The excluded-volume effect in microscopic pedestrian simulations

We propose a pedestrian position update rule,which is added to a microscopic pedestrian model to avoid pedestrian overlap.In the rule,the step size of a pedestrian moving in a selected direction at each update is in inverse proportion to the repulsive actions imposed by other pedestrians moving in a direction with an exponential rate.The positions of the pedestrians are then updated in each small time interval.In this way,a barrier between the pedestrians can be generated,and after updating their positions the pedestrians do not overlap with each other.The modified model is compared to the original model through a simulation of the evacuation process of pedestrians in a closed area.The simulation results indicate that the modified model is superior to the original model in several aspects.     

初始位置布局不平衡的疏散行人流仿真研究

行人初始位置布局不平衡的多安全出口疏散过程, 是行人疏散流仿真研究的热点. 利用行人流动态参数仿真模型, 在实际距离和假想距离"极大极小"路径选择机理的基础上, 改进假想距离的计算方法及其拥堵计算区域, 实现疏散过程的动态平衡; 提出行人位置布局的不平衡系数, 以描述疏散空间内行人初始位置布局的不平衡性. 从行人初始位置随机和固定布局的角度, 仿真研究正常疏散环境下行人布局的不平衡性对疏散时间的影响, 并将仿真结果与原始模型做对比分析. 研究表明, 模型能有效地实现行人流疏散过程的动态平衡, 行人疏散时间受行人位置或安全出口布局的影响较小, 而与安全出口总宽度、 行人的初始数量以及拥堵感知系数有关.     

The Korteweg-de Vires equation for the bidirectional pedestrian flow model considering the next-nearest-neighbor effect

This paper focuses on a two-dimensional bidirectional pedestrian flow model which involves the next-nearest-neighbor effect. The stability condition and the Korteweg-de Vries （KdV） equation are derived to describe the density wave of pedestrian congestion by linear stability and nonlinear analysis. Through theoretical analysis, the soliton solution is obtained.     

步行通道内行人流拉链现象的生成机理与仿真研究

以步行通道内的单向行人流为研究对象,分析研究行人拉链现象的生成机理,并建立基于Voronoi图的速度修正模型对其仿真研究.首先,从行人追求视野最佳和步行舒适的角度分析拉链现象的生成机理,以行人的视野关注和视野遮挡描述影响行人移动过程中产生拉链偏移的因素;以行人局部密度描述行人的步行舒适度;引入拉链敏感系数描述行人客观偏移的意愿程度;提出单个行人侧向偏移的机制,获得行人最佳的偏移位置.然后,构建基于Voronoi图的行人速度修正仿真模型,考虑行人是否有偏移倾向的主观意愿,并嵌入偏移规则,模拟再现行人的拉链现象.仿真发现:行人的拉链层数与通道宽度成正比,该模型速度密度关系图与实证数据吻合较好;与不考虑拉链效应相比,倾向主动进行侧向偏移的行人占比越大,越有助于提高通道内行人的移动速度、舒适度和空间利用率.     

考虑次近邻作用的行人交通格子流体力学模型

在二维双向行人交通格子流体力学模型的基础上,提出了考虑次近邻行人相互作用进行行人流优化的行人交通格子流体力学模型.通过线性稳定性分析给出新模型的稳定性条件.通过非线性分析得到描述交通堵塞密度波的改进的Korteweg-de Vries方程,并进行了数值模拟.     

成对行为对行人疏散动力学的影响研究

熟悉的行人之间经常存在着聚集运动的整体跟随行为现象.为了研究这种行为对疏散过程的影响,考虑了行人的并排成对、前后成对、混合成对三种方式,建立了一个新的元胞自动机模型,研究了三种成对方式对双出口房间内行人疏散过程的影响,并分析、讨论了不同参数下成对方式之间的差异. 关键词： 行人流 元胞自动机 成对疏散 计算机模拟     

