Extended Cellular Automaton Model Research Articles

Effect of Different Time Step Sizes on Pedestrian Evacuation Time under Emergencies Such as Fires Using an Extended Cellular Automata Model

The cellular automata (CA) model has been a meaningful way to study pedestrian evacuation during emergencies, such as fires, for many years. Although the time step used in the CA model is one of the most essential elements, there is a lack of research on its impact on evacuation time. In this paper, we set different time step sizes in an extended cellular automaton model and discuss the effect of time step size on the overall evacuation time under different emergency types and levels. For a fixed step time mode, the larger the time step, the longer the evacuation time. In each time step size, the evacuation time gradually increases with the increase of emergency level, and there is a sharp increase when the time for pedestrians to move one step is exactly an integer multiple of the time step. When there is no friction between pedestrians, the evacuation time at each time step first decreases slightly with the increase of emergency level and then remains unchanged; the larger the time step, when the evacuation time remains unchanged, the lower the emergency level and the greater the evacuation time. For the variable time step model, when the friction between pedestrians approaches infinity, the total evacuation time does not change with the emergency level; when the friction between pedestrians is reduced, the total evacuation time slightly decreases with the increase of the emergency level. The less friction there is, the more significant the reduction. The results of previous actual experiments are also reflected in the simulation at a lower emergency level. The result shows that the time step size significantly impacts the evacuation simulation results of the CA model, and researchers should choose carefully to obtain more realistic simulation results.

Effects of exit obstacles on the evacuation dynamics of blind people

The modeling of blind people’s behavior is an important topic in pedestrian evacuation dynamics. In order to study movement characteristics of blind people in evacuation process and the effect of indoor obstacles on the evacuation efficiency of blind people, an extended cellular automata model is proposed to simulate blind people evacuation by considering the influence of obstacles. The control variable method is adopted to study the effect of indoor obstacles on the blind evacuation efficiency rule. The numerical simulation is applied to analyze the evacuation process of blind people under different setting (e.g. the location, size and other factors) of obstacles and different evacuation scenarios. The shunt effect of obstacles is discussed and the layout strategy of obstacles is optimized. The results show that the longitudinal obstacles in front of the exit can effectively play the diversion role of obstacles when the obstacle is at a certain distance from the exit, which will improve the evacuation efficiency of the blind. Furthermore, a horizontal obstacle of appropriate length can constrain the trajectory of the blind people and improve the efficiency of evacuation, but when the horizontal obstacle is too long, it will induce extra jam on both sides of the obstacle and hinder the evacuation of the blind. The finding can provide the theoretical basis for the blind people’s organization, management and the optimization of evacuation strategies during an emergency.

Simulation Study of Pedestrians Evacuation Considering Aggressive Behavior

Conflict during an evacuation may turn into aggressive behavior and create problems for evacuation. To study the influence of attack behaviors such as pushing and shoving on evacuation and the evacuation law, an extended cellular automata model is developed in this paper. In the model, pedestrian movement is influenced by static, dynamic, and attack floor fields. In addition, pedestrian vision is influenced by the direction and location of movement of surrounding pedestrians, and pedestrians adopt different coping strategies for attacks: avoidance detour, or imitation. Attacker movement and aggressive behavior are also studied. Numerical simulations are conducted to discuss the pedestrian evacuation problem under attack behavior. The effects of the evacuation process, attack field sensitivity coefficient, location of fallen pedestrians, pedestrian density, number of initial attackers, initial attacker location, and pedestrian imitation ratio on evacuation time and number of fallen pedestrians are analyzed. The simulation results show that an appropriate increase in the impact of the attack field can slow down the congestion, that is, the evacuation time is the fastest at kA = 0.5. The evacuation time is faster when the room is full of normal pedestrians or full of attacking pedestrians. The number of casualty pairs is high when the initial position of the attacker is in the middle of the inner side of the room. The results of the study can provide recommendations and guidance for the formulation of evacuation strategies for pushing and shoving type attacks and reducing casualties.

