一种基于收费数据的断面流量估算方法

高速公路的流量是反映高速公路交通状态的一个重要参数.目前,针对高速公路断面流量的采集主要依靠人工方式或者通过安装一些车流检测设备来获得,成本较高.结合高速公路收费系统的特点,通过对收费数据的统计分析,提出一种基于收费数据估算高速公路断面流量的方法.首先,对收费数据进行初步的处理,从中计算出行驶时间;然后,根据收费数据中的车辆信息统计出各个OD的交通流量;最后,结合各个收费站出入口的位置信息、路段行驶速度信息以及OD流量来估算断面的交通流量.     

基于手机信令大数据的城市居民出行OD预测

为得到具有客观性、动态性的居民出行起止点间交通出行量(OD trips),以中国移动手机信令大数据为基础,阐述了手机信令数据的来源与构成,针对城市居民出行目的,通过数据分析,设置10分钟为划分出行活动的阈值,提出基于手机信令数据获得的OD矩阵的原理与方法,应用数据挖掘技术,对贵阳市居民出行OD矩阵进行了预测.为进一步加强大数据与城市智能交通系统的融合,将得到的城市居民出行OD矩阵应用到真实的城市公交线网中.最后通过MicroCity平台,将数据结果实现可视化.分析结果表明:与传统OD调查方式相比,利用手机信令大数据获得的OD矩阵客观性、动态性较强,信息采集分析周期短,更容易与城市智能交通系统融合,应用可视化平台,可实时反映出城市公交运营状态,为城市智能规划和调度提供重要参考.     

循环矩阵本原指数的上界估计

本文给出了循环矩阵本原指数上界的新的估计及一种由级数较低的循环矩阵的本原指数估计级数较高的循环矩阵的本原指数的方法，解决了一类循环矩阵本原指数的计算问题．     

协方差阵估计的比较

本文在一般线性回归模型误差异方差情况下，通过计算机模拟对回归系数最小二乘估计的协方差矩阵的估计进行了比较。结果表明，当样本大小大于50时，回归系数的最小二乘估计具有较高的估计精度；其协方差矩阵的五种估计以普通最小二乘估计的协方差矩阵为最优。     

推广的生长曲线模型的协方差不变最小二乘无偏估计(Ⅱ)

本文用投影理论及矩阵的谱分解方法，找出了推广的生长曲线模型的未知协方差矩阵∑及tr（C∑）在一定条件下的不变最小二乘无偏估计，为其估计的优良性的讨论奠定基础。     

连续时间非时齐马氏过程的广义Dobrushin系数的估计

本文研究了非时齐马氏过程的广义Dobrushin系数的估计问题.在将经典Dobrushin遍历系数推广为加权的遍历系数的基础上,利用了矩阵拆分的方法,得到了对这种广义遍历系数的估计方法,推广了时齐马氏过程关于遍历系数的估计结果,借此可进一步得到有关遍历性的判定结论.     

关于复正定矩阵乘积迹的估计

讨论了复正定矩阵乘积迹的估计式，得到了一系列估计复正定矩阵乘积迹的不等式。     

高阶矩阵分块降阶求算法

高阶矩阵分块降阶求算法龚清礼（西南工学院）用矩阵的理论和方法处理现代工程技术中的各种问题已越来越普遍，计算或估计矩阵的秩，是矩阵论不可缺少的内容，高阶矩阵秩的计算是很麻烦，文献［１］提出了用分块降阶计算高阶矩阵秩的方法，对简化计算有一定的效果。但计算...     