The fundamental diagram of pedestrian model with slow reaction

The slow-to-start models are a classical cellular automata model in simulating vehicle traffic. However, to our knowledge, the slow-to-start effect has not been considered in modeling pedestrian dynamics. We verify the similar behavior between pedestrian and vehicle, and propose an new lattice gas (LG) model called the slow reaction (SR) model to describe the pedestrian’s delayed reaction in single-file movement. We simulate and reproduce Seyfried’s field experiments at the Research Centre Jülich, and use its empirical data to validate our SR model. We compare the SR model with the standard LG model. We tested different probabilities of slow reaction _ps$p_s$ in the SR model and found the simulation data of _ps=0.3$p_s=0.3$ fit the empirical data best. The RMS error of the mean velocity of the SR model is smaller than that of the standard LG model. In the range of _ps=0.1–0.3$p_s=0.1–0.3$, our fundamental diagram between velocity and density by simulation coincides with field experiments. The distribution of individual velocity in the fundamental diagram in the SR model agrees with the empirical data better than that of the standard LG model. In addition, we observe stop-and-go waves and phase separation in pedestrian flow by simulation. We reproduced the phenomena of uneven distribution of interspaces by the SR model while the standard LG model did not. The SR model can reproduce the evolution of spatio-temporal structures of pedestrian flow with higher fidelity to Seyfried’s experiments than the standard LG model.     

考虑交通出行惯例的双向行人流模型研究

推广了Baek等人最近提出的一个双向行人流模型,提出了两种改进策略,并从行人平均速度-密度关系、行人空间分布密度和位置分布等方面进行了数值分析. 研究发现,引入的两个新策略不仅可以提高行人流的平均速度,而且可以提高道路系统(尤其是道路中央区域)利用率,减轻拥堵状况,有效避免严重堵塞的发生. 改进的策略对行人的心理特点和行为特性等方面考虑更加全面,而且可以较好地模拟高密度的双向行人流. 关键词： 元胞自动机模型 双向行人流 交通惯例     

Exit selection strategy in pedestrian evacuation simulation with multi-exits

A mixed strategy of the exit selection in a pedestrian evacuation simulation with multi-exits is constructed by fusing the distance-based and time-based strategies through a cognitive coefficient, in order to reduce the evacuation imbalance caused by the asymmetry of exits or pedestrian layout, to find a critical density to distinguish whether the strategy of exit selection takes effect or not, and to analyze the exit selection results with different cognitive coefficients. The strategy of exit selection is embedded in the computation of the shortest estimated distance in a dynamic parameter model, in which the concept of a jam area layer and the procedure of step-by-step expending are introduced. Simulation results indicate the characteristics of evacuation time gradually varying against cognitive coefficient and the effectiveness of reducing evacuation imbalance caused by the asymmetry of pedestrian or exit layout. It is found that there is a critical density to distinguish whether a pedestrian jam occurs in the evacuation and whether an exit selection strategy is in effect. It is also shown that the strategy of exit selection has no effect on the evacuation process in the no-effect phase with a low density, and that evacuation time and exit selection are dependent on the cognitive coefficient and pedestrian initial density in the in-effect phase with a high density.     

线性高分子体系中高分子链间排除体积效应的模型化

提出了线性高分子体系中高分子链间排除体积效应的一个它回避模型，并且针对具体的四个模型系统进行了计算机模拟. 计算结果表明：1)线团的均方末端距〈R²〉与行走步数(N)仍然保持着与无规线团模型一样的线性关系；2)但与无规线团相比，线团的空间尺寸被压缩；3)与两侧方向的回避相比，在行走的前进方向的回避而导致的压缩效应更加明显. 关键词： 排除体积效应 回避行走 无规线团 线性高分子     

Lattice-gas simulation of escaping pedestrian flow in corridor

A lattice-gas model of biased-random walkers is used to simulate the escaping pedestrian flow under the open boundary condition in corridor. Given that the total number of people is unchanging, we have studied the evolution of pedestrian flow by varying parameters of system size. Relationships between parameters of system size and the transition time are discussed in this paper. Scaling behaviour is found as follows: the transition time t_c scales as t_c∝W^{-0.85±0.04}, and t_c∝D, where W is the width of corridor, and D is the strength of drift. However, the other parameters are found to have little influence on the transition time.     

