How We Calculate the Maritime Safety Score
A transparent look at the data and math behind every score on Ship Tea.
The Maritime Safety Score is a composite rating from 0 to 100 that reflects a cruise ship's overall safety and compliance posture. It draws from five independent federal data sources, each covering a different dimension of maritime safety. By combining inspection results, incident records, sanitation scores, crime statistics, and investigation findings into a single number, the score gives passengers a clear, data-driven way to compare ships before booking.
Every component is weighted to reflect its relative importance to passenger safety, and each uses time-decay functions so that recent performance matters more than distant history. Below, we break down exactly how each component works.
Score Components & Weights
| Component | Weight | Source | What It Measures |
|---|---|---|---|
| Inspection Health | 35% | USCG PSIX | Deficiency records, severity tiers, operational controls |
| Incident History | 25% | USCG MISLE | Marine casualties, injuries, property damage |
| CDC Sanitation | 20% | CDC VSP | Vessel Sanitation Program inspection scores |
| Crime Rate | 10% | DOT CVSSA | Cruise vessel crime per-passenger-day rates |
| Major Investigations | 10% | NTSB | Marine safety investigation findings |
Scoring Scale
The final composite score maps to one of four rating tiers. These tiers provide a quick visual reference for how a ship compares to the fleet.
Inspection Health (35%)
This component reflects the results of U.S. Coast Guard Port State Information Exchange (PSIX) inspections. Each ship starts at a perfect score of 100, and points are deducted for every recorded deficiency based on its severity tier:
- Critical — -8 points per deficiency
- High — -5 points per deficiency
- Medium — -3 points per deficiency
- Low — -1 point per deficiency
Several modifiers adjust the impact of deficiencies:
- Unresolved past due — Penalty is doubled (2x multiplier) for deficiencies that remain open past their correction deadline.
- Active operational controls — An additional -15 points per active operational control imposed on the vessel.
- Repeat deficiencies — A 1.5x multiplier applies when the same deficiency type appears in consecutive inspection cycles.
Older deficiencies carry less weight: the penalty decays by 50% per year so that a deficiency from three years ago has only one-eighth of its original impact. The lookback window is five years. The component score has a floor of 0 and cannot go negative.
Incident History (25%)
This component uses marine casualty data from the USCG Marine Information for Safety and Law Enforcement (MISLE) system. Each ship starts at 100, and points are deducted based on the type of incident:
- Fatality — -25 points per event
- Serious injury — -15 points per event
- Minor injury — -8 points per event
- Property damage exceeding $75,000 — -10 points per event
- Grounding or loss of propulsion — -5 points per event
As with inspections, incident penalties decay by 50% per year so that a serious injury five years ago carries far less weight than one last month. The lookback window is ten years, and the component score has a floor of 0.
CDC Sanitation (20%)
This component incorporates the CDC's Vessel Sanitation Program (VSP) inspection scores, which are already on a 0-100 scale. Rather than using a single inspection, we apply a weighted-recency model across the three most recent inspections:
- Most recent inspection — 60% weight
- Second most recent — 25% weight
- Third most recent — 15% weight
Two additional penalty adjustments apply to this component. A failed inspection (any score below 86) triggers a -10 point deduction for each failure. If the ship has an active gastrointestinal illness outbreak at the time of scoring, a further -15 point penalty is applied.
Crime Rate (10%)
This component draws on quarterly crime statistics published by the Department of Transportation under the Cruise Vessel Security and Safety Act (CVSSA). The per-passenger-day crime rate for each cruise line is compared against the industry average:
- Below industry average — 100 points
- At industry average — 85 points
- 1.5x the industry average — 70 points
- 2x or more the industry average — 50 points
Because CVSSA data is reported at the cruise-line level rather than per ship, this score is applied uniformly to all ships operated by the same line. Values between the thresholds listed above are interpolated linearly.
Major Investigations (10%)
The final component accounts for major safety investigations conducted by the National Transportation Safety Board (NTSB). Each ship starts at 100, and deductions are applied based on the status of any associated investigations:
- Open or recent investigation — -20 points per investigation
- Closed investigation — -10 points per investigation
Investigation penalties follow the same 50% annual decay curve used by other components, ensuring that older investigations diminish in impact over time. The lookback window is ten years, and the component score has a floor of 0.
Data Sources & Freshness
The Maritime Safety Score relies entirely on publicly available federal datasets. Here is where each component's data comes from and how often it is updated:
| Data Source | Agency | Update Frequency |
|---|---|---|
| Port State Information Exchange (PSIX) | U.S. Coast Guard | Updated after each inspection |
| Marine Information for Safety and Law Enforcement (MISLE) | U.S. Coast Guard | Updated as incidents are reported |
| Vessel Sanitation Program (VSP) | CDC | Updated after each inspection cycle |
| Cruise Vessel Security and Safety Act (CVSSA) Reports | Department of Transportation | Published quarterly |
| Marine Safety Investigations | NTSB | Updated as investigations progress |
Ship Tea pulls the latest available data from each source and recalculates every Maritime Safety Score on a weekly basis. When a new inspection, incident, or report is published, it will be reflected in the score within seven days.
Transparency
The Maritime Safety Score is entirely data-driven. No editorial opinion, sponsorship, or subjective judgment influences the result. Every data point used in the calculation comes from publicly accessible federal databases maintained by the U.S. Coast Guard, CDC, Department of Transportation, and NTSB.
We believe passengers deserve clear, honest information about the ships they sail on. If you have questions about the methodology or spot a data discrepancy, we welcome feedback.