CMF / CRF Details

CMF ID: 5535

Shorten left turn lane by X percent at unsignalized median opening

Description: Shorten left turn lane by X percent shorter than the Greenbook recommended length at unsignalized median openings.

Prior Condition: Turn lane X percent different than Greenbook recommended length

Category: Access management

Study: Safety Impacts of Using Short Left-Turn Lanes at Unsignalized Median Openings, Chen et al., 2014

 
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Crash Modification Factor (CMF)
Value: Equation
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value: Equation
Adjusted Standard Error:
Unadjusted Standard Error:
Applicability
Crash Type: Fixed object,Rear end,Sideswipe
Crash Severity: All
Roadway Types: Not specified
Number of Lanes: 4 to 8
Road Division Type: Divided by Median
Speed Limit: 30-40 mph
Area Type: Urban
Traffic Volume: Minimum of 6600 to Maximum of 64800 Average Daily Traffic (ADT)
Average Traffic Volume:
Time of Day: All
If countermeasure is intersection-based
Intersection Type:
Intersection Geometry:
Traffic Control:
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used: 2006 to 2011
Municipality: Houston
State: TX
Country: USA
Type of Methodology Used: Regression cross-section
Sample Size (crashes): 32 crashes
Sample Size (sites): 52 sites
Sample Size (site-years): 312 site-years
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Aug-12-2014
Comments: In the CMFunction, X is the percentage shorter than the Greenbook recommended length. Values spanned from -47% (i.e., 47% shorter than the Greenbook length) to 38% (i.e., 38% longer than the Greenbook length). Also, traffic volumes ranged from 1639 vpdpl to 10,805 vpdpl.