基于演化博弈论的行人与机动车冲突演化机理研究

行人与机动车冲突时,各自都会在经过简单判断后以一定的概率选择通过.本文根据人车冲突的实际情景提出基础收益、冲突损失、等待损失以及互让损失的概念,据此构建行人与机动车的冲突博弈矩阵,并依据演化分析范式,建立人车冲突演化的动力学模型.对不同交通情形下均衡点的位置、稳定性以及系统演化机理进行深入分析,发现不同的行人与机动车的冲突损失和等待损失相对大小,对应系统的演化方向不同,可能的演化方向包括"人让车","车让人","人让车,同时车让人"以及"人不让车,车不让人".此外,定义机会损失的交通概念,据此分析系统关于行人与机动车的互让损失以及机会损失的灵敏度,发现行人或机动车互让损失的增加对于各自通过概率有着上升促进和下降抑制作用,而机会损失的作用恰好与互让损失相反.本文建立的动力学模型可以为人车冲突演化方向的宏观调控提供理论依据.     

拥堵疏散的行人拥挤力仿真研究

基于元胞自动机仿真研究拥堵疏散条件下行人拥挤力的产生、传递、吸收、抵消、累积等过程, 以安全出口前拱形的拥挤疏散行人流为研究对象, 研究拥挤致伤的生成机理. 基于行人位置距安全出口的距离, 生成趋于安全出口方向的拥挤力; 引入拥挤力效果与合力参数, 分别描述外界拥挤力对个体行人的作用效果与作用合力; 引入吸收系数与抗死伤系数, 分别描述拥挤力传递过程中行人对外界拥挤力的吸收与抵抗能力. 研究表明, 随吸收系数或抗死伤系数的增加, 能有效预防疏散行人流的拥挤致伤; 存在临界吸收系数与抗死伤系数, 将系统区分为弱保护相位、强保护相位和完全保护相位; 拥挤的死伤数量随疏散行人数量的增加而增加; 而且, 拥挤致伤的危险区域在安全出口前以安全出口中心线为对称轴呈“倒钟”形分布.     

基于元胞自动机的对向行人交通流仿真研究

基于元胞自动机对对向行人交通流进行仿真研究. 模型利用四个动态参数反映行人移动区域和其视野范围内的实际情况,从而决定行人的行为选择,行人可以根据自身周围的情况选择前进、后退、等待、左右移动、交换位置等行为. 仿真研究不同方向比例与不同系统规模的对向行人流的速度-密度、流量-密度关系. 研究结果表明,系统存在相位转换和临界密度,方向比例和系统规模对行人流的速度-密度、流量-密度关系曲线的形状和系统临界密度值有一定的影响. 关键词： 元胞自动机 对向行人流 动态参数 临界密度     

Simulation of pedestrian evacuation based on an improved dynamic parameter model

An improved dynamic parameter model is presented based on cellular automata. The dynamic parameters, including direction parameter, empty parameter, and cognition parameter, are formulated to simplify tactically the process of making decisions for pedestrians. The improved model reflects the judgement of pedestrians on surrounding conditions and the action of choosing or decision. According to the two-dimensional cellular automaton Moore neighborhood we establish the pedestrian moving rule, and carry out corresponding simulations of pedestrian evacuation. The improved model considers the impact of pedestrian density near exits on the evacuation process. Simulated and experimental results demonstrate that the improvement makes sense due to the fact that except for the spatial distance to exits, people also choose an exit according to the pedestrian density around exits. The impact factors α, β, and γ are introduced to describe transition payoff, and their optimal values are determined through simulation. Moreover, the effects of pedestrian distribution, pedestrian density, and the width of exits on the evacuation time are discussed. The optimal exit layout, i.e., the optimal position and width, is offered. The comparison between the simulated results obtained with the improved model and that from a previous model and experiments indicates that the improved model can reproduce experimental results well. Thus, it has great significance for further study, and important instructional meaning for pedestrian evacuation so as to reduce the number of casualties.     

Analysis of dynamic features in intersecting pedestrian flows

This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians' moving behavior at intersections are given as well.     

