6.2.7 Comparison of Predictive Safety Analysis Tools

The HSM Spreadsheets were developed as part of the NCHRP Project 17-38 to implement the HSM Part C predictive methods for rural twolane two-way roads, rural multilane highways, and urban and suburban arterials.
IHSDM is typically used more frequently by practitioners for analysis of complex or larger projects. Segmentation is automated if LandXML files are available to import. The crash module for the IHSDM includes a "sitebased analysis tool" that can be used without having to include the detailed horizontal and vertical alignment and cross-section data.
ISATe is a spreadsheet-based tool that implements the HSM predictive methods for freeways and ramps. Its application is very similar to the developed HSM Spreadsheets.
The SPICE tool was developed to evaluate the anticipated safety performance of intersection control strategies within a single tool. The SPICE Tool uses the SPFs in Part C of the HSM (and subsequent NCHRP Reports) to select high-quality CMFs from Part D of the HSM and CMF Clearinghouse. The SPICE tool automates many of the decisions necessary for selecting the appropriate SPF or CMF to apply. The SPICE Tool only provides predicted crash frequencies and severities for intersections. The SPICE Tool is not intended to replace the functionality of other tools, including the HSM spreadsheets, ISATe, or IHSDM.
The HSS performs crash prediction evaluations in roadway facilities based on the HSM Part C crash prediction models. SPF and the CMFs are presented for the various facility types. HSS can conduct a standalone evaluation of a segment and intersection or analyze corridors composed of a series of segments and intersections. Each of the crash prediction tools is considered to faithfully implement the HSM Part C crash prediction models. The difference between these various tools is in their approach to allow the user to input the data needed to run the predictive analysis.
FHWA requirements surrounding predictive crash analysis only apply in situations to which the predictive tool can analyze the project.
A summary of the predictive safety analysis tools is shown in . This table shows the types and applications of predictive safety tools.
Table 6-5: Predictive Safety Analysis Tools
Analysis Tool
Application
HSM spreadsheets
  • Rural two-lane roads
  • Rural multilane highways
  • Urban and suburban arterials
IHSDM
  • Roadway facilities found in HSM Part C
  • Complex or large projects
  • New research conducted since HSM
ISATe
  • Freeways
  • Freeway ramps
  • Interchanges
  • C-D Roads
SPICE
  • Intersections
HSS
  • Roadway facilities found in HSM Part C