Lattice hydrodynamic model of pedestrian flow considering the asymmetric effect

The original lattice hydrodynamic model of traffic flow is extended to single-file pedestrian movement at middle and high density by considering asymmetric interaction (i.e., attractive force and repulsive force). A new optimal velocity function is introduced to depict the complex behaviors of pedestrian movement. The stability condition of this model is obtained by using the linear stability theory. It is shown that the modified optimal velocity function has a remarkable influence on the neutral stability curve and the pedestrian phase transitions. The modified Korteweg-de Vries (mKdV) equation near the critical point is derived by applying the reductive perturbation method, and its kink-antikink soliton solution can better describe the stop-and-go phenomenon of pedestrian flow. From the density profiles, it can be found that the asymmetric interaction is more efficient than the symmetric interaction in suppressing the pedestrian jam. The numerical results are consistent with the theoretical analysis.     

A Lane-Based Optimization Method for Minimizing Delay at Isolated Signal-Controlled Junctions

This paper presents a lane-based optimization method for minimizing delay at isolated signal-controlled junctions. The method integrates the design of lane markings and signal settings, and considers both traffic and pedestrian movements in a unified framework. While the capacity maximization and cycle length minimization problems are formulated as Binary-Mix-Integer-Linear-Programs (BMILPs) that are solvable by standard branch-and-bound routines, the problem of delay minimization is formulated as a Binary-Mix-Integer-Non-Linear Program (BMINLP). A cutting plane algorithm and a heuristic line search algorithm are proposed to solve this difficult BMINLP problem. The integer variables include the permitted movements on traffic lanes and successor functions to govern the order of signal displays, whereas the continuous variables include the assigned lane flows, common flow multiplier, cycle length, and starts and durations of green for traffic movements, lanes and pedestrian crossings. A set of constraints is set up to ensure the feasibility and safety of the resultant optimized lane markings and signal settings. A numerical example is given to demonstrate the effectiveness of the proposed methodology. The heuristic line search algorithm is more cost-effective in terms of both optimality of solution and computing time requirement. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于预判发货的网络零售商双模式批量配送研究

基于预判发货的背景,考虑订单处理中心和配送站之间存在第三方物流和自营物流两种配送模式,研究了B2C网络零售商的动态批量配送问题。首先利用混合整数规划构建了一个三级供应链系统下的动态批量配送模型,接着采用网络流规划的技术重新建模,并在其基础上对最优解的性质进行了分析,进而设计了计算时间复杂度为O(T²)的精确动态规划求解算法。最后用算例实验验证了该算法的有效性和适用性。     

An algorithm to assign pedestrian groups dispersing at public gatherings based on pedestrian-traffic modelling

The minimization of weighted pedestrian and vehicle times for pedestrians dispersing at public gatherings is considered. An algorithm to solve this problem and to assign each pedestrian group to a unique selected path is developed. This algorithm considers general network where its arc values are dependent on pedestrian/traffic modelling and its nodes (intersections) have penalties.The algorithm is followed by a case study which exhibits possible pedestrian/traffic models. These experimental models yield some deterministic functional dependency between pedestrians' speed and sidewalk concentration, pedestrians' street concentration, and sidewalk concentration, and vehicles' speed and pedestrians' street concentration. If such and realistic models serve as an input to the algorithm it might contribute to reduce pedestrian/traffic conflicts and interference and hence to increase the overall safety of these two travel modes.     

Optimizing the release of passenger flow guidance information in urban rail transit network via agent-based simulation

The passenger flow guidance is an effective demand management strategy to alleviate the excessive congestion in the urban rail transit network. In order to determine the scope and the timing, a simulation-based optimization model is proposed to optimize the release of passenger flow guidance information in the rail transit network in this paper. In the optimization model, we mainly focus on three aspects namely; where, when and what type of the guidance information should be released to the passengers. In the simulation model, the passenger choice behavior is captured by the agent-based simulation method, which responses to the congestion and the guidance information. Based on this, the dynamic passenger flow distribution can be derived. Furthermore, the adoption rate of the displayed guidance information on passenger information system as well as its impact on passenger travel behavior are also considered in the model. A hybrid heuristic solution algorithm, integrated with passenger simulator and genetic algorithm, is developed to solve the proposed simulation-based optimization model. Finally, a case study of Beijing subway is carried out with the large-scale smart card data. The numerical study shows that the passenger flow demand affects the guidance effect significantly and the best guidance effect can be met with sufficiently high passenger flow demand. And the guidance rate is also found to affect the guidance results. The results also show that the proposed model can provide a detailed guidance scheme for every station at selected time intervals. The results show that the dynamic releasing scheme can save up to a total of 46,319 min in passenger travel time during a single guidance period.     

