CMF / CRF Details

CMF ID: 4674

Decrease freeway ramp spacing from infinity to S (ft) with/without auxiliary lane

Description: Decreasing ramp spacing (painted gore to painted gore) on freeway segments from infinity to S (ft) with or without exisiting auxiliary lane

Prior Condition:  Ramp spacing approaching infinity, which represents a basic freeway segment with no ramps.

Category: Access management

Study: Safety Evaluation of Geometric Design Criteria for Entrance-Exit Ramp Spacing and Auxiliary Lane Use, Le, T. Q., and Porter, R. J., 2012

Image: View the countermeasure image.

Star Quality Rating:4 Stars  [View score details]
Rating Points Total:125
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Type:Not specified
Crash Severity:All
Roadway Types:Principal Arterial Interstate
Street Type:
Minimum Number of Lanes:
Maximum Number of Lanes:
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:Divided by Median
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit:
Speed Limit Comment:
Area Type:Not specified
Traffic Volume:Minimum of 5,134 to Maximum of 153,500 Average Daily Traffic (ADT)
Average Traffic Volume:43,158 Average Daily Traffic (ADT)
Time of Day:Not specified
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 2008
Type of Methodology Used:Regression cross-section
Sample Size (site-years):1212 site-years
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:May 01, 2013
Comments:- CMF is function of ramp spacing (S) in ft. and existence of auxiliary lane (Auxln = 0 or 1)- See Studay possible bias for limitations.