Quantitative safety: SPFs (predicted crashes), Empirical Bayes (expected), CMFs to compare alternatives.
Why: moves you from “crashes happened” to “how many are expected, and what does treatment X buy?” — the language of HSIP funding and serious safety studies.
When:
- network screening
- countermeasure B/C
- before-after framing
- safety sections in alternatives analyses
Example questions:
- predicted vs expected vs observed?
- why EB-adjust before claiming a site is “high crash”?
Free companions
FHWA HSM Part C spreadsheets — free Excel tools that run the Part C predictive methods (predicted/expected crash frequency, EB, PSI) for rural two-lane, rural multilane, and urban/suburban arterials. The book is paywalled; this is how you actually run HSM analysis without buying software.
Related: CMF Clearinghouse · Countermeasure Selection and CMFs · How to Summarize 5-Year Crash Data