Use and Modification of Default SPFs in the IHSDM Mike Dimaiuta LENDIS Corporation

Options for using SPFs in IHSDM Use Default SPFs “as is” Calibrate models, including SPFs Enter and use “your own” SPFs

Use Default SPFs “as is” Run IHSDM Crash Prediction Module (CPM) without calibrating (i.e. with calibration factors = 1.0)

Use Default SPFs

Use Default SPFs “as is”

Calibrate Models / SPFs Follow HSM Part C calibration procedure and enter factors via IHSDM Administration Tool

Calibrate Models / SPFs

Calibrate model / SPFs

Enter and use “your own” SPFs Via the IHSDM Administration Tool: – “Crash Prediction” > “Model Data Sets”

Enter and use “your own” SPFs Capabilities: – For all SPFs, can change: Regression coefficients Overdispersion parameters Limitation: – Can not change SPF functional form

Enter and use “your own” SPFs After editing data, save as a new Model Data Set “configuration” and select when running CPM

Enter and use “your own” SPFs Example: Multilane Rural H’way – Estimate crashes using defaults – Enter “My State’s SPFs” into Administration Tool – Run CPM with modified SPFs to generate and compare results

Estimate crashes using default SPFs

Enter “My State’s” SPFs into Administration Tool

Run CPM with modified SPFs

Compare Results Estimated Total crashes using default SPFs: Estimated Total crashes using “My State’s” SPFs:27.62

Summary No requirement for agencies to develop their own SPFs for IHSDM, but… IHSDM provides a mechanism for agencies to edit all default SPFs (coefficients and overdispersion parameters only) Either way can produce good results!

Questions? For additional information: IHSDM Technical Support: To download IHSDM software: Shyuan-Ren (Clayton) Chen (202)