基于时空依赖性和注意力机制的交通速度预测

交通流精准预测对保障公共安全和解决交通拥堵具有重要的意义,在城市交通规划、交通管理、交通控制等起着重要的作用.交通预测由于其受限制于城市路网并且随着时间动态变化,其中存在着空间依赖与时间依赖,是近些年来具有挑战性的课题之一.为了同时捕获到空间和时间上的依赖,提出了一个新的神经网络:基于注意力机制的时空图卷积网络(A-TGCN).TGCN网络模型用于捕获交通数据中的动态时空特性与相关性,采用注意力机制来增强每个A-TGCN层中关键节点的信息.通过在两组数据上的实验结果表明,A-TGCN在精度以及可解释性方面都有很好的表现.     

A fast network partition method for large-scale urban traffic networks

In order to control the large-scale urban traffic network through hierarchical or decentralized methods, it is necessary to exploit a network partition method, which should be both effective in extracting subnetworks and fast to compute. In this paper, a new approach to calculate the correlation degree, which determines the desire for interconnection between two adjacent intersections, is first proposed. It is used as a weight of a link in an urban traffic network, which considers both the physical characteristics and the dynamic traffic information of the link. Then, a fast network division approach by optimizing the modularity, which is a criterion to distinguish the quality of the partition results, is applied to identify the subnetworks for large-scale urban traffic networks. Finally, an application to a specified urban traffic network is investigated using the proposed algorithm. The results show that it is an effective and efficient method for partitioning urban traffic networks automatically in real world.     

基于多学科设计优化的路网交通分布式协同控制

城市路网交通控制直接影响着交通运行效率,对其优化研究已成为缓解城市交通拥堵问题的热点之一.鉴于此,针对高峰交通路网将其分为过饱和区域与过饱和关联区域,在采用灰色关联分析-谱聚类方法对关联区域划分的基础上,构建路网交通分布式协同控制模型,进一步提出基于多学科设计优化的过饱和区域及其关联区域协同优化求解方法.通过搭建实例路网模型分析算法优化效果,结果表明所提出方法能够明显改善路网交通运行效率,有助于缓解城市通勤高峰时段的交通拥堵和扩散问题.     

Distributed Model Predictive Control Method for Optimal Coordination of Signal Splits in Urban Traffic Networks

Coordination and control approaches based on model predictive control (MPC) have been widely investigated for traffic signal control in urban traffic networks. However, due to the complex non‐linear characters of traffic flows and the large scale of traffic networks, a basic challenge faced by these approaches is the high online computational complexity. In this paper, to reduce the computational complexity and improve the applicability of traffic signal control approaches based on MPC in practice, we propose a distributed MPC approach (DCA‐MPC) to coordinate and optimize the signal splits. Instead of describing the dynamics of traffic flow within each link of the traffic network with a simplified linear model, we present an improved nonlinear traffic model. Based on the nonlinear model, an MPC optimization framework for the signal splits control is developed, whereby the interactions between subsystems are accurately modeled by employing two interconnecting constraints. In addition, by designing a novel dual decomposition strategy, a distributed coordination algorithm is proposed. Finally, with a benchmark traffic network, experimental results are given to illustrate the effectiveness of the proposed method.     

基于有向含权复杂网络的城市交通路网关键路段识别

针对目前基于复杂网络识别城市交通路网关键路段缺乏考虑现实影响因素和路段方向性问题,提出了一种基于有向含权复杂网络的关键路段识别方法。第一阶段利用复杂网络理论将城市交通路网构建成有向含权复杂网络模型;第二阶段利用LinkRank算法对复杂网络中边进行重要度排序,以此识别关键边,即城市交通路网关键路段;第三阶段利用变异的易感—感染（susceptible-infective,SI）模型对关键路段进行影响评估。通过对浙江省海宁市城区的城市交通路网分析,验证了方法的实用性和有效性。     

考虑时空影响下的图卷积网络短时交通流预测

针对交通流预测过程中城市道路路网的空间特征难以充分提取,导致预测结果精度不高的问题,提出图卷积网络（GCN）与门控循环单元（GRU）组合短时交通流预测模型。利用GCN对拓扑结构数据处理的优势,将城市道路路网空间排列结构转换为拓扑关系建模,通过解决拓扑关系问题有效提取出路网间的空间特征。采用GraphSAGE算法改进GCN模型,通过加和聚合算子和图注意力机制（GAT）聚合空间特征,将包含空间特征的输出作为GRU模型的输入提取时间特征。利用真实道路车流量数据进行模型验证,结果表明该模型相较于不具有GCN的模型预测准确率提升约8%,均方误差缩小约0.010?37,说明所提模型具有相对较高的稳定性及预测精度,可以为大型城市路网提供重要的交通诱导依据。     

