worldmonitor/docs/methodology/chokepoints.mdx

---
title: "Chokepoint Methodology"
description: "How World Monitor scores 13 monitored maritime chokepoints, including the seven-item live-flow subset backed by EIA energy baseline volumes."
---

## What we track

WorldMonitor has **13 monitored waterways** in the canonical chokepoint registry and the
`GetChokepointStatus` RPC. The status RPC returns one row for each canonical id:
`suez`, `malacca_strait`, `hormuz_strait`, `bab_el_mandeb`, `panama`,
`taiwan_strait`, `cape_of_good_hope`, `gibraltar`, `bosphorus`,
`korea_strait`, `dover_strait`, `kerch_strait`, and `lombok_strait`.

Only **seven** of those 13 currently carry a live oil/gas flow estimate from
`energy:chokepoint-flows:v1`, because only those seven have an EIA baseline id
in the current seeder:

| Canonical id | Public name | EIA baseline id | Baseline flow (mb/d) |
|---|---|---|---:|
| `hormuz_strait` | Strait of Hormuz | `hormuz` | 21.0 |
| `malacca_strait` | Strait of Malacca | `malacca` | 17.2 |
| `suez` | Suez Canal / SUMED | `suez` | 7.6 |
| `bab_el_mandeb` | Bab el-Mandeb | `babelm` | 6.2 |
| `dover_strait` | Dover Strait | `danish` | 3.0 |
| `bosphorus` | Bosporus Strait | `turkish` | 2.9 |
| `panama` | Panama Canal | `panama` | 0.9 |

The other six canonical waterways still receive transit summaries, warnings,
AIS-disruption matching, threat classification, disruption score, and war-risk
tier, but `flowEstimate` is absent until a baseline-backed flow model is added.

## Live Flow

Live flow is computed by `scripts/seed-chokepoint-flows.mjs` on the seven-item
subset above:

1. Read PortWatch history from `supply_chain:portwatch:v1`.
2. Choose the signal: use `capTanker` deadweight tonnage when at least half of
   the prior-window days have DWT coverage; otherwise use tanker counts.
3. Compute `current7d` as the average of the latest seven days.
4. Compute `baseline90d` as the average of the previous window, up to 90 days
   (`history.slice(-97, -7)`), requiring at least 20 baseline days.
5. Compute `flowRatio = clamp(current7d / baseline90d, 0, 1.5)`.
6. Compute `currentMbd = baselineMbd * flowRatio`, rounded to one decimal.

The published ratio is therefore a recent 7-day average against a prior
up-to-90-day rolling baseline. The `baselineMbd` field is the annual EIA 2023
reference level; it is used to convert the observed ratio into mb/d. Flow ratios
can publish from 0% to 150% of baseline after the clamp.

Live flow is eligible only when the PortWatch series has at least 40 total days
of history. After that gate, the seeder still requires at least three recent
days, at least 20 prior-window baseline days, and a non-thin baseline: at least
1 DWT-day when using tanker deadweight tonnage, or at least 0.5 tanker-count
when using vessel counts. Rows below those floors are omitted rather than
reported as zero flow.

The `disrupted` boolean is separate from the color badge: it is true when each
of the latest three individual days is below 85% of the same `baseline90d`.

Each published flow estimate may also include live hazard context from
`portwatch:disruptions:active:v1`. The seeder looks for the nearest active
GDACS `RED` or `ORANGE` alert within 500 km of the supported chokepoint and
surfaces it as `hazardAlertLevel` and `hazardAlertName`. This is annotation
only: hazard enrichment does not change `currentMbd`, `flowRatio`, or the
`disrupted` calculation.

## Score Badge

The public `status` field on `ChokepointInfo` is a traffic-light score badge:
`green`, `yellow`, or `red`. It is not an operational closure-state label.

The score is:

```text
disruptionScore = min(
  100,
  threatLevelWeight + warningComponent + aisComponent + anomalyBonus
)
```

Where:

- `threatLevelWeight` is the geopolitical baseline weight in the taxonomy below.
- `warningComponent = min(15, activeWarnings * 5)`.
- `aisComponent = min(15, maxCongestionSeverity * 5)`, where low/elevated/high
  AIS congestion severity maps to 1/2/3.
- `anomalyBonus = 10` only when transit history shows a 50% or larger traffic
  drop against the prior 30-day transit-count baseline and the threat level is
  `war_zone` or `critical`.

