CMF / CRF Details

CMF ID: 8334

Install an additional lane

Description: Use reducing lane and shoulder width to install additional lanes for urban freeway

Prior Condition: Freeway with fewer lanes

Category: Roadway

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]
Crash Modification Factor (CMF)
Value: 0.76
Adjusted Standard Error:
Unadjusted Standard Error: 0.092
Crash Reduction Factor (CRF)
Value: 24   (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error: 9.2
Crash Type: All
Crash Severity: K (fatal),A (serious injury),B (minor injury),C (possible injury)
Roadway Types: Principal Arterial Other Freeways and Expressways
Number of Lanes: 2-5
Road Division Type: Divided by Median
Speed Limit: >50
Area Type: Urban
Traffic Volume: Minimum of 200 to Maximum of 281450 Average Daily Traffic (ADT)
Average Traffic Volume: 152163 Average Daily Traffic (ADT)
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): 407 crashes
Sample Size (sites): 536 sites
Sample Size (site-years): 2104 site-years
Other Details
Included in Highway Safety Manual? No
Date Added to Clearinghouse: Jan-17-2017
Comments: CMF applies to adding one additional lane with 11 ft average lane width


The information contained in the Crash Modification Factors (CMF) Clearinghouse is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in the CMF Clearinghouse. The information contained in the CMF Clearinghouse does not constitute a standard, specification, or regulation, nor is it a substitute for sound engineering judgment.