CMF / CRF Details

CMF ID: 3340

Install variable speed limit signs

Description: Install variable speed limit signs

Prior Condition: No variable speed limit sign present

Category: Speed management

Study: Evaluation of Variable Speed Limits on I-270/I-255 in St. Louis, Bham et al., 2010


Star Quality Rating:	[View score details]

Crash Modification Factor (CMF)
Value:	0.92
Adjusted Standard Error:
Unadjusted Standard Error:

Crash Reduction Factor (CRF)
Value:	8 (This value indicates a decrease* in crashes)*
Adjusted Standard Error:
Unadjusted Standard Error:

Applicability
Crash Type:	All
Crash Severity:	All
Roadway Types:	Principal Arterial Interstate
Number of Lanes:
Road Division Type:
Speed Limit:	40 to 60
Area Type:	Urban
Traffic Volume:
Average Traffic Volume:
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:	2007 to 2009
Municipality:	St. Louis
State:	MO
Country:	U.S.A.
Type of Methodology Used:	Before/after using empirical Bayes or full Bayes
Sample Size (crashes):	1636 crashes after

Other Details
Included in Highway Safety Manual?	No
Date Added to Clearinghouse:	Jun-04-2012
Comments:	The crash count sum in Table S4 (p. 24) is for the 'after' period. The crash count for the 'before' period is not given. Although the crash count in the after period is substantial, the after period is only 1 year (p. 38); therefore, the crash count may give an inflated impression of the sample size. Traffic volume data is not given in this report. According to Table S2, the total length of the segments is 35.21 mi.

View the Full Study Details

Export Detail Page As A PDF

US Department of Transportation Federal Highway Administration

This site is funded by the U.S. Department of Transportation Federal Highway Administration
and maintained by the University of North Carolina Highway Safety Research Center

For more information, contact Karen Scurry at karen.scurry@dot.gov

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.