Port tugs are an important element in port activity and navigational safety issues. Port tugs ensure the safety of big ships while they are entering, manoeuvring, mooring and unmooring, and are of huge importance during other port operations. At the same time, optimizing the number of port tugs and tug bollard pull is also important from a port navigational safety and economic point of view. Calculation and evaluation methods of the optimal request for tugs bollard pull, in particular, port operations, are very important in order to guarantee the navigational safety of the port and ships during the main ship operations in the port. This article provides the number of requested port tugs and bollard pull calculation and evaluation methods on the basis of forces and moments acting on ships. On the basis of real ship voyages and manoeuvring at ports data as well as high accuracy simulators, theoretical methods were used, which were followed by our conclusions and recommendations, which can be used by port harbour masters and tug companies. Modern tugs have become an important element and integral part of modern port navigational safety. Such modern port tugs are also used for navigational safety and other important port functions and activities, such as fire protection and search and rescue operations. The optimal number and capacity evaluation of port tugs depending on port capacity and conditions are studied in this article.

Optimization transportation cargo and passengers between ports and regions are very important, because industrial regions are located some distance from ports. The demand for energy request for the movement of transport is a necessity in the modern world. Transport and activity called transportation are used daily, everywhere, and a lot of energy is needed to power the various transport modes. Today different transport modes are being used to transport passengers and cargo. It is quite common to use road transport, which can transport passengers and cargo from door to door. Considering alternative possibilities (road, railway and/or inland waterway transport), it is important, based on theoretical and experimentation, to identify optimal solutions. In finding transport modes that are either most technically or economically effective, we could unearth possible solutions which would require minimal energy use. Unfortunately, with increased transportation, this often leads to traffic congestion on the roads, which requires additional energy (fuel). This situation generates requirements from many stakeholders in terms of finding ways to decrease the transportation time and energy (fuel) consumed by transport modes. A theoretical method evaluation is conducted on the optimal transportation possibility that minimizes transportation time and energy (fuel) use by employing graph theory, which is presented in this paper. The scientific contribution is the development of a transport modes comparative index, which is then used for evaluations. This paper presents possible alternative transportation conditions based on a multi-criteria evaluation system, proposes a theoretical basis for the optimal solutions from an eco-economic perspective that considers energy, and provides for experimental testing during a specific case study. The final results from the case study provide recommendations and conclusions.

In many ports, the ship's speed is limited for the safety of navigation. At the same time, ship captains and port pilots choose the speed of the ship, but not higher than the permitted speed of the ship in the port, therefore the speed of the ship also depends on the experience of the ship captains and port pilots and the sailing conditions of the ship in specific conditions. Choosing the optimal speed of ships in port, including the effect of shallow depth, can reduce fuel consumption and ship emissions in ports, which is important for the development of green and sustainable ports. In all cases, shipping safety is the highest priority. The main objectives of the article are determining the optimal speed of ships in ports with low clearance, ensuring navigational safety, reducing fuel consumption and emissions, and at the same time creating a sustainable port. The article presents the methodology of optimal ship speed calculation, minimum ship controllable speed maintenance, fuel consumption and emission reduction methodology and their impact on sustainable and green maritime transport and port development. The developed methodology was tested on real ships and with the help of a calibrated simulator, sailing through harbor channels and harbor waters in low clearance conditions.

In a majority of ports, a ship’s speed is limited for reasons of navigational safety. At the same time, captains and port pilots choose the speed of the ship, but it cannot be higher than the speed allowed in the port. Therefore, the speed of the ship also depends on the experience of the masters and harbor pilots and the sailing conditions in specific situations. Choosing the optimal speed of the ship in the port, considering the hydrodynamic effect of shallow water and the controllability of the ship, can help reduce fuel consumption and ship emissions, which is important for the development of a sustainable port. In all cases, the safety of the shipping is the highest priority. The main objectives of this article are determining the optimal speed of ships in ports with low clearance under a ship’s hull, ensuring navigational safety, reducing fuel consumption and emissions, and creating a sustainable port. This article presents the methodology for calculating the optimal ship speed as the minimum controllable speed, fuel consumption and emission reduction, as well as its implications for sustainable and green maritime transport and port development. The methodology presented has been tested on real ships and using a calibrated simulator, navigating through port channels and port water’s restricted conditions.

Harbour tugs are usually used to moor ships if large ships do not have their own additional propulsion devices (thrusters). Alternatively, during ship loading operations, ships sometimes have to be transferred from one quay to another, and in some cases, port users (shipping companies or other companies) have to pay for port tug services. In such cases, it is very important to guarantee the safety of shipping during mooring operations and to use tugboats optimally and at the same time reduce the cost of tugboat services for ship operators and other companies. For the optimal use of tugboats, it is very important to accurately estimate the required traction force (bollard pull) of tugboats and their quantity, taking into account the parameters of moored ships, the locations of berths, hydro-meteorological and hydrological conditions, and clearance (the gap between the ship’s hull and the bottom of the water area), in order to guarantee the safety of navigation and not to order an excess of tugboats in terms of their quantity and powers. This article presents a methodology developed for estimating the required bollard pull and the number of tugs, taking into account the parameters of the ship, hydro-meteorological and hydrological conditions, clearance, and the locations of berths. The developed methodology for estimating the number of tugboats and their traction force (bollard pull) was tested in real conditions (with real ships and tugboats) and using a calibrated simulator, and we found that it can be successfully applied in any port or other complex shipping area by adapting it to specific conditions. The developed methodology for calculating the traction power (bollard pull) of tugboats allows us to determine the required traction force of tugboats in advance with sufficient accuracy, achieved by assessing the specific parameters and environmental conditions of the vessel served by tugboats. In the most difficult areas of the port, in terms of the use of tugboats, this methodology allows us to make reasonable decisions regarding the number of tugboats and the traction force (bollard pull) required and at the same time reduces the risk of emergency situations.