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.     

Stabilization of traffic flow in optimal velocity model via delayed-feedback control

Traffic jams may occur due to various reasons, such as traffic accidents, lane reductions and on-ramps. In order to suppress the traffic congestion in an optimal velocity traffic model without any driver’s delay taken into account, a delayed-feedback control of both displacement and velocity differences is proposed in this study. By using the delay-independent stability criteria and the H_∞-norm, the delayed-feedback control can be determined to stabilize the unstable traffic flow and suppress the traffic jam. The numerical case studies are given to demonstrate and verify the new control method. Furthermore, a comparison is made between the new control method and the method proposed by Konishi et al. [K. Konishi, M. Hirai, H. Kokame, Decentralized delayed-feedback control of an optimal velocity traffic model, Eur. Phys. J. B 15 (2000) 715–722]. The results show that the new control method makes the traffic flow more stable and improves the control performance.     

Using intelligent agents for pro-active,real-time urban intersection control

The usability and effectiveness of traffic control systems greatly depends on its ability of reacting upon traffic patterns and permutations. In this research we investigate the applicability of autonomous intelligent agents in Urban Traffic Control (UTC), and why these artificial intelligent strategies are useful in UTC. We propose a system that autonomously can adapt itself, based upon internal rules and its environment, at changing environments. Both long term changes as well as short term changes are accounted for in different manner. The UTC model is primarily based on several Intelligent Traffic Signalling Agents (ITSA) and some authority agents. This approach enables us to use a UTC system, based on agent technology, capable of responding to traffic conditions in real-time. The system can maintain its integrity and stability within the overall transportation system. Due to its pro-active behaviour we are able to make better use of the capacity of intersections.     

Differential transform method for mathematical modeling of jamming transition problem in traffic congestion flow

In this paper we aim to find an analytical solution for jamming transition in traffic flow. Generally the Jamming Transition Problem (JTP) can be modeled via Lorentz system. So, in this way, the governing differential equation achieved is modeled in the form of a nonlinear damped oscillator. In current research the authors utilized the Differential Transformation Method (DTM) for solving the nonlinear problem and compared the analytical results with those ones obtained by the 4th order Runge-Kutta Method (RK4) as a numerical method. Further illustration embedded in this paper shows the ability of DTM in solving nonlinear problems when a so accurate solution is required.     

Analysis of a modified two-lane lattice model by considering the density difference effect

In this paper, a modified lattice hydrodynamic model of traffic flow is proposed by considering the density difference between leading and following lattice for two-lane system. The effect of density difference on the stability of traffic flow is examined through linear stability analysis and shown that the density difference term can significantly enlarge the stability region on the phase diagram. To describe the phase transition of traffic flow, the Burgers equation and mKdV equation near the critical point are derived through nonlinear analysis. To verify the theoretical findings, numerical simulation is conducted which confirms that traffic jam can be suppressed efficiently by considering the density difference effect in the modified lattice model for two-lane traffic.     

Multi-service multi-facility network design under uncertainty

The problem of designing high speed networks using different modules of link capacities, in the same model, in order to meet uncertain demands obtained from different probability distribution functions (PDF) is a very hard and challenging real network design problem. The novelty of the new model, compared to previous ones, is to allow installing more than one module per link having equal or different capacities. Moreover, the scenarios of traffic can be generated, according to practical observations, from the main classes of uncertain demands (multi-service) simulated from different PDFs, including heavy tailed ones. These classes of traffic are considered simultaneously for the scenario generation, different from related works in the literature that use only one probability distribution function to simulate the scenarios of traffic. In this work we present the problem formulation and report computational results using branch-and-bound and L-shaped decomposition solution approaches. We consider in the same model up to three different types of modular capacities (multi-facility), since it seems that using more than this can lead to an intractable model. The objective is to minimize penalty (in case of unmet demands) and investment costs. We obtain confidence intervals (with 95% of covering rate) on the expected optimal solution value for the resulting two-stage stochastic integer-modular problem and discuss when they are meaningful. Numerical experiments show that our model can handle up to medium real size instances.     

