CMF / CRF Details

CMF ID: 256

Provide a channelized left-turn lane on both major-road approaches

Description:

Prior Condition: No Prior Condition(s)

Category: Intersection geometry

Study: Handbook of Road Safety Measures, Elvik, R. and Vaa, T., 2004

 
Star Quality Rating: 3 Stars   [View score details]
Rating Points Total: 75
Crash Modification Factor (CMF)
Value: 0.96
Adjusted Standard Error: 0.21
Unadjusted Standard Error: 0.12
Crash Reduction Factor (CRF)
Value: 4   (This value indicates a decrease in crashes)
Adjusted Standard Error: 21
Unadjusted Standard Error: 12
Applicability
Crash Type: All
Crash Severity: A (serious injury),B (minor injury),C (possible injury)
Roadway Types: Not Specified
Number of Lanes: 2
Road Division Type:
Speed Limit:
Area Type: Rural
Traffic Volume:
Average Traffic Volume:
Time of Day:
If countermeasure is intersection-based
Intersection Type: Roadway/roadway (not interchange related)
Intersection Geometry: 4-leg
Traffic Control: Not Specified
Major Road Traffic Volume: Minimum of 5000 to Maximum of 15000 Average Daily Traffic (ADT)
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:
Municipality:
State:
Country:
Type of Methodology Used: 9
Other Details
Included in Highway Safety Manual? Yes. HSM lists this CMF in italics font to indicate that it has a lower reliability than bold font CMFs since it has an adjusted standard error of 0.2 to 0.3. HSM also includes an asterisk (*) to indicate that the CMF value itself is within the range 0.90 to 1.10, but that the confidence interval defined by the CMF ± two times the standard error may contain the value 1.0. This is important to note since a treatment with such an CMF could potentially result in (a) a reduction in crashes (safety benefit), (b) no change, or (c) an increase in crashes (safety disbenefit). HSM recommends that this CMF should be used with caution.
Date Added to Clearinghouse: Dec-01-2009
Comments: Countermeasure name changed from "physical channelization of left-turn lane on major road" to match HSM.