基于交通流的多模糊时间窗车辆路径优化

研究了基于交通流的多模糊时间窗车辆路径问题,考虑了实际中不断变化的交通流以及客户具有多个模糊时间窗的情况,以最小化配送总成本和最大化客户满意度为目标,构建基于交通流的多模糊时间窗车辆路径模型。根据伊藤算法的基本原理,设计了求解该模型的改进伊藤算法,结合仿真算例进行了模拟计算,并与蚁群算法的计算结果进行了对比分析,结果表明,利用改进伊藤算法求解基于交通流的多模糊时间窗车辆路径问题,迭代次数小,效率更高,能够在较短的时间内收敛到全局最优解,可以有效的求解多模糊时间窗车辆路径问题。     

Dynamic navigation field in the social force model for pedestrian evacuation

This paper presents a generalized walking cost distribution to determine a dynamic navigation field in the social force model for pedestrian evacuation. The local walking cost per unit distance of movement includes the cost associated with travel time and other additional costs incurred by pedestrians to avoid colliding with obstacles in a dynamic environment. In the dynamic navigation field, pedestrians expect to choose an optimal path with the lowest walking cost to reach their target destination reactively based on available instantaneous information. The social force model with the dynamic navigation field is validated by comparing the simulation results with empirical observations. The fundamental diagrams for observations and simulation data agree well, which indicates the effectiveness of the model. Numerical results show that the model with the dynamic navigation field can reproduce typical stages of the dynamics of pedestrian evacuation, such as self-organized arching and queuing phenomena, and can capture the route choice and exit choice behaviors of pedestrians during the evacuation process. Compared to the model with the static navigation field, the model with the dynamic navigation field can reduce the total evacuation time of the room and save the required CPU time for a large group of pedestrians. Furthermore, the strong tendency to avoid local high-density regions (i.e., minimizing collisions) can also reduce the total evacuation time under the same conditions.     

Particle methods for multi-group pedestrian flow

We consider a multi-group microscopic model for pedestrian flow describing the behaviour of large groups. It is based on an interacting particle system coupled to an eikonal equation. Hydrodynamic multi-group models are derived from the underlying particle system as well as scalar multi-group models. The eikonal equation is used to compute optimal paths for the pedestrians. Particle methods are used to solve the equations on all levels of the hierarchy. Numerical test cases are investigated and the models and, in particular, the resulting evacuation times are compared for a wide range of different parameters.     

An equivalent moving force model for consideration of human-structure interaction

To predict the vibration response of footbridges, many codes of practice use a deterministic moving force (MF) model. This approach may not be well suited for the design of slender, lightweight, low-damping, and low-frequency footbridges because it ignores the pedestrian interaction with the vibrating footbridge. On the other hand, a spring-mass-damper (SMD) model is able to incorporate human mass, stiffness, and damping into the vibration response prediction. However, the SMD model is computationally demanding and not commonly available in engineering practice. To address this shortfall, a framework is proposed to derive a computationally-efficient equivalent MF-structure system to the reference SMD-structure system such that both systems give a similar vibration response metric. Analytical and numerical approaches to the equivalent MF (EMF) system are described in detail and applied to bridges with approximately simply-supported mode shapes. A sensitivity analysis is carried out to show the effects of different pedestrian parameters on the equivalent damping of the EMF system. The effects of pedestrian damping, frequency, and weight are found to be pronounced, while those of dynamic load factors and pedestrian step length are insignificant. Finally, empirical expressions are proposed in a probabilistic framework to determine the equivalent damping for simply-supported low-frequency footbridges as a function of bridge frequency. This work should find use in the serviceability assessment of low-frequency footbridges in engineering practice.     

