Research On Ship Traffic Flow Simulation In Lao Tieshan Channel Based On Cellular Automaton

With the development of one belt one road initiative proposed by President Xi Jinping,the international maritime transportation also obtained a new opportunity of development.The flow and density of ships in some important domestic and international waterways are increasing constantly coupled with the expansion of microscopic behavior of ships,leading to the rising of following and overtaking activities of ships in these important channels from the micro level.In order to solve and study the mechanism behind these complex traffic phenomena,it is full of necessity to model the ship traffic flow from the perspective of complexity science and traffic engineering to study various micro behaviors.As a microscopic method of traffic flow simulation,Cellular Automaton(CA)is widely used in the study of road and marine traffic flow.However,compared with road traffic model,the research on marine traffic flow is mainly based on the fundamental diagram theory,while the relatively new three-phase traffic model is rarely referred to.Although the dispute between the two theories is,so far,still not unified,there is a consensus that both theories have their rationalities.Inspired by the road traffic engineering method,this dissertation adopts the technique of seeking common ground while reserving differences.Starting from the measured data,by combining the reasonable parts of the two theories,the new models of following and overtaking are established to deepen the understanding of marine traffic flow.By summarizing the development of ship traffic flow model,the shortcomings of the research in current simulation circumstances are found.By analyzing the Automatic Identification System(AIS)data of ships in the channel,the characteristics of ship behaviors are acquired.Combined with the research achievements of marine traffic engineering,a ship traffic flow model based on CA is established.The feasibility of the experimental method is proved by the comparison of AIS data and related mathematical methods.Firstly,the model is established under the condition of following in one-way channel,mainly analyzing the behavior of deceleration affected by the front ship when the speed of the rear ship is higher than that of the front but not allowing overtaking.In this dissertation,the speed adaptation mechanism of three-phase traffic flow theory is introduced to reflect the probability of slowing down,so the speed of the rear ship will change with the action of the space distance and the speed of the front ship.By combining the safe distance between ships and the rules for collision avoidance,the time and amplitude of deceleration are determined and an improved Nagel-Schreckenberg(NS)model is obtained by referring to the corresponding update rules.From the comparison of simulation results and actual measurement,the introduction of speed adaptation mechanism makes the new model reflect the real traffic circumstances to a certain extent.This model is applied to the simulation of ship traffic flow when overtaking conditions are not satisfied,which lays a foundation for the establishment of simulation under the condition of overtaking in one-way channel.After that,the ship traffic flow model of following is extended to the two-lane condition,so the new model under overtaking condition is established.The behavior of lane changing of ships is mainly studied in this model and the update rules are formulated based on the International Regulations for Preventing Collisions.It has been taken into consideration that a new urgent situation should not be arisen between ships in the process of overtaking as well as the influence of speed affected by the rear ship which takes a turn to overtake to ensure the safe lateral distance and the target position conflict which may occur when two or more ships take the action of overtaking in order to make the simulation more in line with characteristics of the actual situation,meanwhile,the causes of speed adaptation mechanism are explained.Through the comparison with the measured data and the verification of related mathematical methods,it concludes that the simulation used in this dissertation belongs to a transition model between the above two theories.By improving the model under the framework of fundamental diagram theory,the similar synchronous flow can be simulated and named as quasi synchronous flow.The simulation method can promote the application of three-phase traffic theory in ship traffic flow modeling,and provide a new thinking for the development of ship simulation.