增长曲线模型中UMRE估计的存在性

对于设计矩阵不满秩，协方差阵任意或具有均匀结构或序列结构的正态增长曲线模型，本文讨论参数矩阵的一致最小风险同变（UMng）估计的存在性．在仿射变换群GI和转移交换群、二次损失和矩阵损失下本文分别获得存在回归系数矩阵的线性可估函数矩阵的UMRE估计的充要条件，推广了由[21]给出的在设计矩阵满秩下估计回归系数矩阵的结果．本文还首次证明了在群G1和二次损失下不存在协方差阵V和trV的UMRE估计．     

路段容量约束弹性需求交通均衡分配近似算法

本文研究了带路段容量约束弹性需求用户均衡交通分配问题及其近似解法.采用超需求模型将弹性需求转化为固定需求,提出了一种带路段容量约束弹性需求用户均衡交通分配近似算法.该算法在迭代过程中,通过不断自适应调节排队延误因子、误差因子来近似真实路段行驶时间,使路段流量逐步满足约束条件,最终达到广义用户均衡.这种方法克服了容量约束弹性需求用户均衡分配计算量大及随机分配法要求枚举所有路径的困难.随后证明了算法的收敛性,并对一个小型路网进行了数值试验.     

Estimating the urban OD matrix: A neural network approach

In this paper, the Hopfield Neural Network (HNN) model is used to estimate the urban Orientation-Destination (OD) distribution matrix from the link volumes of the transportation network, so as to promote the solving speed and precision.     

双模式交通网络中的ATIS信息定价研究

先进的出行者信息系统(ATIS)是一种服务商品,已有的研究多从提高市场占有率的角度对单模式交通网络中的ATIS进行信息定价。多模式交通网络中影响ATIS市场占有率的因素众多,而且ATIS的提供成本往往与信息质量和使用规模同时相关。因此,信息定价问题应从ATIS服务提供商利润最大化的角度进行研究。本文把ATIS信息的单次使用费用和ATIS的信息质量同时作为决策变量,将双模式路网中ATIS的定价问题描述为一个双层规划模型。其中,混合用户均衡模型为下层模型,收益模型为上层模型。然后,基于上海市虹口区的路网数据,对下层模型进行了数值分析,并讨论了相关经济效益问题。此外,本文提出了求解下层模型的MSAF算法,并进一步嵌套了粒子群(PSO)算法,最终得到ATIS服务提供商的最优ATIS信息定价和信息质量提供方案。     

A fuzzy set-based approach to origin–destination matrix estimation in urban traffic networks with imprecise data

An important issue in the management of urban traffic networks is the estimation of origin–destination (O–D) matrices whose entries represent the travel demands of network users. We discuss the challenges of O–D matrix estimation with incomplete, imprecise data. We propose a fuzzy set-based approach that utilises successive linear approximation. The fuzzy sets used have triangular membership functions that are easy to interpret and enable straightforward calibration of the parameters that weight the discrepancy between observed data and those predicted by the proposed approach. The method is potentially useful when prior O–D matrix entry estimates are unavailable or scarce, requiring trip generation information on origin departures and/or destination arrivals, leading to multiple modelling alternatives. The method may also be useful when there is no O–D matrix that can be user-optimally assigned to the network to reproduce observed link counts exactly. The method has been tested on some numerical examples from the literature and the results compare favourably with the results of earlier methods. It has also been successfully used to estimate O–D matrices for a practical urban traffic network in Brazil.     

A ternary-arithmetic topological based algebraic method for networks traffic observability

In this paper an algebraic method, which shares all the advantages of the topological methods and allows us to obtain the same results as the standard algebraic method with a substantial reduction in memory and cpu requirements, is presented. The main idea consists of writing the link, OD and scanned flows in terms of route instead of OD flows. This alternative permits starting the algebraic and topological processes with identical matrices of zeros and ones. In addition, in most iterations the pivots can be selected in such a way that the resulting matrices after each iteration contain only zeroes, ones and minus ones. This allows us to design a ternary arithmetic which reproduces the algebraic results exactly, requires only two bits to store each matrix entry and have no precision or non-zero pivot identification problems. Only when this process cannot be continued, the pure algebraic method is used, but only with a very reduced size matrix when compared with the size of the initial matrix. The method is illustrated by its application to a very simple network and to a real network example (the city of Cuenca, Spain).     