Multi-grid simulation of pedestrian counter flow with topological interaction

We investigate the dynamics of pedestrian counter flow by using a multi-grid topological pedestrian counter flow model.In the model,each pedestrian occupies multi-rather than only one grid,and interacts with others in the form of topological interaction,which means that a moving pedestrian interacts with a fixed number of those nearest neighbours coming from the opposite direction to determine his/her own moving direction.Thus the discretization of space and time are much finer,the decision making process of the pedestrian is more reliable,which all together makes the moving behaviour and boundary conditions much more realistic.When compared with field observations,it can be found that the modified model is able to reproduce well fitted pedestrian collective behaviour such as dynamical variation of lane formation,clustering of pedestrians in the same direction,etc.The fundamental diagram produced by the model fits also well with field data in the free flow region.Further analyses indicate that with the increase of the size of pedestrian counter flow system,it becomes harder for the system to transit into a jamming state,while the increase of interaction range does not change the transition point from free flow to jamming flow in the multi-grid topological counter flow model.It is also found that the asymmetry of the injection rate of pedestrians on the boundaries has direct influence on the process of transition from free flow to jamming flow,i.e.,a symmetric injection makes it easier for the system to transit into jamming flow.     

基于元胞自动机的行人视线受影响的疏散流仿真研究

基于元胞自动机对视线受影响的行人疏散流进行仿真研究.模型根据行人视野半径将疏散空间划分为可见安全出口区域、可见墙壁区域和盲目区域;利用两个动态参数描述行人在不同移动区域内的疏散特征,从而决定行人的行为选择,包括行人定向移动、沿墙移动和正常疏散移动等行为.仿真研究了行人在墙壁上存在疏散指示标志的疏散空间内,视线受影响时采用随机定向寻墙沿墙移动疏散策略的情况下,行人视野半径对行人疏散时间的影响.研究表明,行人疏散时间不仅受行人视野半径的影响,而且还与安全出口的宽度和安全出口利用率有关.     

An optimization-based overtaking model for unidirectional pedestrian flow

We propose an optimization-based model for simulating the overtaking behaviour in the unidirectional pedestrian flow. A ‘visual area’ is introduced so that agents could receive the information regarding their surroundings and react by choosing one of three options: to move straight on, to dodge to the left, or to dodge to the right. And a side preference of each pedestrian for evading and overtaking is implemented based on traffic ‘social norms’. The model was validated by reproducing the experimentally obtained pedestrian flow patterns. The effects of the initial pedestrian formation on overtaking behaviour and the evacuation time have been analysed in different geometries. The results show that pedestrian flow patterns after overtaking are obviously influenced by both the initial positions and density of the slow pedestrians in the front. Phase changes of pedestrian formation are observed in both experiment and simulations. On the other hand, for sparse pedestrian crowds, the egress time of the fast individuals is mainly impacted by the horizontal distance between the initial positions of the slow pedestrians in the front, especially in the geometry with a bottleneck.     

A modified heuristics-based model for simulating realistic pedestrian movement behavior

Pedestrian movement simulation models are used in various areas, such as building evacuation, transportation engineering, and safety management of large events. It also provides effective means to uncover underlying mechanisms of collective behaviors. In this work, a modified heuristics-based model is presented. In this model, the potential collisions in the moving process are explicitly considered. Meanwhile, a series of simulations is conducted in two typical scenarios to demonstrate the influence of critical parameters on model performance. It is found that when facing a wide obstacle in a corridor, the larger the visual radius, the earlier the pedestrian starts to make a detour. In addition, when a pedestrian observes a large crowd walking toward him, he chooses to make a detour and moves in the flow in a uniform direction. Furthermore, the model can reproduce the lane formation pedestrian flow phenomena in relatively high-density situations. With the increase of pedestrian visual radius and the weight of potential collision resistance, more stable pedestrian lanes and fewer moving-through-the-counterflow pedestrians can be observed. In terms of model validation, the density-speed relationship of simulation results accords well with that of the published empirical data. Our results demonstrate that the modified heuristics-based model can overcome the deficiency of the original model, and reproduce more realistic pedestrian movement behavior.