


Prior Condition: No roadside barrier

Category: Roadside

Study: Evaluation of the Safety Effectiveness of Installing Roadside Barriers with Different Driver, Vehicle, Weather, and Time of Day Conditions, Park et. al., 2016

Star Quality Rating: 4 Stars   [View score details]
Crash Modification Factor (CMF)
Value: 0.73
Adjusted Standard Error:
Unadjusted Standard Error: 0.07
Crash Reduction Factor (CRF)
Value: 27   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error: 7
Crash Type: Run off road
Crash Severity: K (fatal),A (serious injury),B (minor injury)
Roadway Types: Principal Arterial Other Freeways and Expressways
Number of Lanes: 2 to 5
Road Division Type:
Speed Limit: 50-70 mph
Area Type: Not specified
Traffic Volume: Minimum of 35000 to Maximum of 104600 Annual Average Daily Traffic (AADT)
Average Traffic Volume:
Time of Day: All
If countermeasure is intersection-based
Intersection Type:
Intersection Geometry:
Traffic Control:
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used: 2003 to 2011
State: FL
Type of Methodology Used: Before/after using empirical Bayes or full Bayes
Sample Size (crashes): 237 crashes before, 160 crashes after
Sample Size (sites): 147 sites before, 147 sites after
Sample Size (miles): 68 miles before, 68 miles after
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Jan-17-2017
Comments: CMF is based on a Full Bayes analysis.