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: 3 Stars   [View score details]
Crash Modification Factor (CMF)
Value: 0.64
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
Applicability
Crash Type: All
Crash Severity: All
Roadway Types: Principal Arterial Other Freeways and Expressways
Number of Lanes:
Road Division Type:
Speed Limit:
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:
Municipality:
State: CA
Country: USA
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.