超音速平板边界层转捩中层流突变为湍流的机理研究

采用空间模式,对来流Mach数为4.5的平板边界层转捩过程做了直接数值模拟．对结果进行的分析发现,在层流-湍流转捩的突变(breakdown)过程中,层流剖面得以快速转变为湍流剖面的机理在于平均剖面的修正导致了其稳定性特征的显著变化．虽然在层流下第2模态T-S波更不稳定,但在层流突变为湍流的过程中,第1模态不稳定波也起了重要作用．     

Model of traffic flow and blocking probability analysis of an m-asymmetrical two stage incomplete link system

In the first part of this study we present and review a simplified model for the traffic flow between the switches of a modular switching system. In the second part, an approximated model for calculating the blocking probability on a system with this type of architecture is presented and then generalized to a structure here defined as an m-asymmetrical incomplete link system. The model is based on the probabilistic hypothesis of Jacobaeus and leads to a system of formulae which may be calculated using a computing language allowing for recursive subprograms.     

Correlated Brownian Motions as an Approximation to Deterministic Mean-Field Dynamics

We analyze the transition from deterministic mean-field dynamics of several large particles and infinitely many small particles to a stochastic motion of the large particles. In this transition the small particles become the random medium for the large particles, and the motion of the large particles becomes stochastic. Under the assumption that the empirical velocity distribution of the small particles is governed by a probability density ψ, the mean-field force can be represented as the negative gradient of a scaled version of ψ. The stochastic motion is described by a system of stochastic ordinary differential equations driven by Gaussian space-time white noise and the mean-field force as a shift-invariant integral kernel. The scaling preserves a small parameter in the transition, the so-called correlation length. In this set-up, the separate motion of each particle is a classical Brownian motion (Wiener process), but the joint motion is correlated through the mean-field force and the noise. Therefore, it is not Gaussian. The motion of two particles is analyzed in detail and a diffusion equation is deduced for the difference in the positions of the two particles. The diffusion coefficient in the latter equation is spatially dependent, which allows us to determine regions of attraction and repulsion of the two particles by computing the probability fluxes. The result is consistent with observations in the applied sciences, namely that Brownian particles get attracted to one another if the distance between them is smaller than a critical small parameter. In our case, this parameter is shown to be proportional to the aforementioned correlation length. __________ Published in Ukrains'kyi Matematychnyi Zhurnal, Vol. 57, No. 6, pp. 757–769, June, 2005.     

Estimation of urban traffic conditions using an Automatic Vehicle Location (AVL) System

The aim of this paper is to develop an Information Extension Model (IEM) which uses location data of bus fleets (AVL data) to estimate road traffic conditions and provide input for implementing control strategies. The IEM consists of three sub-models: the Link Traffic Condition Model (LTCM), the AVL Adaptation Model (AVLAM) and the Network Traffic Condition Model (NTCM). The first provides road traffic conditions as a function of mass-transit traffic conditions in the case of shared lanes, the second provides mass-transit traffic conditions as a function of AVL data, and the last provides road traffic conditions over the whole road network as a function of mass-transit traffic conditions.     

Braess's Paradox in large random graphs

Braess's Paradox is the counterintuitive fact that removing edges from a network with “selfish routing” can decreasethe latency incurred by traffic in an equilibrium flow. We prove that Braess's Paradox is likely to occur in a natural random network model: with high probability, there is a traffic rate and a set of edges whose removal improves the latency of traffic in an equilibrium flow by a constant factor. © 2010 Wiley Periodicals, Inc. Random Struct. Alg., 2010     

Improving short-term conflict alert via tabu search

In this paper we describe some work carried out by National Air Traffic Services in the UK into developing optimisation tools to help improve the effectiveness of one of their air traffic control safety systems—short-term conflict alert. In short-term conflict alert a computer system continually monitors radar data and alerts air traffic controllers if it detects a situation where two aircraft are in danger of approaching too close to one other. Within the computer program that makes up the short-term conflict alert system is a large number of parameters. Choosing appropriate values for these parameters is a task that is currently done via extensive human intervention. In this paper we describe how a modern heuristic technique, tabu search, can be used to make parameter choices.     

