Logic chain (never skip a link)
Documented crash pattern → contributing factors → candidate treatments targeting THAT pattern → effectiveness (CMF w/ star rating, crash type, base condition) → feasibility/cost → recommendation.
Selection sources
FHWA Resources Proven Safety Countermeasures · PEDSAFE/BIKESAFE selectors · CMF Clearinghouse · NCHRP syntheses.
Free companions
FHWA Proven Safety Countermeasures — the canonical starting menu: 28 countermeasures, each with its own page (effectiveness/CRFs, context, cost), a filter tool, and a free booklet. Start every pattern→treatment search here before touching the Clearinghouse.
CMF math
Expected crashes × CMF = after; multiple CMFs multiply only if independent (be conservative; agencies often cap combined reduction) #status/verify local policy.
B/C sketch
Annual benefit = Σ(reduced crashes by severity × crash cost figures — use FDOT/agency-accepted values #status/verify); compare to annualized cost.
Write-up pattern
“Pattern X (n=, % of total, K+A=) is addressed by [treatment], an FHWA Proven Safety Countermeasure with CMF ___ (★★★★, [crash type]) [cite ID].”
Practice question
Corridor is 60% rear-end at signals — why is a raised median the wrong first answer, and what’s a better-matched menu?
QA/QC reminder
Every CMF quoted has ID, star rating, crash type, and comparable context — or it’s out.