## 2 Materials and Methods
### Multi-Criteria Decision Analysis (MCDA)
#### 2.3.2 Evaluation Method and Set of Alternatives  
The method of evaluation is aligned with the assumptions and requirements of MCDA. The first two criteria are quantitative, while the remaining ones are qualitative. All criteria are maximized.  
Criterion C1 is expressed as a percentage. The authors determined that this criterion would have two thresholds: 50% (the indifference threshold) and 90% (the preference threshold). When comparing two alternatives, they are treated as equivalent if the difference in their values is below the indifference threshold (they receive a score of 0). If the difference falls between the two thresholds, a score is calculated using a linear scale ranging from 0 to 1. A difference exceeding the preference threshold automatically classifies one of the alternatives as the leading one, which then receives a value of 1 in the evaluation. Reductions in speed are observed during the voyage, which is considered normal operation. However, significant reductions may indicate an intention to perform specific maneuvers.  
A similar principle applies to changing courses. Criterion C2 is expressed in degrees. Following TSS routes (traffic separation scheme) forces ships to maintain specific headings. Course changes of smaller magnitude can be related to normal navigation, such as giving way to another ship. The authors set the indifference threshold at 30 degrees and the preference threshold at 60 degrees. The method of evaluation is analogous to that used for C1.  
Criteria C3-C8 are evaluated on a two-level yes/no scale. If the factor is present, the alternative receives 1 point; otherwise, it receives 0 points.  
Criterion C3 examines the ship's behavior in relation to applicable, region-specific traffic regulations. An alternative receives 1 point if the vessel's movement is non-compliant (e.g., entering a restricted navigation area), and 0 points if the movement complies with the rules. For the correctness of entering the destination port code (C4), an alternative receives 1 point if this information is inconsistent with the direction of traffic or voyage information, or if the information is missing. The alternative receives 1 point if there is a change in navigation status (C5) or a suspected mismatch in status. The disappearance of the AIS signal (C6) or the detection of a malfunctioning system results in the assignment of 1 point to the alternative. When abnormalities related to registration, flags, or certificates (C7) are detected for an alternative, 1 point is assigned. Similarly, if the ship receives a negative evaluation based on database records (C8), 1 point is assigned.  
The set of alternatives consists of several vessels operating in the study area. Thirteen sample vessels were selected for analysis (Table 2). Information about these vessels was simulated and based on realistic data. The simulated data reflect typical navigation scenarios. During navigation, ships perform various maneuvers, such as changing course, overtaking, or stopping. Some of these maneuvers may not comply with traffic regulations in a given water area. Additionally, ships may transmit incorrect signals. The ship's official status data were modeled to reflect standard operating conditions; some ships may have a negative history, while others may have a clean record. So, in the first step, information about each alternative A is collected. Table 2 shows the evaluation matrix for the set of alternatives A1-A13, assessed according to each criterion C1-C8. For example, vessel A3 made an alteration of course by 15 degrees relative to the previously maintained heading. The course change criterion is designated as C2, and the value is recorded in the data table. Additionally, documentation irregularities were retrieved from the vessel databases. Under criterion C8, the vessel is assigned a score of (1).