The ridge regression is presented for identify manoeuvring indices in Nomoto’s model, and the result indicates that the method is robust and does not rely on initial estimation. For selecting appropriate AIS data for manoeuvring indices predicting, a frequency domain identification method is presented.

This paper evaluates near ship-ship collision situations in the Tagus River Estuary using a simulation model of ship navigation in restricted waters. The simulation model consists of a ship collision avoidance model based on the Artificial Potential Field (APF) method, which has been improved to account for the lateral distribution of traffic along the route, the ship type and length and speed development of the ships along the trajectory. AIS data of ships entering and leaving the port of Lisbon are analysed to obtain the main characteristics of traffic parameters used as input for the traffic simulation model, such as: the routes of the vessels, speed distribution along the routes, traffic density and characteristics of the ships in each route, among others. First, the improved model of ship navigation and the Monte Carlo simulation technique are used to simulate the marine traffic in the Tagus River Estuary. Then, the concept of “ship domain” is used as collision criterion to determine the number of near collisions and the locations where they are most likely to occur. Finally, the simulation results are compared to the ones obtained from raw AIS data to assess the capability of the simulation model for marine traffic risk analysis.

Accidental damage to underwater cables caused by ship traffic seems to be a current problem. According to the statistics more than 44 percent of such damage is caused by fishing vessels. The reason for the next 14 percent is damage from ships’ anchors. The construction of the underwater installation risk model was based on the determination of the density of the traffic in the area where the installation is located. There are several models used to assess the risk of underwater cable damage requiring the implementation of data on the density of traffic of fishing vessels. For this purpose, they usually use AIS (Automatic Identification System) data or statistical data on traffic density in the areas called fishing squares. The aim of this article was to compare traffic data that was based on two independent systems AIS and VMS (Vessel Monitoring System) and verify the reliability of them. The research was carried out in the area of the Slupsk Bank where an underwater cable has been damaged several times. The authors have demonstrated the need to verify the data from both systems in order to obtain reliable information about fishing vessels.