How to use SPF Clearinghouse

It is very simple to use SPF Clearinghouse. You can search reported SPFs by category (e.g., intersection, segment, ramps, etc.) or by keyword.

 

Search SPF

Search SPF:

It is very simple to use the SPF Clearinghouse. You can search reported SPFs by category (e.g., intersection, segment, etc.) or by keyword.

Each reported SPF contains the following:

  • The functional format of the SPF (e.g.,N=ea * AADTmajorb * AADTminorc)
  • Explanation of each variable (under “more information”)
  • Coefficient values for Fatal & Injury and Total crashes (e.g., a, b, c)
  • Overdispersion parameters (Fatal & Injury and Total crashes)
  • The author’s name (or the person who reported the SPF)
  • Web link to a research study (if available)
  • State/city data used to develop the SPF
  • Other information (e.g., goodness-of-fit values, Max/Min AADT, author contact information)

 A graphical representation of each SPF is provided. Graphs were plotted against a variable: AADT (any other variables were assumed to have the value = 1). 

When the SPF is known, a Predicted Average Crash Frequency can be calculated. 

The following information is needed to calculate a Predicted Average Crash Frequency (the example of an intersection is shown):

AADTmajor, AADTminor, coefficient values as well as Calibration Factor. Calibration Factor is needed to account for local conditions.

Report (Add) SPF

 

Before reporting any new SPF, please check if your SPF has already been reported. 

To add a new SPF, please follow the "Add SPF" link. Please fill in the required information. Make sure to give as much information as possible when reporting your SPF.

The SPF clearinghouse team will verify your SPF before it is added to our database.