Study On The Simulation Model Of Pedestrian Flow Based On Cellular Automata

In developing countries,mixed traffic flow and pedestrian traffic flow play an important part in urban traffic flow in which walking acts as the most basic mode of trip for human beings.Whatever the vehicle adopted,walking cannot be spared at the trip origin and destination.In many metropolises of China,crowded pedestrian flow occurs in the pedestrian facilities such as pedestrian channel,overpass,public transport hubs and subway station in the traffic peak hour.Congested pedestrian traffic flow not only causes much inconvenience for pedestrian's trip but also results in an increase of trip delay time.Moreover,pedestrian stampede-crush accident might happen caused by severely assembled pedestrians in the mass campaign such as parade or assembly and audience in large stadium and cinema,etc.In recent years,national governments have been laying more and more emphasis on the study of pedestrian traffic flow and solutions to pedestrian traffic problem.However,pedestrian accidents caused by pedestrian traffic jam do occur now and then,which not only brings large amounts of economic loss to the society but also poses serious threat to people's lives.Therefore, the population explosion and the increasing traffic pressure in metropolises call for a great need to establish scientific theories of the pedestrian traffic flow based on the research on micro- and macro-characteristic of the pedestrian flow so as to guide pedestrian facility planning and pedestrian flow management and control to realize efficient and effective pedestrian flow guidance;avoid or alleviate pedestrian flow jam; and consequently maximize the utility of pedestrian facilities.In this dissertation,the simulation model of pedestrian flow is established based on the cell automata(CA) simulation theory by analyzing the micro-characteristics of pedestrian flow behavior. The study on emergent group behavior of pedestrian flow caused by the interaction of individual pedestrian micro-behaviors is carried out based on individual micro-behavior simulation,in which the formation mechanism of macro-characteristics of group behavior is explored and the relationship between micro- and macro-characteristics of pedestrian flow behavior is established.In the dissertation,laterally-interfered pedestrian flow,bi-direction pedestrian flow and pedestrian evacuation flow are simulated and analyzed based on CA.The main content of this dissertation is summarized as follows:(1) An overview of researches at home and abroad on micro and macro-characteristics of individual pedestrian and pedestrian group behavior are presented.It is then followed by an overview of studies on simulation of pedestrian flow at home and abroad from the perspectives of continuous and discrete simulation models based on the fact that computer simulation technology has become a major tool to study pedestrian flow.(2) The CA-based Dynamic Parameters Model(DPM) of pedestrian flow simulation is established.In the Dynamic Parameters Model,pedestrians can choose to wait or move to the eight neighboring cells as the next possible occupant position.In particular,the exchange of occupant positions is allowed in the pedestrian movement according to specific conditions.Meanwhile,four dynamic parameters: Direction-parameter,Empty-parameter,Forward-parameter,and Category-parameter are introduced to describe how individual pedestrians make their judgments on the conditions around.The concept of transition payoff is introduced to describe the relative advantages to be obtained by a certain pedestrian,through which the relationship between pedestrian as evaluator and available cells is established.It is assumed that the route choices made by pedestrians are driven by an intention to approach their destinations in a route as short as possible.Therefore,they are constantly weighing different possible choices of step.The transition payoff entailed to each cell for a pedestrian with a certain destination is represented and computed through these four dynamic parameters,which reflect the factors involved in the movement of pedestrians. While moving,pedestrians prefer the position with the largest transition payoff with an aim to acquire a movement benefit as large as possible.Therefore,the pedestrian would choose the cell with the largest value in the matrix of transition payoff as his or her target position.(3) Laterally-interfered pedestrian flow including four-way and perpendicular pedestrian flow is simulated and discussed by using Dynamic Parameters Model.The velocity-density and volume-density relationships will be studied and analyzed with different system sizes and parameter weights.The effect of system size and parameter weight on the simulation curve and critical density is analyzed.Comparisons between Dynamic Parameters Model and published pedestrian simulation models are carried out from pedestrian movement rules and simulation results.(4) Bi-direction pedestrian flow is simulated and discussed by using Dynamic Parameters Model from the perspectives of direction split,system size and walking habit respectively.The relationships of velocity-density and volume-density will be studied and analyzed.The effect of direction split,system size and walking habit on simulation curve and critical density is also analyzed.The evolution process of bi-direction pedestrian flow is simulated with different initialization conditions.The Right-hand-parameter is introduced and defined in great detail in this part to describe and reflect pedestrian's walking habit of keeping to the right in their movement.(5) Pedestrian evacuation flow is simulated and discussed by using Dynamic Parameters Model with three possible circumstances taken into consideration,involving the evacuation conditions under which there is no visible adverse effect,or there exists obstacles or pedestrian's visual field is affected.The effect of exit number,pedestrian density and exits layout on evacuation time in the evacuation room without adverse effect is discussed.In the simulation with evacuation obstacle,the method of computing the value of static floor field with obstacles is presented based on Euclidean distance, through which the direction-parameter is computed and the pedestrian evacuation from rooms with different layouts of obstacles are simulated.In the simulation with pedestrian's visual field affected,the pedestrian evacuation characteristics are discussed considering the cases in which pedestrians blindly move without evacuation sign or pedestrians move along the wall with evacuation sign available.The evacuation room is divided into exit visible area,wall visible area and wall invisible area by pedestrian sight radius.Different methods of computing direction-parameter in these areas are presented to describe pedestrians' varied movement characteristics under these circumstances.The effect of pedestrian sight radius on evacuation time and the number of remaining pedestrians is also discussed.