The Probability of Close Overtaking in Fog

There is an increasing interest in crossing situations. This has been stimulated by the success of traffic separation schemes to generally reduce the level of risk of collision from ships approaching in opposing directions. There have recently been crossing collisions in the Dover Strait which have occurred during conditions of poor visibility. These might have been avoided if the officers in charge of the vessels had allowed more time to manoeuvre. They bear witness to the fact that, in fog, a vessel can travel a considerable distance before its course alteration is detected on another ship's radar and appropriate collision-avoidance action taken by that other vessel.

Section: Own Ship Bp {Initially 12khmentioning

confidence: 72%

Radar Simulator Studies of Crossing Encounters in Fog

Curtis¹

1986

“…Derivation of the expressions used to quantify the risk associated with drawing clear was based on the assumption that the manoeuvring phase is completed well before the passing and drawing clear phase takes place, and that consequently the course separation during the second phase is + D for overtaking and + D for meeting encounters. Following to some degree the ideas used by Curtis 3 and Cahill, 4 it was conjectured that a measurement of the risk associated with the passing phase could be derived from the time interval during which a 90 0 turn by either ship was likely to lead to a collision. It was found mathematically convenient to take the time during which the relative velocity vector effective after the turn passed within a distance L v equal to the mean length of ships measured from the central point of both vessels (Fig.…”

Section: The Methods Of W E I G H T I N Gmentioning

confidence: 99%

The Calculation of Marine Collision Risks

Lamb¹

1985

It has been recognized for some time that calculations of potential encounter rates based on the speed and lateral distributions of ships using sea routes provide only a partial estimation of the actual collision risk, as all encounters are usually given equal rating, and no attempt is made to include factors such as the degree of domain penetration or the relative speed of the ships. One possible solution to the problem consists in attempting to weight the calculated potential encounter rates according to the most relevant factors, and thus replace the calculated rates by weighted values to provide a relative estimate of collision risk. Goodwin, Lamb and Kemp reported a first attempt at such a procedure in their calculation of weighted encounter rates based on the observed traffic distributions and flow rates in the Sunk Lightship area in the neighbourhood of Harwich. A two-part index was used in the work; the first part employed a weighting factor based on the ratio of the time required for the completion of a manoeuvre involving a specified angle of course change, to the time available as measured from the ‘decision-distance’ at which the manoeuvre was deemed to commence. The second part used a factor based on the time required to pass and draw clear after completion of the manoeuvre.

“…This additional reaction time means that a considerable extra track separation must be allowed if there is still to be time to avoid collision should an unexpected manoeuvre occur'. 3 Aspect is of further importance in that it allows an immediate assessment of the difference in courses between the two vessels. Thus a vessel on a relative bearing of 40 0 can be determined, from the aspect alone to be, in one case, paralleling the own ship's course or in another, crossing and consequently a potential threat.…”

Section: The Development Of the M Arin E R -C O N T R O Lled Model Anmentioning

confidence: 99%

Towards Intelligent Ships in Marine Training Simulators

Colley¹,

Curtis²,

Stockel³

1986

Self Cite

An application of the model to manoeuvre ships based on the range to domain over range rate (RDRR) concept is described. A simulation of a training simulator has been set up on which the target ships manoeuvre by the RDRR model in response to mariner controlled ships. Results of experiments show that the RDRR model manoeuvres targets realistically. The applications are reduced instructor work load and increased simulator reality. The method has the potential for development to manoeuvre ships at sea.B. A. Colley is now with Plessey Marine, R. G. Curtis is with the Department of Trade and Industry and C. T. Stockel is at Plymouth Polytechnic.