CMF / CRF Details

CMF ID: 4114

Install icy curve warning system

Description: Installation of icy curve warning system (ICWS)

Prior Condition:  Roadway without icy curve warning system

Category: Advanced technology and ITS

Study: Safety Effects of Icy Curve Warning Systems, Zhirui et al., 2012

Image: View the countermeasure image.

Star Quality Rating:3 Stars  [View score details]
Rating Points Total:85
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.08
Crash Reduction Factor (CRF)
Value:18  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:8
Crash Type:All
Crash Severity:All
Roadway Types:Not Specified
Street Type:
Minimum Number of Lanes:2
Maximum Number of Lanes:4
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:All
Minimum Speed Limit:40
Maximum Speed Limit:55
Speed Unit:mph
Speed Limit Comment:
Area Type:Rural
Traffic Volume:Minimum of 2850 to Maximum of 2950 Average Daily Traffic (ADT)
Average Traffic Volume:2900 Average Daily Traffic (ADT)
Time of Day:Not specified
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:1998 to 2009
Municipality:Lassen County
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (crashes):56 crashes before, 18 crashes after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Nov 01, 2012
Comments:It is not clear if the HSM SPFs were calibrated with California data. It is not clear if annual calibration factors were used to account for trends.