CMF / CRF Details

CMF ID: 7974

Install a traffic signal and left turn lanes

Description: Install a traffic signal and left turn lanes

Prior Condition:  Intersections with a stop sign on minor roads

Category: Intersection traffic control

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:112
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.066
Crash Reduction Factor (CRF)
Value:51.3  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:6.6
Crash Type:Other
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:Stop-controlled
Major Road Traffic Volume:Minimum of 2981 to Maximum of 18248 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 1852 to Maximum of 13880 Annual Average Daily Traffic (AADT)
Average Major Road Volume :10169 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :5970 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):157 crashes before, 76 crashes after
Sample Size (sites):19 sites before, 19 sites after
Sample Size (site-years):95 site-years before, 91 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. CMF applies to frontal impact crashes, including 1) left turn same roadway, 2) left turn different roadway, and 3) angle.