Multi-variable grey model based on dynamic background algorithm for forecasting the interval sequence

The multi-variable grey model based on dynamic background algorithm improves the forecasting performance of the multi-variable grey model on the precise number sequence. In order to make this model suitable for the interval sequence, the matrix form of the multi-variable grey model based on dynamic background algorithm is proposed in the paper. In the modeling process, the interval is treated as a two-dimensional column vector, the parameters of the multi-variable grey model are replaced by matrices, and the dynamic background algorithm for interval sequences is proposed. The analysis results of the matrix algorithm for the dynamic background value and the prediction formula show that the new model is essentially a way to predict one of the two bounds of an interval by combining them, reflecting the integrity and interaction between the lower and upper bounds. The interval predictions of industrial electricity consumption of Zhejiang Province, China national electricity consumption and consumer price index show that the new model can well predict the minimum and maximum values of the interval sequence and has better prediction performance compared with the method of predicting each boundary sequence separately.     

Modeling framework for optimal evacuation of large-scale crowded pedestrian facilities

The paper presents a simulation–optimization modeling framework for the evacuation of large-scale pedestrian facilities with multiple exit gates. The framework integrates a genetic algorithm (GA) and a microscopic pedestrian simulation–assignment model. The GA searches for the optimal evacuation plan, while the simulation model guides the search through evaluating the quality of the generated evacuation plans. Evacuees are assumed to receive evacuation instructions in terms of the optimal exit gates and evacuation start times. The framework is applied to develop an optimal evacuation plan for a hypothetical crowded exhibition hall. The obtained results show that the model converges to a superior optimal evacuation plan within an acceptable number of iterations. In addition, the obtained evacuation plan outperforms conventional plans that implement nearest-gate immediate evacuation strategies.     

不同行为风格下路段行人与机动车行为博弈分析

针对路段过街行人与机动车的博弈决策行为,考虑不同交通行为风格下行人的过街特征和驾驶人的驾驶行为习惯等影响因素,开展路段行人交通行为风格调查,掌握不同交通行为风格下路段行人的过街特征,构建非合作动态人车博弈模型.通过分析不同策略下行人与驾驶人的收益,求解纳什均衡,得到不同策略下行人与驾驶人的最优策略.为解决路段行人与机动车冲突提供新的思路.     

A neural network model for enhanced operation of midblock signalled pedestrian crossings

UK transport policy has shifted dramatically in recent years. The new policy direction to promote walking as an alternative to car for short trips. Midblock signalled pedestrian crossings are a common method of resolving the conflict between pedestrians and vehicles. This paper considers alternative operating strategies for midblock signalled pedestrian crossings that are more responsive to the needs of pedestrians without increasing the delay to motorists and freight traffic. A succession of artificial neural network (ANN) models is developed and factors influencing the performance of pedestrian gap acceptance models both in terms of accuracy and processing requirements are considered in detail. The paper concludes that a feedforward ANN using backpropagation can deliver a gap acceptance model with a high degree of accuracy with acceptable constraints.     

On the modeling of pedestrian motion

A model for the simulation of pedestrian flows and crowd dynamics has been developed. The model is based on a series of forces, such as: will forces (the desire to reach a place at a certain time), pedestrian collision avoidance forces, obstacle/wall avoidance forces; pedestrian contact forces, and obstacle/wall contact forces. Except for the will force, it is assumed that for any given pedestrian these forces are the result of only local (nearest neighbour) situations. The near-neighbour search problem is solved by an efficient incremental Delaunay triangulation that is updated at every timestep. In order to allow for general geometries a so-called background triangulation is used to carry all geographic information. At any given time the location of any given pedestrian is updated on this mesh. The results obtained to date show that the model performs well for standard benchmarks, and allows for typical crowd dynamics, such as lane forming, overtaking, avoidance of obstacles and panic behaviour.     