Effects of aggressiveness on pedestrian room evacuation using extended cellular automata model

Effects of aggressiveness on pedestrian room evacuation using extended cellular automata model

Impact of vehicle platoon on energy and emission in mixed traffic environment

Vehicle platoons were recently proposed to reduce energy consumption and emissions. However, the majority of platooning studies have focused on pure connected automated vehicle (CAV) environments with limited insights into energy consumption and emissions. This paper quantifies fuel consumption and emissions by studying the microscopic movements of CAVs and human driving vehicles (HDVs) in mixed traffic flows. With an extended cellular automaton model, a four-lane mixed traffic flow of CAVs and HDVs is investigated in detail. The results have shown that ad hoc platoon formation can lead to frequent acceleration and lane changing, resulting in more fuel consumption and emission. With a dedicated CAV lane (DCL) strategy, the interference of CAVs and HDVs is greatly reduced, thereby improving the fuel economy and emission reduction. The findings can benefit the organization of vehicle platoons in the persisting mixed traffic flow environment.

Model considering panic emotion and personality traits for crowd evacuation

Panic is a common emotion when pedestrians are in danger during the actual evacuation, which can affect pedestrians a lot and may lead to fatalities as people are crushed or trampled. However, the systematic studies and quantitative analysis of evacuation panic, such as panic behaviors, panic evolution, and the stress responses of pedestrians with different personality traits to panic emotion are still rare. Here, combined with the theories of OCEAN (openness, conscientiousness, extroversion, agreeableness, neuroticism) model and SIS (susceptible, infected, susceptible) model, an extended cellular automata model is established by the floor field method in order to investigate the dynamics of panic emotion in the crowd and dynamics of pedestrians affected by emotion. In the model, pedestrians are divided into stable pedestrians and sensitive pedestrians according to their different personality traits in response to emotion, and their emotional state can be normal or panic. Besides, emotion contagion, emotion decay, and the influence of emotion on pedestrian movement decision-making are also considered. The simulation results show that evacuation efficiency will be reduced, for panic pedestrians may act maladaptive behaviors, thereby making the crowd more chaotic. The results further suggest that improving pedestrian psychological ability and raising the standard of management can effectively increase evacuation efficiency. And it is necessary to reduce the panic level of group as soon as possible at the beginning of evacuation. We hope this research could provide a new method to analyze crowd evacuation in panic situations.

Microscopic traffic behavior modeling and safety evaluation in mixed traffic area of bus station

With the development of Chinese cities, the mixed behavior at bus stops during the early commuting period is severe, which seriously affects the safety of passengers. Thus, in this paper, we propose a cellular automaton (CA) model to simulate bus arrival, non-motor vehicles movement and passenger boarding processes in mixed traffic area of bus station. Data is collected to explore the passengers’ movements and the complex traffic phenomena (e.g., bus's two driving routes and different number of arriving buses simultaneously) at the station. Based on collected data, the parameters are calibrated and the simulation scenario is built. Numerous simulations are conducted to further analyze the impact of microscopic behaviors of buses and passengers on safety at bus station. Moreover, the most dangerous areas of bus station are delineated under the extended CA model. Comparison between two cases with and without non-motor vehicles reveals that the non-motor vehicles have prominent negative impacts on safety. Finally, some suggestions for bus drivers, passengers and managers are proposed from the perspective of safety. The above results provide a theoretical foundation for the effective management of passengers and bus drivers at bus station.

An extended model describing pedestrian evacuation considering pedestrian crowding and stampede behavior

In recent years, stampede accidents have occurred frequently, resulting in significant casualties and property losses. In this paper, an extended cellular automata model is designed to investigate the behavior of pedestrian stampedes. The concept of pedestrian crowding, support, and friction is introduced and viewed as an influencing factor of normal pedestrian falls Besides, the state of pedestrians after falling to the ground is analyzed. The fallen pedestrians may return to normal or be trampled to death. Through the numerical simulation, the stampede phenomenon in pedestrian evacuation in public places is explored, and the influences of pedestrian density, pedestrian distribution mode, exit setting, and obstacles at the exit on the evacuation results are discussed. The analysis demonstrates that the greater the pedestrian density, the more the pedestrians fall to the ground and die. Moreover, pedestrians are more likely to die after falling to the ground with the increase in pedestrian density. At the beginning of the evacuation, the risk of the pedestrian stampede in decentralized distribution is less than that in centralized distribution. The exit is located on the left or right of the center of the wall when the pedestrian density is small, making it less dangerous than the middle position. The safety is higher when the number of exits is large. Additionally, the existence of obstacles at the exit can reduce the risk of stampede accidents when the pedestrian density is small. Our research reveals the mechanism and influencing factors of the trampling process to a certain extent, playing a reference and guiding role for future research.

