This document is a “how-to” guidebook for agencies that are developing jurisdiction-specific safety performance functions (SPFs). The guidebook discusses the statistical issues associated with the development of jurisdiction-specific SPFs and provides a step-by-step procedure that states can use to develop jurisdiction-specific SPFs. Statistical issues covered in this guidebook include:

• Over-dispersion.
• Selection of Explanatory Variables.
• Functional Form of the Model and Explanatory Variables.
• Over-fitting of SPFs.
• Correlation among Explanatory Variables.
• Homogenous Segments and Aggregation.
• Presence of Outliers.
• Endogenous Explanatory Variables.
• Estimation of SPFs for Different Crash Types and Severities.
• Goodness of Fit.

Intended users include safety practitioners, consultants, and researchers. Users are expected to have more than a basic understanding of statistics.