Study On Marine Traffic Flow Complexity Metric

With the growth of the Chinese economic, ports are becoming the busiest waterarea in the world. Especially, the recent increase in the number of high-speed,large-scale, and heavy-load ships has seen marine traffic flow become increasinglymore complex. The larger number of ships occupying the same water area andtravelling at faster speed has resulted in crowding and faster evolving trafficsituations and exacerbated the pressure of marine traffic safety. An accurateunderstanding of this marine traffic is a precondition for effective management andcontrol of waterways.Marine traffic flow theory is the fundamental theory for understanding andmanaging the traffic flow. With the change of the traffic situation, the characteristicsof nonlinear and complex have become more and more obvious. But the currentmarine traffic theory hasn’t taken these characters into account. On the contrary, thetraffic complexity researches in other traffic fields have become the hot issue, such as:air and road transportation area. Therefore, re-recognizing the traffic flow in thecomplex science way is necessary and basic for the marine traffic complexity study.In this thesis, the marine traffic flow system was extracted from marine trafficsystem as an object of the study. The Complex theories have been proposed toanalyze the complexity characteristics in marine traffic flow system. The macroscopicmarine traffic complexity model (in the view of traffic managers) and microscopicmarine traffic complexity model (in the view of own ship) were constructed based onthe definitions of marine traffic cognitive complexity and content complexity. Themain research contents of the thesis are listed as following:Firstly, the complex phenomenon in marine traffic flow was detected to verify thecomplexity characteristics in marine traffic flow system. The result showed thattraffic flow system is a complex system and it possesses both the cognitivecomplexity and content complexity. Therefore, the thesis defined the trafficcomplexity in two dimensions: cognitive complexity and content complexity.Compared with the concepts of ship collision risk (SCR), the marine traffic contentcomplexity contained the SCR. Not only the cognitive complexity, but also the content complexity was supposed to describe the traffic situation which is related tosupport the nautical safety.Secondly, according to the definition of cognitive complexity, the thesis built amacroscopic complexity model for traffic manager and put forward the process ofcounting the macroscopic complexity:(1) catalog the similar ships (in similar motionand near distance)into a traffic cluster;(2) establish the historical traffic flow field;(3)evaluate the aggregation complexity in the cluster;(4) count the speed-diachroniccomplexity of the cluster;(5)calculate the density-diachronic complexity of thecluster;(6) show the cognitive complexity in the macroscopic complexity map. Thesimulation experiment show the macroscopic complexity model is available fordemonstrating the distribution of complexity in space.Finally, based on the definition of content complexity, A microscopic complexitymodel was developed to evaluate the content complexity around the own ship.According to the encounter process of two ships, the conflict-complexity model andthe collision-complexity model are employed to evaluate the traffic situation indifferent phases.(1) The conflict-complexity model is used to assess the trafficsituation, when relative distance is more than1NM. The model is made up ofrelative-distance, DCPA (Distance at Closest Point of Approach) and TCPA (Time toclosest point of approach). Multi-group experiments have been designed toinvestigate the effectiveness of the conflict-complexity model. As a consequence, theconflict-complexity model can show the traffic situation around own ship, and it canbe used to find the solution of collision avoidance for own ship as well.(2) When thedistance is less than1NM, collision-complexity model will play the major role. Incollision-complexity model, the ship maneuverability and avoid collision actionswere taken into account to construct ship hazard zone (SHZ), the complexity can becalculated by the proportion of overlap SHZ.