Macroscopic attraction-based simulation of pedestrian mobility: A dynamic individual route-choice approach

This paper presents a dynamic distribution and assignment simulation model based on discrete time simulation techniques and dynamic route assignment for planning, engineering design, and operation analysis of big exhibition events from a pedestrian circulation perspective. Both, the distribution and assignment stages are incorporated in an interlaced way with a dynamic behavior along a specific time horizon. In the proposed model, the individual route choice is dynamically determined as consequence of facilities attractiveness and network congestion. Therefore, in contrast with other simulation approaches, it does not require the usual origin–destination trip matrices to describe the transportation demand or the specification of different paths to be followed by visitors. This modeling approach turns out to be very appropriate for the simulation of these big exhibition events where each visitor usually has multiple and a priori unordered destination choices after entering the scenario.     

Dynamic Network Flow with Uncertain Arc Capacities: Decomposition Algorithm and Computational Results

In a multiperiod dynamic network flow problem, we model uncertain arc capacities using scenario aggregation. This model is so large that it may be difficult to obtain optimal integer or even continuous solutions. We develop a Lagrangian decomposition method based on the structure recently introduced in G.D. Glockner and G.L. Nemhauser, Operations Research, vol. 48, pp. 233–242, 2000. Our algorithm produces a near-optimal primal integral solution and an optimum solution to the Lagrangian dual. The dual is initialized using marginal values from a primal heuristic. Then, primal and dual solutions are improved in alternation. The algorithm greatly reduces computation time and memory use for real-world instances derived from an air traffic control model.     

On validation of SigmaEva pedestrian evacuation computer simulation module with bottleneck flow

This article is focused on dynamics of the computer simulation module SigmaEva in bottlenecks. Unidirectional flow was considered. The module SigmaEva realizes the discrete-continuous stochastic pedestrian dynamics model SIgMA.DC that is shortly presented here. Specific and full flow rates for different bottleneck width are given in comparison with experimental data.     

考虑城市住房分布的二维连续型动态交通分配模型及其污染物排放估计

将城市交通路网抽象为二维连续的平面,提出一个考虑城市住房分布的二维连续型动态交通分配模型,并估计了城市交通污染物排放水平.该模型中,住房分布影响交通需求,出行者根据用户最优准则选择出发时间和路径,可以用于模拟城市交通运行的动态演化过程,得到密度、速度和流量等物理量.采用基于车辆速度和加速度的微观污染物排放模型VT-micro估计城市交通CO2动态排放水平.基于三角网格,采用有限体积法、投影算法和相继平均法进行数值求解,给出一个数值算例验证了模型和算法的有效性.     

交通流流体力学模型与非线性波

介绍了交通流问题中的流体力学描述方法,分析了交通流在受压力和自驱动力等因素作用下所产生的非线性波动现象．这些描述包括LWR运动学模型,考虑动力学效应的高阶模型,考虑超车效应的多车种LWR(Lighthill-Whitham-Richards)模型,以及考虑流通量间断的模型方程．此外,还介绍了LWR网络推广模型在交叉口的Riemann问题求解;提出了描述二维行人流问题的Navier-Stokes-Eikon方程模型并描述了确定行人流运动期盼方向的基本思想．     

Model reduction on inertial manifolds for N–S equations approached by multilevel finite element method

Approximate Inertial Manifolds (AIMs) is approached by multilevel finite element method, which can be referred to as a Post-processed nonlinear Galerkin finite element method, and is applied to the model reduction for fluid dynamics, a typical kind of nonlinear continuous dynamic system from viewpoint of nonlinear dynamics. By this method, each unknown variable, namely, velocity and pressure, is divided into two components, that is the large eddy and small eddy components. The interaction between large eddy and small eddy components, which is negligible if standard Galerkin algorithm is used to approach the original governing equations, is considered essentially by AIMs, and consequently a coarse grid finite element space and a fine grid incremental finite element space are introduced to approach the two components. As an example, the flow field of incompressible flows around airfoil is simulated numerically and discussed, and velocity and pressure distributions of the flow field are obtained accurately. The results show that there exists less essential degrees-of-freedom which can dominate the dynamic behaviors of the discretized system in comparison with the traditional methods, and large computing time can be saved by this efficient method. In a sense, the small eddy component can be captured by AIMs with fewer grids, and an accurate result can also be obtained.