CMF / CRF Details

CMF ID: 4271

Change permissive left-turn phasing to protected/permissive

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

Prior Condition:  Permissive phasting

Category: Intersection traffic control

Study: Evaluation of Safety Strategies at Signalized Intersections, Srinivasan, et al., 2011

Star Quality Rating:5 Stars  [View score details]
Rating Points Total:140
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.036
Crash Reduction Factor (CRF)
Value:-7.5  (This value indicates an increase in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:3.6
Crash Type:Rear end
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:Urban
Traffic Volume:
Average Traffic Volume:
Time of Day:Not specified
If countermeasure is intersection-based
Intersection Type:Roadway/roadway (not interchange related)
Intersection Geometry:4-leg
Traffic Control:Signalized
Major Road Traffic Volume:Minimum of 4857 to Maximum of 74990 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 1466 to Maximum of 42723 Annual Average Daily Traffic (AADT)
Average Major Road Volume :31386 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :15904 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used:1997 to 2007
Country:Canada and USA
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (sites):71 sites after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Dec 06, 2012
Comments:Average major and minor road volumes are computed based on weighted average in NC and Toronto. AADT applies to all sites.Assumed 2 crashes per site in both the before and after periods to estimate sample size.