CMF / CRF Details

CMF ID: 8002

Install left-turn lane at signalized intersection


Prior Condition:  Intersections without left turn lanes

Category: Intersection geometry

Study: Safety Evaluation of Signal Installation With and Without Left Turn Lanes on Two Lane Roads in Rural and Suburban Areas, Srinivasan et al., 2014

Star Quality Rating:4 Stars  [View score details]
Rating Points Total:115
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.079
Crash Reduction Factor (CRF)
Value:58.8  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:7.9
Crash Type:Rear end
Crash Severity:All
Roadway Types:Not specified
Street Type:
Minimum Number of Lanes:2
Maximum Number of Lanes:2
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:All
If countermeasure is intersection-based
Intersection Type:Not specified
Intersection Geometry:3-leg
Traffic Control:Signalized
Major Road Traffic Volume:Minimum of 2981 to Maximum of 18248 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 972 to Maximum of 13880 Annual Average Daily Traffic (AADT)
Average Major Road Volume :9199 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :4847 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used:1992 to 2012
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (crashes):207 crashes before, 188 crashes after
Sample Size (sites):36 sites before, 36 sites after
Sample Size (site-years):180 site-years before, 174 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Nov 10, 2016
Comments:The CMF was developed for both rural and suburban areas. 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.