Research On Ship Traffic Flow In Waterway Based On Cellular Automaton

With the development of maritime transportation,ships are becoming larger and faster.In some important waterways,the density of ships is becoming higher and higher.In such congested waterways,more actions,like following,overtaking,etc.,are observed than before,which make the ship traffic complicated.It is necessary to build traffic models for the microcosmic behaviors of ships following and overtaking to reveal the generating mechanism of the complicated traffic phenomena,which can promote the development of maritime traffic flow research.The traffic flow model based on cellular automaton(CA)is a kind of microcosmic model for traffic flow,which is widely used in vehicles and ships traffic flow research.It is one of the main traffic flow models now.By studying the CA models and its applications in maritime traffic flow,the bottleneck problems that prevent the development of ship traffic flow based on CA have been analyzed and summarized.To solve the problems,by analyzing the ships' traffic data in waterways and studying the movement characteristics of ships,some new methods were proposed and the model for ship traffic flow in sea waterway was built.A spatial discretization method for waterway was proposed based on spatial-logical mapping(SLM)rule.The purpose of this method is to solve the spatial discretization problems caused by the changes in waterway width.Based on traditional methods for road traffic,lanes may be reduced or added after spatial discretization when the width of a waterway is variety,which would cause the ship "pseudo lane-change phenomenon".This problem seriously hinders the application of cellular automata in the study of ship traffic flow.Therefore,by analyzing the characteristics of ships' trajectories distribution and sailing behaviors in waterways,the new method for the spatial discretization of waterway was proposed.By this method,the spatial discretization results of waterway with width variation can be mapped to a new waterway with width invariableness.Based on this spatial discretization results,the update rules in CA model can be built reasonably.By this method,the narrowed waterw was discretized.Based on the discreted results,the ship traffic flow in the waterway was simulated.By comparing the simulation results and measured data,the effectiveness of the method was tested.A CA-based traffic model for ship traffic flow in one-way waterway was proposed when the overtaking action was limited.In this model,the deceleration action of a ship,which was impacted by the preceding ship,was studied when the lag ship can not overtake the preceding ship.To decide the time and amplitude of acceleration and deceleration,which was used to build the update rules in the CA-based model,the research of collision avoidance was considered.Then updata rules were made and the model was built.This model can be used to simulate the ship traffic flow when there is just one lane or the overtaking is not allowed.And it is the fundamental model for ship traffic model when the overtaking action is allowed.A CA-based traffic model for ship traffic flow in one-way waterway was proposed when the overtaking action was allowed.In this model the ship overtaking action was studied and the updata rules were built.In the update rules,another close-quarter situation should not be resulted by the overtaking action,ship-to-ship communication in collision avoidance,a ship's velocity change during its overtaking,scheduling conflicts in lane changing,etc.were considered,which made the rules very accordance with the characteristics of actual ship traffic.To test the performance of the model,the simulation of ship traffic flows in waterways were carried out.By the studying above,the problem of "pseudo lane-change" caused by the width change of waterway was solved.The CA-based models for ship ship traffic flow in one-way waterway were proposed for ships' following and overtaking actions.The researches promote the application of CA in marine traffic model,and make a contribution to the development of marine traffic flow theory.