## 3 Materials and Methods  
Figure 3 presents a visual representation of the research process, highlighting the main steps involved in analysing ship delays and financial losses on the Swinoujscie-Szczecin waterway. The subjects of the study are vessels participating in traffic on the Swinoujscie-Szczecin waterway calling at the ports of Szczecin and Police. Ships using the port of Swinoujscie are subjected to observation only in the situation of direct correlation with ships entering or leaving ports of Szczecin and Police, i.e., having a direct impact on their delay. The study does not include inland traffic and port service (e.g., barges, tugboats). The ongoing project \"Modernization of the Swinoujscie-Szczecin waterway to a depth of 12.5 m\" and any delays resulting from it are not the subject of this research. The study focuses on delays resulting directly from the Port Regulations [36; 37]. During the research, the following dependencies and limitations were identified:  
1. Ships to be provided with one direction of traffic (ODT) on designated sections of the waterway or on the entire route of their passage. 2. Ships that cannot pass each other due to exceeding total length. 3. Ships that cannot pass each other due to exceeding total width. 4. Vessels that cannot pass each other due to exceeding the limit of drafts. 5. Ships which cannot enter or leave the port due to the prevailing hydro-meteorological conditions. Ships with the obligation to maintain one direction of traffic are most commonly oversize vessels, and their case has been studied more extensively in [38]. Those vessels participate in traffic on the studied waterway under special conditions, which will be presented in more detail in the following part of the article. In this work, a separate category of delays generated by Ro-Pax ferries entering the port of Swinoujscie was identified and examined. The exceeding of the technical parameters between ferries and ships from the ports of Szczecin and Police (i.e., total length or/and width or permissible drafts) was treated as an identical cause of delays, referred to as \"ferries\" in the work. The research lasted from 1 April to 30 June 2021 and was collected during 12-h shifts taking place between the hours of 8:00 AM and 8:00 PM and 8:00 PM and 8:00 AM. In total, 56 observations were conducted. If, during observation, the ship experienced a delay due to Port Regulations [36], the time of the delay, its duration, and its cause were recorded. It should be noted that the system does not provide an automatic recording of ship delays in the VTS database. All delay measurements and analyses of their causes were observed and recorded in real-time during the service, with a detailed knowledge of the Port Regulations [36] and with the use of database tools. The database provided information on the actual time of passing the breakwater heads in Swinoujscie by the  
Figure 3: Flowchart of conducted analysis. vessels being studied. Time stamps of passing the breakwater were used to calculate the intensity on the waterway during one observation. The time of passing the breakwater heads in Swinoujscie was also used to calculate the delays of ships entering the ports of Szczecin and Police by comparing the planned time of passing the breakwater heads, based on Estimated Time of Arrival (ETA), with the actual time of passing them. The calculated intensity for each of the 56 observations was analysed to determine the correlation between traffic intensity on the waterway and the resulting delays. In order to understand this correlation, a univariate and multivariate regression analysis was carried out. The next stage of the research was to isolate the most frequent cause of ship delays resulting directly from the Port Regulations [36]. All the causes of delay that occurred during the research were analysed and seven main regulations were identified as causing ship delays on the studied waterway. The results of this part of the research were presented in the further part of the article.