城市交通网络宏观控制模型及仿真实现

为研究适合城市交通网络控制系统应用的交通流预测模型,在改进Van Den Berg, M的路段交通流模型的基础上,建立了以路口交通流为基本建模单元,以动态非线性离散方程反映交通流变化的城市交通网络宏观模型.为验证该模型能有效地预测城市路网的交通流信息,在VC++net环境下,开发了城市交通宏观控制模型仿真系统UTFS,设计了网络拓扑结构模块,以适应不同规模、不同复杂程度的实际交通网络的仿真要求.最后选取典型网络进行应用研究.仿真结果表明:该模型满足交通控制对控制模型的实时性和精度要求,该仿真系统可以作为城市交通网络宏观控制模型验证的有效工具,也可以作为城市交通控制系统控制和优化研究的辅助工具.     

基于灰色神经网络的空中交通流量预测方法

空中交通流量预测是空中交通管理领域的研究热点。针对空中交通流量的复杂性、非线性和不确定性,提出一种基于灰色神经网络算法进近空域内的空中交通流量预测方法。将灰色系统与人工神经网络相结合构成的灰色神经网络预测模型,优于单一的灰色预测方法和人工神经网络预测方法。     

Urban traffic congestion propagation and bottleneck identification

Bottlenecks in urban traffic network are sticking points in restricting network collectivity traffic efficiency. To identify network bottlenecks effectively is a foundational work for improving network traffic condition and preventing traffic congestion. In this paper, a congestion propagation model of urban network traffic is proposed based on the cell transmission model （CTM）. The proposed model includes a link model, which describes flow propagation on links, and a node model, which represents link-to-link flow propagation. A new method of estimating average journey velocity （AJV） of both link and network is developed to identify network congestion bottlenecks. A numerical example is studied in Sioux Falls urban traffic network. The proposed model is employed in simulating network traffic propagation and congestion bottleneck identification under different traffic demands. The simulation results show that continual increase of traffic demand is an immediate factor in network congestion bottleneck emergence and increase as well as reducing network collectivity capability. Whether a particular link will become a bottleneck is mainly determined by its position in network, its traffic flow （attributed to different OD pairs） component, and network traffic demand.     

Traffic signal timing using two-dimensional correlation,neuro-fuzzy and queuing based neural networks

Optimizing the traffic signal control has an essential impact on intersections efficiency in urban transportation. This paper presents a two-stage method for intersection signal timing control. First, the traffic volume is predicted using a neuro-fuzzy network called Adaptive neuro-fuzzy inference system (ANFIS). The inputs of this network include two-dimensional, hourly and daily, traffic volume correlations. In the second stage, appropriate signal cycle and optimized timing of each phase of the signal are estimated using a combination of Self Organizing and Hopfield neural networks. The energy function of the Hopfield network is based on a traffic model derived by queuing analysis. The performance of the proposed method has been evaluated for real data. The two-dimensional correlation presents superior performance compared to hourly traffic correlation. The evaluation of proposed overall method shows considerable intersection throughput improvement comparing to the results taken form Synchro software.     

Traffic modeling, prediction, and congestion control for high-speednetworks: a fuzzy AR approach

In this study, a fuzzy autoregressive (fuzzy-AR) model is proposed to describe the traffic characteristics of high-speed networks. The fuzzy-AR model approximates a nonlinear time-variant process with a combination of several linear local AR processes using a fuzzy clustering method. We propose that the use of this fuzzy-AR model has greater potential for congestion control of packet network traffic. The parameter estimation problem in fuzzy-AR modeling is treated by a clustering algorithm developed from actual traffic data in high-speed networks. Based on the adaptive AR-prediction model and queueing theory, a simple congestion control scheme is proposed to provide an efficient traffic management for high-speed networks. Finally, using the actual Ethernet-LAN packet traffic data, several examples are given to demonstrate the validity of this proposed method for high-speed network traffic control     

城市快速路网匝道与污染控制双层多目标规划模型

基于环境容量和交通容量,建立了一个双层多目标规划模型描述城市快速道路网的污染控制与匝道控制,并考虑了用户的路径选择行为．设计了基于改进遗传算法的启发式求解算法。该算法借助不可微精确罚函数将约束问题转化为单个无约束问题来解决,采用混合杂交和间歇变异提高算法的搜索能力．最后。通过算例说明该模型及算法的有效性．     

基于节点状态一致的路网边界控制

针对路网车流分布不均衡的问题,本文提出基于一致性思想的路网边界流量控制策略.首先,基于车辆守恒宏观模型,描述了区域边界车流的动态演化;以区域内路段占有率一致作为控制目标,边界交叉口配时参数为控制输入,进行区域边界反馈控制设计,并推导出边界车流输入与内部路段放行比例的解析关系;最后,通过路网实测数据验证了边界控制策略的适用性.结果表明:边界控制策略不仅能够有效改善路网交通流分布不均衡的状况,还能够有效降低路网的平均延误、排队长度等指标,提高路网运行效率.     

