CMF / CRF Details

CMF ID: 9669

Changing left turn phasing from protected-permissive to flashing yellow arrow (FYA)

Description: CMFs are calculated the intersection level and not the treated approach(es) level.

Prior Condition:  Protected-permissive operation with circular green indication for the permissive

Category: Intersection traffic control

Study: Safety Effects of Flashing Yellow Arrows Used in Protected Permitted Phasing: Comparison of Full Bayes And Empirical Bayes Results, Appiah et al., 2018

Image: View the countermeasure image.

Star Quality Rating:4 Stars  [View score details]
Rating Points Total:120
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.066
Crash Reduction Factor (CRF)
Value:30  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:6.6
Crash Type:Angle
Crash Severity:All
Roadway Types:Not specified
Street Type:
Minimum Number of Lanes:
Maximum Number of Lanes:
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit:
Speed Limit Comment:
Area Type:All
Traffic Volume:
Average Traffic Volume:
Time of Day:Not specified
If countermeasure is intersection-based
Intersection Type:Roadway/roadway (not interchange related)
Intersection Geometry:3-leg,4-leg
Traffic Control:Signalized
Major Road Traffic Volume:Minimum of 3678 to Maximum of 28605 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 561 to Maximum of 8625 Annual Average Daily Traffic (AADT)
Average Major Road Volume :12226 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :3383 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used:2008 to 2016
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (sites):28 sites before, 28 sites after
Sample Size (site-years):190 site-years before, 62 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Oct 27, 2018
Comments: The number of crashes in the after period were not reported in this study, however, they have been recorded as 300 to give 10 points as a beneift of doubt for one or more of the following: (1) number of miles/sites in the reference/treatment group, (2) number of crashes in the references/treatment group, (3) reporting AADTs for the aggregate dataset but not for the disaggragate dataset used for CMF development.