CMF / CRF Details

CMF ID: 4020

Convert frontage road from two-way operation to one-way operation

Description: Convert frontage road from two-way operation to one-way operation

Prior Condition:  frontage road with two-way operation

Category: Access management

Study: Safety and Economic Impacts of Converting Two-way Frontage Roads to One-way: Methodology and Findings, Eisele et al., 2011

Star Quality Rating:2 Stars  [View score details]
Rating Points Total:60
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Reduction Factor (CRF)
Value:77  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:
Crash Type:Angle,Head on,Left turn
Crash Severity:All
Roadway Types:Not Specified
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:
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit:
Speed Limit Comment:
Area Type:Not specified
Traffic Volume:
Average Traffic Volume:
Time of Day:All
If countermeasure is intersection-based
Intersection Type:Other
Intersection Geometry:Not specified
Traffic Control:
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :2996 Average Daily Traffic (ADT)
Average Minor Road Volume :
Development Details
Date Range of Data Used:1998 to 2007
Type of Methodology Used:Simple before/after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Jun 04, 2012
Comments:This CMF is for non-PDO angle and opposite-direction crashes including a left-turning vehicle at interchange intersections. An interchange intersection is defined as a location where “the frontage roads intersects a cross street” (p. 28). They may be signalized or unsignalized. An interchange intersection is not the intersection of a frontage road and a ramp because there is a separate category of intersections known as ramp intersections with that configuration (p. 30). The CMF standard error was computed using the confidence interval given in Table 4.9 (p. 53): (CMF upper limit-CMF lower limit)/(2*1.96). The crash data consisted of records from 1998 to 2007 but excluded records from 2002 (p. 24). The study method was before-after with comparison group. Since this is not available on the list for study methodology, simple before-after was selected. The before and after sample sizes were computed using Table 4-5 (p. 48) which lists the annual crash frequency in the before and after periods and Table 3-4 (p. 36) which lists the duration of the before and after periods. The average ADT for the before and after period for each mainline treatment segment is given in Table 4-7 (p. 49); however, the overall average ADT for the group of mainline treatment segments is not provided. To compute the overall average ADT for the mainline, a weighted average was taken using the treatment segment average ADTs and the treatment site before and after period lengths listed in Table 3-4 (p. 36): 44*2200+60*1800+43*1800+60*2200+36*4600+60*5500+36*2600+60*3200/(44+60+43+60+36+60+36+60)=2996 -----------The star rating for this CMF was modified from 2 to 3 stars in January 2015. The previous star rating was assigned using a sample size score based only on the crashes in the period after the countermeasure installation. The standard scoring method in the Clearinghouse is to score the sample size based on the crashes before the countermeasure installation plus the expected crashes in the after period.