基于网络节点输出速率调节的非线性拥塞控制及稳定性鲁棒性分析

该文针对计算机高速互联网中最大服务交通流即能控交通流的拥塞调节问题,提出了一种基于网络节点输出速率调节的非线性拥塞控制机制并对其进行了稳定性和鲁棒性分析。克服了传统的基于输入端控制需要信源端和传输通道多重支持的约束。在单个节点的业务流模型基础上,将信源输入视为系统的扰动,通过调节输出速率来控制节点队列稳定。运用OPNET仿真软件对其进行了不同输入和工作条件下的仿真,结果显示,在所设计的非线性模糊PID队列控制机制下,队列稳定性好且具有较好的鲁棒性和抗干扰性。     

基于CPN的城市智能交通信号控制系统建模

提出了一种城市交通控制系统的分布式结构及控制策略，介绍了CPN(Colorcd Petrj Nets)的基本概念及建模特性，着重探讨了借助CPN建模技术对城市智能交通信号控制系统进行的建模分析。     

基于深度时空残差网络的路网短时交通流预测

针对城市路网短时交通流预测受到许多复杂因素的影响,提出一种基于深度时空残差网络的路网短时交通流预测模型DST-Res Net（deep spatio-temporal residual network）。针对时空数据的两个独特属性邻近性和周期性分别设计相应的残差网络分支,通过为两个分支中相同的道路分配不同的权重动态聚合两个分支网络的输出,调整时空属性对不同路段交通流预测的影响程度,将两个残差网络的聚合结果与外部因素进行融合。通过选择RMSE和R²为模型的评价指标进行实验验证,该DST-ResNet模型相较主流的LSTM模型具有更高的有效性和可行性。     

城市复杂道路网络交通流的分解模型

针对城市道路交通流非线性、不确定性和模糊性特点,将城市道路与快速干道作为整体对待,提出了面向控制应用的城市交通网络宏观动态离散模型。将城市街区作为划分基点,把整个城市道路复杂交通网络分解为交叉口和单向环形道路两个子系统,分别建立了它们的宏观动态模型。通过对交叉口进行理想虚拟变形,将各个单向环形道路连接在一起,从而形成各种复杂网络。对西安市中心区域的实际交通流数据进行了仿真研究,结果表明该交通流模型基本实现了城市道路与快速干道的统一分析建模,较好地反映了城市路网的交通流信息,可以作为城市交通控制系统分析和设计的有力工具。     

一种基于神经网络的多节点非线性PID队列控制

针对异步传输模式(ATM)网络可利用比特率(ABR)业务流多数都具有突发性,往往会造成网络过载,甚至引起严重的网络拥塞问题,提出了一种基于BP神经网络的缓冲队列的非线性控制机制并对其进行了抗扰性分析。在多节点的业务流模型基础上,运用OPNET软件对其进行了不同工作条件下的仿真,结果显示,在所设计的控制机制下,网络的有关性能良好。     

基于轨迹大数据的动态最优路径规划

以轨迹大数据为基础,结合城市交通状态与用户个性化需求,提出一种基于改进Viterbi算法的动态最优路径规划算法。首先融合交通状态和真实路网拓扑结构,构建基于有向多重加权复杂网络的交通网络模型。采用基于层次分析法和熵权法相结合的综合赋权法对交通网络模型的多权重属性进行权重分配,得到新的有向加权复杂网络模型。进一步采用改进的Viterbi算法求解最优路径。最后,以兰州市为例,对最优路径规划进行分析,并将该算法与静态规划方法进行比较,验证城市最优路径规划算法的有效性与实时性。实验结果表明,结合城市交通状态与用户偏向的路径规划更加科学合理,能够为兰州市驾车出行、交通管理部门决策提供决策支持和参考。     

Macroscopic fundamental diagram in simple model of urban traffic

Macroscopic fundamental diagram (MFD) is a reproducible unimodal relation between average vehicle density and average flow rate in urban traffic. Although this idea is tested by a few observations and simulations, its mechanism is not well understood. In order to understand it, a simple graph-based model of urban traffic is proposed. MFDs in our model system are investigated numerically for grid networks. It is found that MFDs in our system are discontinuous, which is inconsistent with the observation of real urban traffic.