Simulation of a pediatric hospital in evacuation considering groups

Pedestrians will form groups in both normal and emergency sometimes. Members of these groups usually have certain social relations. We study emergency evacuation of pedestrians in a pediatric hospital in this paper. Pedestrians there have their own particularities. First of all, all patients are children. Secondly, the patients usually have no ability to see a doctor alone. They are always accompanied by their families. Thirdly, children of different ages move at different speeds, which is heterogeneous. Fourthly, pedestrians usually move in family units. Family units and independent pedestrians are also heterogeneous. According to our actual observations, pedestrians are mostly composed of three-person groups, two-person groups and independent ones. Each group usually has one leader and the rest are followers. We use an extended cellular automata model considering groups to study such evacuation. The rule of both overlapping and speeding up are set in the model to realize the change from heterogeneous to homogeneous from the view of speed. The local density field and its range R are introduced. The field can lead pedestrians move to the area with low density. The range R=4 is optimal because of the family relation. The priority order is added to avoid conflicts. Groups with child have priority over independent pedestrians. The cohesive distance between leader and follower ensures members of the group always stay together, but the shape of the group is changeable in simulations. The evacuation time, waiting time and path of each pedestrian are analyzed. The simulation verifies the phenomenon that pedestrians behind tend to follow the front. The rules together release more free space to drastically reduce evacuation time and waiting time of groups, but independent pedestrians are not influenced greatly.

An extended cellular automata model with modified floor field for evacuation**Project supported by the Sichuan Youth Science and Technology Innovation Research Team Project, China (Grant No. 2019JDTD0017), the National Natural Science Foundation of China (Grant No. 41702340), and the National Science and Technology Major Project of China (Grant No. 2017ZX05013001-002).

The floor field model has been widely used in evacuation simulation research based on cellular automata model. However, conventional methods of setting floor field will lead to highly insufficient utilization of the exit area when people gather on one side of the exit. In this study, an extended cellular automata model with modified floor field is proposed to solve this problem. Additionally, a congestion judgment mechanism is integrated in our model, whereby people can synthetically judge the degree of congestion and distance in front of them to determine whether they need to change another exit to evacuate or not. We contrasted the simulation results of the conventional floor field model, the extended model proposed in this paper, and Pathfinder software in a same scenario. It is demonstrated that this extended model can ameliorate the problem of insufficient utilization of the exit area and the trajectory of pedestrian movement and the crowd shape of pedestrians in front of exit in this new model are more realistic than those of the other two models. The findings have implications for modeling pedestrian evacuation.

Simulation-based optimization of inner layout of a theater considering the effect of pedestrians**Project supported by the National Natural Science Foundation of China (Grant Nos. 11572184 and 11562020), the National Basic Research Program of China (Grant No. 2012CB725404), and the Research Foundation of Shanghai Institute of Technology (Grant No. 39120K196008- A06).

We propose an extended cellular automaton model based on the floor field. The floor field can be changed accordingly in the presence of pedestrians. Furthermore, the effects of pedestrians with different speeds are distinguished, i.e., still pedestrians result in more increment of the floor field than moving ones. The improved floor field reflects impact of pedestrians as movable obstacles on evacuation process. The presented model was calibrated by comparing with previous studies. It is shown that this model provides a better description of crowd evacuation both qualitatively and quantitatively. Then we investigated crowd evacuation from a middle-size theater. Four possible designs of aisles in the theater are studied and one of them is the actual design in reality. Numerical simulation shows that the actual design of the theater is reasonable. Then we optimize the position of the side exit in order to reduce the evacuation time. It is shown that the utilization of the two exits at bottom is less than that of the side exits. When the position of the side exit is shifted upwards by about 1.6 m, it is found that the evacuation time reaches its minimum.

