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New collision prevention system for ships

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A new warning and information system to help prevent collisions between ships has been developed by the “Maritime Policy” research group of the University of Cadiz. The researchers primarily responsible are Juan Carlos Rasero and Nieves Endrina, and the system is known by the acronym SAAB (from the Spanish 'Sistema de Ayuda Anticolisión para Buques'). The invention consists of a system designed to support the Duty Watch Officer of the vessel in taking timely and correct decisions on the manoeuvres necessary when there is an imminent risk of collision with one or more other vessels. This simple and clear system will be a powerful new tool for decision-taking by the Watch Officer, when collision avoidance action must be taken very rapidly in extreme situations.

The system comprises a series of modules in each ship involved.

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Currently substantial efforts are being made in the maritime navigation sector to stop or reduce collisions between ships. Such collisions are significant causes of the loss of human life, losses of vessels and their cargos, and damage to the natural environment of the sea and coastlines. These efforts are being directed towards various different aspects of the problem, in particular the human factor, maritime regulation, the technical evolution of ships and, most importantly, marine navigation equipment.

The invention reported here is based on a basic reasoning. Apart from 'force majeure', if vessels make the correct manoeuvres at the correct time, the collision will not take place. On the contrary, if the Situation Reaction Limit (SRL) is passed, the collision will happen.

It can be concluded from this simple reasoning that, to avoid the collision, it is necessary to know the SLR, which is defined as that moment in time when, because of the distances between the vessels, the ruling environmental conditions, and capacity of the vessels to change course and speed, the collision cannot possibly be avoided.

The invention proposes a system that first alerts and reports to the Officer of the Watch that the vessel is approaching the SRL and, second, proposes the manoeuvre that must be made in order to avoid the collision.

For this, the system will display simultaneously on the corresponding screens on board the vessel, two types of graphic information:

  • 1. Future trajectories, with display of the horizontal silhouettes of the system's own vessel and other vessels in potential conflict, for a specific interval of time.
  • 2. Curves of evolution, of least advance and change of course – rudder hard to left or right - for the speed, heading and meteorological conditions at that moment, to both port and starboard for the vessel itself and for the other vessels involved.

With this information available to the Officer of the Watch,

  • 1. From the graphic representation of the future trajectories, the Officer will know the position and time of impact of the impending collision in the event of it occurring.
  • 2. From the curves of evolution, shown for both port and starboard directions for the vessel itself and the vessels in conflict:
    • a. If none of the curves crosses with that of another vessel, the Officer will know that it is possible to make the manoeuvre to port or to starboard.
    • b. If only two curves of evolution cross, the Officer will know that the other two do not cross, i.e. on those headings a collision is less likely. Therefore, the Officer of each vessel will know which way to steer, to port or starboard, to avoid each other (see fig.).
    • c. If the four curves cross the Officer will know the collision is predicted to happen whether the vessel is steered to port or starboard. In this case the system will tell the Officer what is the correct manoeuvre to take according to the International Regulations for Preventing Collisions at Sea (COLREGs).

There is a further safeguard, not covered by the above. If, for any reason, one or other of the vessels involved does not make the correct manoeuvre, the system would indicate, by visual and audible alarms, if the two curves of evolution are going to intersect at the same moment in time, that is, if a collision is going to occur.

With this information the Officer of the Watch has a powerful, simple and clear tool for deciding what action to take to avoid the collision. Another notable aspect of this invention is that it is based on equipment already existing on board vessels. Therefore it can be implemented at relatively low cost and with the minimum transformation of the existing equipment.

The system comprises a series of modules in each ship involved: a calculator of future positions; a calculator of curves of evolution; a database of curves of evolution; a generator of ship silhouettes; and a modified Automatic Information System (AIS). It would also include a module for the transformation of the information received in respect of the other vessels, so as to present this information on screen. The functioning of these modules depends on algorithms, data bases and measurements provided by various sensors.


  • The system is based on making certain modifications to the currently existing equipment. New hardware is not required.
  • It is inexpensive and easy to implement.
  • It provides valuable information in real time between vessels.
  • It provides effective support for the Officer of the Watch for rapid and informed decision-making in critical situations.
  • The system can be applied in all those vessels that, under international regulations, should have an AIS system installed.


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