Area Condition Score
The Area Condition Score is a composite neighborhood-level risk signal answering: which parts of San Francisco show the strongest constellation of conditions associated with elevated overdose risk? It measures social and environmental precursors that research has shown to precede overdose concentration — not overdoses directly.
v1.0 component weights are derived from peer-reviewed literature and documented in the methodology. Empirical validation against SF OCME census-tract mortality data is planned for v1.1.
| Component | Weight | Evidence Basis |
|---|---|---|
| SRO housing density | 0.20 | Rowe et al. 2019 — 19.3× mortality elevation (PMID 31581024) |
| EMS overdose call density | 0.20 | Direct observed demand signal — SFFD Dispatch (DataSF) |
| 311 complaint composite | 0.18 | Li et al. 2020 — code violation 0.92, public health 0.89, street lighting 0.83 (DOI 10.1038/s41598-020-76685-z) |
| Social Vulnerability Index | 0.15 | CDC/ATSDR SVI 2022 — 16-variable nationally validated composite |
| Business closure rate | 0.12 | Athens et al. 2020 urban blight-health nexus (PMID 32645013) |
| Rent velocity index | 0.08 | Displacement/gentrification as overdose risk precursor — Fink et al. 2024 systematic review |
| CalEnviroScreen 4.0 score | 0.05 | OEHHA CalEnviroScreen 4.0 — 21-indicator validated CA composite |
| Residential vacancy rate | 0.02 | Athens et al. 2020; Choi et al. 2022 Cincinnati spatial clustering |
EMS Effectiveness Score
The EMS Effectiveness Score measures the alignment between observed EMS system capacity and overdose demand across geographic areas. It is explicitly not a unit performance evaluation, not an individual responder assessment, and not a basis for disciplinary action. It is a system-level signal: where is there a measurable gap between where overdoses are occurring and where EMS resources are reaching them effectively?
EES outputs require 30-day SFFD/DPH leadership preview before publication. Enforced at the API endpoint layer. Every EES response carries the mandatory signal disclaimer. Outputs describe system conditions — not unit, station, or individual performance.
Naloxone Coverage Score
The Naloxone Coverage Score maps the spatial relationship between naloxone access points and overdose call density. It identifies coverage deserts — areas where overdose risk is elevated but naloxone access within walkable distance is absent.
Research in SF (Rowe et al. 2016) and Baltimore (Yi et al. 2022) demonstrates that physical proximity to naloxone distribution sites is significantly and inversely associated with overdose mortality. The NCS operationalizes this as a resource alignment diagnostic: not who is distributing naloxone, but where coverage is insufficient relative to demand.
PSH Community Signal Score
The PSH Community Signal Score measures observable changes in EMS, police, and 311 service patterns around a permanent supportive housing facility before and after opening. It does not evaluate operator quality, resident behavior, or program success. It describes what is publicly observable from city service data.
Pre-publication review by DPH and the housing operator is an architectural requirement enforced at the API layer — not a policy preference.
PCSS endpoints return pending_review status until a 30-day review window has elapsed and review completion is logged in the database. No PCSS output reaches any user before review completion. No exceptions.
Synthetic Threat Index
The Synthetic Threat Index is the only MERIDIAN module that generates real-time alerts, and the only one designed to anticipate conditions rather than describe them retrospectively. It addresses a documented gap: San Francisco identified its first cychlorphine death post-mortem.