Effect of dangerous source on evacuation dynamics in pedestrian counter flow

The modeling of evacuation dynamics under a sudden dangerous source is an important and interesting topic in pedestrian counter flow. In this paper, an extended cellular automata model is proposed to simulate pedestrian evacuation in a channel by considering the sudden dangerous source effect, in which the concept of core radius and edge radius of dangerous source are introduced to quantitatively reflect the magnitude of the dangerous source. The parameter of influence power of pedestrian is firstly used to describe the propagation of danger information, and a new algorithm of calculating the optimal directions is presented to reflect the decisions-making behavior of pedestrian. The influences of the position, magnitude of the dangerous source and the influence power of pedestrian on evacuation process in the channel are investigated. And the spatiotemporal dynamic characteristic during the evacuation process is also discussed. The simulation results show that considering the propagation of danger information will reduce the total evacuation time considerably. Without the propagation of danger information, at the medium density, the evacuation efficiency is higher when the dangerous source is located at the side of the channel. However, at the high density, the shortest evacuation time appears when the dangerous source is located in the central partition line of the channel. Furthermore, the strength of influence power among pedestrians plays an important role on evacuation efficiency. In particular, there are important differences in the jamming mechanisms under different positions and magnitude of dangerous source.

Modeling and simulating the matching behavior of pedestrian flow at training school during the pickup period after class

Training schools widely exist in China and congestion occurs during the pickup period. However, most researches focus on investigating the pedestrian flow in classroom. In this paper, we study the adult–child matching behavior and each pedestrian’s motion (including child and adult) at a training school during the pickup period. Based on the scenario at the training school, and the features of children’s and adults’ motions, we design three strategies to describe the adult–child matching behavior, and then incorporate the matching behavior into a CA (cellular automaton) model and propose an extended CA model to study each pedestrian’s motion under each strategy during the pickup period. The numerical results indicate that each strategy has great effects on the matching behavior and the evacuation efficiency during the pickup period. The results can help administrators to design effective evacuation strategy at training school during the pickup period (especially when an emergency occurs).

Effect of uncertain information on pedestrian dynamics under adverse sight conditions

Pedestrian dynamics under adverse sight conditions is a difficult point in the field of pedestrian flow. In this paper, an extended cellular automata model is proposed to simulate pedestrian evacuation under adverse sight conditions by considering the effect of uncertain information, in which, the concept of “memory angle” is introduced to quantitatively reflect the accuracy of the evacuation information. The numerical simulations are performed to investigate the effect of the position distribution, the numbers of the memory points and the range of the view field for memory angle on the evacuation process in the room. And the spatiotemporal dynamic characteristics during the evacuation process are also discussed. The results show that the reasonable position distribution of memory points can obviously improve the evacuation efficiency and avoid the crowd caused by the pedestrian flow crash. The pedestrian evacuation efficiency is highest when the more evacuation information near the exit is obtained. In addition, when view field is poor, the accuracy of evacuation information has a significant influence on evacuation time.

Modeling and simulation of dynamic recrystallization behavior for 42CrMo steel by an extended cellular automaton method

The dynamic recrystallization (DRX) behavior of 42CrMo steel was studied by hot compressive tests and cellular automaton (CA) simulation. The experimental results showed that initial grain size besides deformation parameters has an obvious influence on dynamic recrystallization (DRX) behavior. It is found that the initial grain size not only influences the number of DRX nucleation site, but also the work-hardening (WH) coefficient, dynamic recovery (DRV) coefficient, DRX nucleation rate and grain boundary (GB) mobility. Moreover, the relationships between the WH coefficient, DRV coefficient, DRX nucleation rate, GB mobility and initial grain size can be well described by the power function. Based on the findings, the traditional CA model was extended to describe the effect of initial grain size on DRX behavior. The comparison between experimental and simulated results showed that the microstructural evolution of 42CrMo steel with different initial grain sizes during hot deformation can be accurately simulated by the extended CA model.

Study on queueing behavior in pedestrian evacuation by extended cellular automata model

This paper proposes a pedestrian evacuation model for effective simulation of evacuation efficiency based on extended cellular automata. In the model, pedestrians’ momentary transition probability to a target position is defined in terms of the floor field and queueing time, and the critical time is defined as the waiting time threshold in a queue. Queueing time and critical time are derived using Fractal Brownian Motion through analysis of pedestrian arrival characteristics. Simulations using the platform and actual evacuations were conducted to study the relationships among system evacuation time, average system velocity, pedestrian density, flow rate, and critical time. The results demonstrate that at low pedestrian density, evacuation efficiency can be improved through adoption of the shortest route strategy, and critical time has an inverse relationship with average system velocity. Conversely, at higher pedestrian densities, it is better to adopt the shortest queueing time strategy, and critical time is inversely related to flow rate.