New algorithmic alternatives for the O–D matrix adjustment problem on traffic networks

In the last years the O–D matrix adjustment problem using link counts on a traffic network modelled by means of a static user equilibrium approach has been formulated advantageously by means of bilevel programs. The algorithms developed to solve the problem present heuristic components in a lesser or greater degree. In this paper two new algorithmic alternatives are presented for this problem. The first alternative is an hybrid scheme proximal point-steepest descent that is based on a development of Codina for the approximation of the steepest descent direction of the upper level function and the second alternative is developed by García and Marín and consists of solving a sequence of simplified bilevel programs. In order to highlight the characteristics of the two methods a set of test problems have been solved in conjunction with other well known methods, such as the method of Spiess, the method of Chan, the method of Yang as well as with an adaptation of the Wolfe’s conjugate directions method for non-differentiable optimization, in order to provide a better perspective of their advantages and tradeoffs.     

On minimum congestion routing in rearrangeable multihop lightwave networks

In this article we consider the problem of minimizing the congestion in logically rearrangeable multihop lightwave networks. Namely, we consider a network in which each node is equipped with a small number of transmitters and receivers, and tuning a transmitter at nodei and a receiver at nodej to the same wavelength creates a logical link (i, j) through which traffic could be sent. For a given traffic matrix-the matrix of flows between nodes—the objective is to find the best connectivity diagram and the corresponding flow assignment so that the maximal flow on any link is minimized. We develop a tabu search heuristic that yields a suboptimal connectivity diagram and an optimal flow assignment on it. Computational experiments are conducted on some benchmark data sets, on a real-world traffic matrix, and on some randomly generated problems of larger dimension. The results are compared with known results from the literature and with a known greedy approach. The results suggest that a tabu search—based heuristic is a promising approach for handling this NP-hard combinatorial problem. In addition, we discuss the performance of the method in view of different patterns of input data.     

Motorway traffic parameter estimation from mobile phone counts

In this paper a new method for real time estimation of vehicular flows and densities on motorways is proposed. This method is based on fusing traffic counts with mobile phone counts. The procedure used for the estimation of traffic flow parameters is based on the hypothesis that “instrumented” vehicles can be counted on specific motorway sections and traffic flow can be measured on entrance and exit ramps. The motorway is subdivided into cells, assuming that mobile phones entering and exiting every cell can be counted during the observation period. An estimate of “instrumented” vehicle concentration is obtained and propagated on the network in time and space. This allows one to estimate traffic flow parameters by sampling “instrumented” traffic flow parameters using a “concentration” (the ratio of the densities of instrumented vehicles to the density of overall traffic) propagation mechanism.     

Sensitivity Analysis Based Method for Optimal Road Network Pricing

Road pricing is an important economic measure for optimal management of transportation networks. The optimization objectives can be the total travel time or total cost incurred by all the travelers, or some other environmental objective such as minimum emission of dioxide, an so on. Suppose a certain toll is posed on some link on the network, this will give an impact on flows over the whole network and brings about a new equilibrium state. An equilibrium state is a state of traffic network at which no traveler could decrease the perceived travel cost by unilaterally changing the route. The aim of the toll setting is to achieve such an equilibrium state that a certain objective function is optimized. The problem can be formulated as a mathematical program with equilibrium constraints (MPEC). A key step for solving such a MPEC problem is the sensitivity analysis of traffic flows with respect to the change of link characteristics such as the toll prices. In this paper a sensitivity analysis based method is proposed for solving optimal road pricing problems.     

Calculation of traffic flow breakdown probability to optimize link throughput

Traffic breakdown phenomenon is prevalent in empirical traffic system observations. Traffic flow breakdown is usually defined as an amount of sudden drop in traffic flow speed when traffic demand exceeds capacity. Modeling and calculating traffic flow breakdown probability remains an important issue when analyzing the stability and reliability of transportation system. The breakdown mechanism is still mysterious to practitioners and researchers in varying manner. Treating breakdown as a random event, this paper use discrete time Markov chain (DTMC) to model traffic state transition path, as a result, a transition probability matrix can be generated from empirical observations. From empirical analysis of breakdown, we found this formulation of breakdown probability follows the Zipf distribution. Therefore, a connection from traffic flow breakdown probability to how many vehicles are occupying a certain freeway segment (e.g. a link) will be established. Following from the results, a quantitative measure of breakdown probability can be obtained to optimize ramp metering rates to achieve optimum system performance measures.