The score badge thresholds are:

| Score range | `status` |
|---:|---|
| `< 20` | `green` |
| `20-49` | `yellow` |
| `>= 50` | `red` |

## Threat Taxonomy

The geopolitical threat baseline is assigned per chokepoint in
`server/worldmonitor/supply-chain/v1/get-chokepoint-status.ts` and weighted in
`server/worldmonitor/supply-chain/v1/_scoring.mjs`.

| Threat level | Weight | Meaning |
|---|---:|---|
| `war_zone` | 70 | Active naval conflict, blockade, or strait closure |
| `critical` | 40 | Active attacks on commercial shipping |
| `high` | 30 | Military seizure risk or armed escort zone |
| `elevated` | 15 | Military tensions or disputed waters |
| `normal` | 0 | No significant military threat |

Current assignments:

| Canonical id | Public name | Threat level | Weight | War-risk enum |
|---|---|---|---:|---|
| `suez` | Suez Canal | `high` | 30 | `WAR_RISK_TIER_HIGH` |
| `malacca_strait` | Strait of Malacca | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `hormuz_strait` | Strait of Hormuz | `war_zone` | 70 | `WAR_RISK_TIER_WAR_ZONE` |
| `bab_el_mandeb` | Bab el-Mandeb | `critical` | 40 | `WAR_RISK_TIER_CRITICAL` |
| `panama` | Panama Canal | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `taiwan_strait` | Taiwan Strait | `elevated` | 15 | `WAR_RISK_TIER_ELEVATED` |
| `cape_of_good_hope` | Cape of Good Hope | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `gibraltar` | Strait of Gibraltar | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `bosphorus` | Bosporus Strait | `elevated` | 15 | `WAR_RISK_TIER_ELEVATED` |
| `korea_strait` | Korea Strait | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `dover_strait` | Dover Strait | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |
| `kerch_strait` | Kerch Strait | `war_zone` | 70 | `WAR_RISK_TIER_WAR_ZONE` |
| `lombok_strait` | Lombok Strait | `normal` | 0 | `WAR_RISK_TIER_NORMAL` |

## Transit Anomaly

Transit anomaly detection for `anomalyBonus` is based on compact transit-count
history, not the live mb/d flow model. It compares the latest seven transit
counts with the preceding 30 days converted to a seven-day baseline:

```text
baselineAvg7 = (sum(days -37..-8) / availableBaselineDays) * 7
dropPct = round((baselineAvg7 - recent7) / baselineAvg7 * 100)
signal = dropPct >= 50 AND threatLevel in {war_zone, critical}
```

If signalled, the handler appends a description such as
`Traffic down 55% vs 30-day baseline, vessels may be transiting dark (AIS off)`.
The anomaly path is gated before that comparison: it requires at least 37 days
of compact transit-count history, and the normalized seven-day baseline must be
at least 14 transits. Thin baselines return no anomaly signal.

## Country Exposure

`GetCountryChokepointIndex` returns a separate exposure model for a country and
HS2 chapter. It is PRO-gated and cached at
`supply-chain:exposure:{ISO2}:{HS2}:v1`.

When bilateral HS4 import products are available, exposure is computed as:

```text
productWeight = product.totalValue / totalSectorValue
routeCoverage = overlappingRouteIds / chokepoint.routeIds.length
contribution = routeCoverage * exporter.share * productWeight * 100
```

Contributions are summed per chokepoint across matching products and top
exporters. For HS2 `27`, chokepoints with `shockModelSupported = true` receive a
1.5x energy-model boost capped at 100.

When bilateral product data is unavailable, the fallback score is:

```text
exposureScore = overlappingCountryRouteIds / chokepoint.routeIds.length * 100
```

with the same HS2 `27` supported-energy boost and 100 cap. The
`vulnerabilityIndex` is the weighted top-three score:

```text
top1 * 0.5 + top2 * 0.3 + top3 * 0.2
```

## Provenance

Chokepoint status combines Redis-backed transit summaries, flow estimates,
navigational warnings, AIS disruption matching, and the static threat taxonomy.
If a canonical chokepoint lacks upstream transit coverage for the current cycle,
`transitSummary.dataAvailable` is false and the response-level
`upstreamUnavailable` flag is set so clients can render partial-coverage UI.

Refresh cadence:

- `energy:chokepoint-flows:v1`: Railway seed loop every 6 hours.
- `supply_chain:chokepoints:v4`: status warm-ping every 30 minutes.
- `supply_chain:transit-summaries:v1`: AIS relay compact transit summary.

## Known Limits

- The seven live-flow rows are energy-baseline-backed; the other six monitored
  waterways do not yet publish mb/d estimates.
- The Dover Strait live-flow row currently maps to the EIA `danish` baseline id.
  Treat `baselineMbd` as the source reference and `id` as the canonical
  WorldMonitor row id.
- AIS and PortWatch coverage can degrade near heavily jammed or conflict-heavy
  regions. Missing upstream coverage is surfaced as unavailable data, not
  synthesized as zero traffic.
- Baselines are annual EIA reference levels used for mb/d conversion. The live
  ratio itself uses recent PortWatch observations against the prior rolling
  baseline window described above.

## Corrections

See [`/corrections`](/corrections) for the planned revision-log shape. If you
spot a wrong number today, open a GitHub issue at the
[public repository](https://github.com/koala73/worldmonitor/issues).