CMF / CRF Details

CMF ID: 10755

Install TWLTL (two-way left turn lane) on four lane road

Description: Converting 4-lane road to 4-lane plus one two-way turning lane.

Prior Condition:  Undivided roadway

Category: Roadway

Study: Context-based Crash Modification Factors for Medians on Rural Four-Lane Roadways: A Bayesian Approach, Li et al., 2021

Star Quality Rating:2 Stars  [View score details]
Rating Points Total:50
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Type:All
Crash Severity:All
Roadway Types:Principal Arterial Other
Street Type:
Minimum Number of Lanes:4
Maximum Number of Lanes:4
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:Undivided
Minimum Speed Limit:55
Maximum Speed Limit:65
Speed Unit:mph
Speed Limit Comment:
Area Type:Rural
Traffic Volume:Minimum of 3000 to Maximum of 24000 Annual Average Daily Traffic (AADT)
Average Traffic Volume:8457 Annual Average Daily Traffic (AADT)
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:2013 to 2018
Type of Methodology Used:
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Jul 01, 2021
Comments:Applies to the addition of a two-way left-turn lane (TWLTL) to a four-lane undivided highway.