The Safety Priority Index System is a method originally developed in 1986 by the Oregon Department of Transportation (ODOT) for identifying potential safety problems on state highways. SPIS complies with the Federal Highway Safety Improvement Program (HSIP) and has been accepted by the Federal Highway Administration (FHWA) as fulfilling the requirements of the HSIP.  
 
When Oregon began developing its Safety Management System in response to the 1991 ISTEA, it identified SPIS as one of several essential building blocks.  SPIS has been recognized as an effective problem identification tool for evaluating state highways for segments with higher crash histories.
 
Several modifications to SPIS have been implemented over the years.  Following the study, “An Evaluation of the Safety Priority Index System (SPIS),” completed by Dr. Robert Layton of the Transportation Research Institute at Oregon State University modifications were implemented in the 1998 SPIS reports.  In 2005 the programs were rewritten in response to changes to the Crash Database, improvements to the reports were incorporated.  It is expected to rewrite the SPIS programs again in 2009 to include all public roads in Oregon (not just state highways).  

Additionally in 2010 ODOT undertook adding off-state highways (city and county roads) to the SPIS.  Originally the SPIS only include state highways. A process was developed and piloted in 2012 to include both on-state and off-state highways into SPIS using a Geographic Information System as a basis for SPIS process.  ODOT was able to calculate SPIS values for most of the functionally classed roads which include traffic volume information.  So not all public roads are included in the SPIS but most of the well traveled roads are included, all those that are functionally classed roads with traffic volumes attached.

 
The basic purpose of the SPIS program is to perform network screening on the state highway network and to identify and prioritize those sites that have promise as sites for potential safety improvements and merit further investigation. The process of conducting detailed engineering studies is an expensive one, therefore, only the sites with the highest ranking (top 5%) are investigated. The best candidates for safety projects will most likely be sites that rank high in terms of safety cost-effectiveness (see the Highway Safety Program Guide  for more information on project selection). SPIS Formulation 
 
Read documentation on how the SPIS is calculated. 
  

The following is documentation for the new GIS SPIS process:

 Introduction to SPIS 
 1- Sources of SPIS Data 
 2- Source of Annual SPIS Crash Data 
 3- SPIS ETL (Extract, Translate, and Load Data) Process 
 4- Annual SPIS Formulas 
 5- Annual SPIS Sliding Window 
 6- Using Annual SPIS 
 7- Annual SPIS Cut-off Values and Percentage Ranks 
 8- Understanding Annual SPIS Reports 
 9- On-State Segment Length Discrepancy 
 10- OASIS Introduction 
 11- OASIS Data 
 12- OASIS General Settings 
 13- OASIS Crash Conditions 
 14- OASIS Equations 
 15- OASIS Reports 
 16- Crash Summary Report 
 A1- Appendix – SPIS Glossary 
 A2- Appendix – SPIS Available Resources 

 
Also included for reference is the following:

Read Frequently Asked Questions about SPIS.
 
Also here is a link to the SPIS Calculator Tool in excel.
 
View this PowerPoint Presentation explaining GIS SPIS.

SPIS reports are only available to authorized staff through the following link -

The SPIS reports are available to the public from the region contacts shown above.  Please contact the region contact for more information.

 
Each year, a list of the top 10% SPIS sites is generated and the top 5% sites are investigated by the five Region Traffic manager's offices. These sites are evaluated and investigated for safety problems. If a correctable problem is identified, a benefit/cost analysis is performed and appropriate projects are initiated, often with funding from the Highway Safety Improvement Program (HSIP).  Regions report the results of their site evaluations to the State Traffic Engineer.  These results are incorporated into the Highway Safety Improvement Program (HSIP) 5 percent report to FHWA by August 31 of each year. 

Under MAP 21 (Oct 2012) the requirement for reporting the top 5% sites was elimated, but ODOT continues to investigate the top 5% sites each year.