## 5 Discussion  
Obtained results indicate that vessels entering the port are delayed more often than departing vessels and their delay lasts longer. Vessels calling at the ports of Szczecin and Police obtained a total delay of 104.8 h, while outbound vessels are responsible for 45.8 h of all delays. This means that as much as 70% of delays arise between the time a ship reports to the roadstead and its berthing time. In the context of ship type, bulk carriers and general cargo ships are delayed most frequently. As many as 44 of the 64 delayed ships (Table 8) were of this type (more than 73%). They account for 103.65 h of delay (Table 8) out of a total delay time of 150.62 h (69%). The result of the regression analysis showed that intensity only explains 44% of the variability in ship delays (Figure 5). An interesting discovery from our research was that the highest delays were not observed at high traffic intensities, but rather at moderate intensities (0.42-0.67 ships/h) (Figure 4). Using multiple regression analysis, it was shown that the situation is mainly caused by oversize ships subject to a one-way traffic rule throughout the entire passage (accounting for 88.5% of the variability) (Figure 5). Such a ship, which cannot pass any other vessel, can block the waterway for up to 5 h (average time for a ship to enter or leave the Basin Gorniczy quays). During this time, the waterway practically comes to a standstill, resulting in a drastic drop in intensity and a sharp increase in delays. This also explains the weak correlation between traffic intensity and the number of delayed ships (32% of the variability) (Figure 5). An oversize ship blocks the waterway, causing a decrease in intensity, while at the same time, more and more ships announcing their readiness to enter or leave experience delays. The hypothesis stating that delays are dependent on the intensity of traffic on the fairway is in 44% correct (according to the linear regression result). Delays increase drastically to 88.5% reliability (multivariate regression model) when a vessel with one direction of traffic appears on the fairway. With regard to financial losses, an optimistic conclusion can be made that, since intensity does not significantly affect vessel delays, these delays can be considerably minimized by modifying the regulations in the Port Regulations [36], thus achieving a decrease in delay time even at high traffic intensity. Based on the analysis of daily ship maintenance costs, it was concluded that the cost of maintaining a ship is closely related to its size. The waterway deepening project to a depth of 12.5 m is completed. This will result in the appearance of significantly larger vessels, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline No. & \begin{tabular}{c} **Intensity** \\ **(Ship/h)** \\ \end{tabular} & \begin{tabular}{c} **No of Ovesize** \\ **Vessels** \\ \end{tabular} & \begin{tabular}{c} **No of Vessels** \\ **with DG Cargo** \\ \end{tabular} & \
\begin{tabular}{c} **Model Delay (h)** \\ \end{tabular} &
\begin{tabular}{c} **Costs (USD)** \\ \end{tabular} \\ \hline
1 & 0.75 & 0 & 1 & 16.4 & 5251.3 \\
2 & 0.92 & 1 & 0 & 19 & 6109.2 \\
3 & 1 & 1 & 1 & 23.6 & 7584.9 \\
4 & 1.08 & 0 & 1 & 23.5 & 7543.5 \\
5 & 1.25 & 1 & 0 & 26.2 & 8401.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Predicted total delays for intensities that were not observed during the research. which also means significantly more expensive maintenance costs and, consequently, an increase in financial losses in the event of their delay. The conducted research has allowed for establishing the impact of the intensity of traffic on the delays of ships, which was found to be less significant than originally assumed. It has been shown that the correlations between ships resulting from the port regulations are much more important than their quantity on the waterway. It has also been determined which of the currently applicable Port Regulations [36] is responsible for the largest number of delays.