CMF / CRF Details

CMF ID: 6096

Improve left-turn lane offset to create positive offset

Description: Improve left-turn lane offset to make the left-turn lanes with positive offset

Prior Condition:  Left-turn lanes with negative offset

Category: Intersection geometry

Study: Safety Evaluation of Offset Improvements for Left-Turn Lanes, Persaud et al., 2009

Image: View the countermeasure image.

Star Quality Rating:3 Stars  [View score details]
Rating Points Total:80
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.09
Crash Reduction Factor (CRF)
Value:35.6  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:9
Crash Type:All
Crash Severity:K (fatal),A (serious injury),B (minor injury),C (possible injury)
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:Not specified
Traffic Volume:
Average Traffic Volume:
Time of Day:All
If countermeasure is intersection-based
Intersection Type:
Intersection Geometry:4-leg
Traffic Control:
Major Road Traffic Volume:Minimum of 7,150 to Maximum of 29,200 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 2,200 to Maximum of 13,350 Annual Average Daily Traffic (AADT)
Average Major Road Volume :18,892 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :6,668 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used:1983 to 2005
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (crashes):305 crashes before, 62 crashes after
Sample Size (sites):12 sites before, 12 sites after
Sample Size (site-years):87 site-years before, 33 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Dec 08, 2014
Comments:CMF of shifting the left-turn lane further away from the adjacent through lane and result in a less negative offset or no offset.