CMF / CRF Details

CMF ID: 4140

Change permissive left-turn phasing to protected only or protected/permissive

Description: Treatment group includes intersections where signal phases were changed from permissive to protected-only or protected/permissive.

Prior Condition:  Treatment group includes intersections where signal phases were changed from permissive to protected-only or protected/permissive.

Category: Intersection traffic control

Study: Left-turn Phase: Permissive, Protected, or Both?, Li Chen, Cynthia Chen, and Reid Ewing, 2012

 
Star Quality Rating:2 Stars  [View score details]
Rating Points Total:65
Crash Modification Factor (CMF)
Value:0.58
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value:42  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:
Applicability
Crash Type:All
Crash Severity:All
Roadway Types:Not Specified
Street Type:
Minimum Number of Lanes:1
Maximum Number of Lanes:5
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:Urban
Traffic Volume:
Average Traffic Volume:
Time of Day:All
If countermeasure is intersection-based
Intersection Type:Roadway/roadway (not interchange related)
Intersection Geometry:3-leg,4-leg,More than 4 legs
Traffic Control:Signalized
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:1995 to 2009
Municipality:New York City
State:NY
Country:USA
Type of Methodology Used:Simple before/after
Sample Size (crashes):2447 crashes before, 564 crashes after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Nov 01, 2012
Comments:The corresponding change in crashes in the comparison group was a 35 percent reduction in total crashes. This could be used to adjust the treatment effect to account for other factors not related to the treatment.