The effect of lateral interaction on traffic flow

Abstract We propose an extended cellular automaton model for traffic flow, taking into account lateral interactions with defects and between vehicles. The fundamental diagram for a given defects density on the road is studied. It is found that the plateau size increases linearly with the decreasing road width for little defects densities. Furthermore, the capacity increases linearly with the increasing road width. However, for a fixed road width, the capacity decreases exponentially with the increasing defects density. The lateral effects for non-mutual interactions between lanes and for the same maximal velocity is also investigated. It is found that the lateral effects on one lane are meaningful only when the density on the other lane is above the critical density. However, the lateral effects are always present if fast and slow lanes exist. Little differences have been found for the mutual interactions.

Traffic accidents on a single-lane road with multi-slowdown sections

In this paper, an extended cellular automaton model is proposed to simulate the complex characteristics of traffic flow and the probability of the occurrence of traffic accidents by considering the modified conditions for determining whether traffic accidents happen and the effect of multi-slowdown sections on a highway. The simulation results show that the multi-slowdown sections can lead to multiphase coexistences (i.e. free flow phase, congestion phase and saturation phase) in traffic system. The fundamental diagram shows that the number of slowdown section does not influence the mean velocity and the mean flow under the periodic boundary condition, but the existence of slowdown sections can effectively reduce the occurrence of traffic accident. In particular, it is found that the probability of car accidents to occur is the largest at the joint of the normal-speed section and slowdown section, and the underlying mechanism is analyzed. In addition, to design the appropriate limited speed and reduce the differences between the normal speed and limited speed will alleviate traffic congestion and reduce the occurrence of traffic accidents obviously.

Analysis of train movement dynamics under various temporal–spatial constraints in fixed-block railway network using extended cellular automaton model

In the fixed-block railway traffic, the trains adjust their speeds in view of their preceding allowable spaces caused by their respective front adjacent trains or specified by scheduling commands. The railway lines have the line-type speed limits within some block sections and the point-type ones at the terminals of block sections. Those speed limits originate from line conditions, scheduling commands and indications of signal equipment. This paper attempts to in detail reveal the train movement mechanism synthetically considering those temporal–spatial constraints. The proposed train movement model defines four kinds of target points and utilizes them to successively engender the instantaneous target points with their corresponding target speeds. It adopts the rule-based description mechanism in cellular automata (CA) but with continuous spaces to replicate restrictive, autonomous and synergistic behaviors of and among trains. The selections of accelerations and decelerations are based upon the data models of practical acceleration and deceleration processes; thereupon, the model is data-driven. The analysis of train movement dynamics through case studies demonstrates that the extended CA model can reproduce the train movement mechanism of grading speed control to satisfy the aforementioned temporal–spatial constraints. The model is applicable to represent the as-is or should-be states of train movements when adjustable parameters are properly configured.

An Extended Cellular Automaton Model for Train Traffic Flow on the Dedicated Passenger Lines

As one of the key components for the railway transportation system, the Train Operation Diagram can be greatly influenced by many extrinsic and intrinsic factors. Therefore, the railway train flow has shown the strong nonlinear characteristics, which makes it quite difficult to take further relative studies. Fortunately, the cellular automaton model has its own advantages in solving nonlinear problems and traffic flow simulation. Considering the mixed features of multispeed running trains on the passenger dedicated lines, this paper presents a new train model under the moving block system with different types of trains running with the cellular automaton idea. By analyzing such key factors as the maintenance skylight, the proportion of the multispeed running trains, and the distance between adjacent stations and departure intervals, the corresponding running rules for the cellular automaton model are reestablished herewith. By means of this CA model, the program of train running system is designed to analyze the potential impact on railway carrying capacity by various factors; the model can also be implemented to simulate the actual train running process and to draw the train operation diagram by computers. Basically the theory can be applied to organize the train operation on the dedicated passenger lines.