CMF / CRF Details

CMF ID: 5436

Install ramp meter

Description: Install a ramp meter signal at the on-ramp to enhance mainline throughput and reduce system-wide delay.

Prior Condition:  Freeway on-ramp with no ramp meter

Category: Advanced technology and ITS

Study: Ramp Metering Influence on Freeway Operational Safety near On-ramp Exits, Liu and Wang, 2013

Star Quality Rating:2 Stars  [View score details]
Rating Points Total:50
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.07
Crash Reduction Factor (CRF)
Value:36  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:7
Crash Type:All
Crash Severity:All
Roadway Types:Principal Arterial Other Freeways and Expressways
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:Urban
Traffic Volume:Minimum of 53500 to Maximum of 204000 Annual Average Daily Traffic (AADT)
Average Traffic Volume:130715 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:
Type of Methodology Used:Simple before/after
Sample Size (crashes):219 crashes before, 137 crashes after
Sample Size (sites):19 sites before, 19 sites after
Sample Size (site-years):57 site-years before, 57 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Jan 09, 2014
Comments:The CMF is based on a simple before-after analysis of the crash rate, which is defined as crashes per million vehicle interactions. The traffic volume reported above represents the two-way freeway volume.