CMF / CRF Details

CMF ID: 8341

Widen shoulder


Prior Condition: Freeway with narrower left shoulder

Category: Shoulder treatments

Study: Operational and Safety Trade-offs: Reducing Freeway Lane and Shoulder Width to Permit an Additional Lane, Dixon et al., 2016

Star Quality Rating: 3 Stars   [View score details]
Rating Points Total: 80
Crash Modification Factor (CMF)
Value: 0.95
Adjusted Standard Error:
Unadjusted Standard Error: 0.021
Crash Reduction Factor (CRF)
Value: 5   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error: 2.1
Crash Type: All
Crash Severity: All
Roadway Types: Principal Arterial Other Freeways and Expressways
Street Type:
Minimum Number of Lanes: 2
Maximum Number of Lanes: 5
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather: Not specified
Road Division Type: Divided by Median
Minimum Speed Limit: 50
Maximum Speed Limit:
Speed Unit: mph
Speed Limit Comment: > = 50 mph
Area Type: Urban
Traffic Volume: Minimum of 200 to Maximum of 281450 Annual Average Daily Traffic (AADT)
Average Traffic Volume: 152163 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: 2010 to 2013
Municipality: Dallas, Houston, San Antonio
State: TX
Country: USA
Type of Methodology Used: Regression cross-section
Sample Size (crashes): 2202 crashes
Sample Size (sites): 536 sites
Sample Size (site-years): 2144 site-years
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Jan-17-2017
Comments: CMF applies to increasing left shoulder by 1 foot.