主路多车道无信号交叉口混合交通流的通行能力

Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions,road conditions and so on.Highway construction and management is judged by capacity standard.The reasonable scale and time of highway construction,rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume.All over the world,highway capacity is studied to different extent in different country. Based on the gap acceptance theory,the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory.Capacity model of the minor mixed traffic flows crossing m major lanes,on which the traffic flows fix in with M3 distributed headway,on the unsignalized intersection is set up,and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.     

我国典型省份交通网络建设系统效用及关联分析

着眼于国家在2006年提出的中部地区建设综合交通运输枢纽的战略部署,结合我国在2008年进行大规模建设投资的背景,按照系统工程的观点,分析了区域交通建设投资对经济增长的拉动效应及关联性问题,试图探求我国典型省份在区域经济,财政等资源受限情况下交通网络建设投资的合理性及风险问题,并根据研究区域的实际情况提出压缩交通建设总规模,转变交通建设重点,大力发展城市公共交通等对策和建议,以期对提高交通建设投资效益提供参考.     

Sensitivity analysis for correlation-based registration of digital images

Traffic management systems, which derive their measurements of vehicle counts, class, speed, and occupancy from TV sensors, are growing in popularity. The advantage of such systems is that, as new lanes are defined, the information of detection zones can be reprogrammed without having to physically move any embedded sensors. However, such TV cameras are frequently used in the dual roles of a traffic monitor, and of a traffic surveillance sensor. In the latter role, the TV camera is often moved in some pan or tilt, and even zoom mode. Following such a use, the camera is returned to its traffic monitor role. For many systems, this return to the traffic monitor mode requires a manual realignment. For other systems, this alignment is automatic and based upon a straightforward use of correlation or a variant of a modified correlation scheme. The question the system designer is required to answer is that of how accurate is this realignment. The answer is a function of measurable image variables. What is presented below is the theoretical analysis of that correlation process. This analysis allows the designer to tradeoff the selection of the correlation process such that accuracy might be maintained in spite of changes in such variables as signal-to-background measurements, signal-to-noise, and average pixel-to-pixel correlation.     

北京市道路交通事故致死率的分析与预测

根据北京市道路交通事故的统计资料,以交通事故致死率为指标,对北京市目前道路交通安全情况进行评价.并基于灰色预测理论,建立北京市道路交通事故死亡人数的灰色GM(1,1)预测模型.预测结果显示,北京市未来几年道路交通事故死亡人数虽处于下降趋势,但死亡人数仍在千人左右,平均每起事故死亡人数仍处于上升趋势,道路交通事故致死率仍然偏高.道路交通管理部门应加大惩治道路交通违法行为力度,以控制道路交通事故的严重后果.     

Estimating summary functionals in multistate models with an application to hospital infection data

Inhomogeneous Markov chains are a relevant framework for analysing event histories. The fundamental estimator in the presence of incompletely observed data is the Nelson-Aalen estimator of the multivariate cumulative hazards. It may be summarised in terms of probability estimates via the empirical transition matrix. The empirical transition matrix has only slowly entered applications, one reason being previous lack of software. In a number of applications, further summary measures are desired. We illustrate how they may be computed from the empirical transition matrix and why bootstrapping their variance works. In contrast, computing such summaries outside the present framework has typically led to biased results. As an example, we consider in more detail hospital stay following infectious complication. This summary quantity is often considered by clinical decision makers, but reliable estimates require modelling the timing of infection as in the present set-up. In this context, we also derive new summary measures that further distinguish between patients discharged and patients deceased.     

A traffic shaping model for optimizing network operations

The management of technology in multi-service computer networks, such as university networks, has become a challenge with the explosive growth of entertainment oriented peer-to-peer (P2P) traffic. Traffic shaping is one of the tools used to manage bandwidth to improve system performance by allocating bandwidth between P2P and non-peer-to-peer (NP2P) traffic. We present a model for traffic shaping and bandwidth management that considers the trade-offs from allocating different amounts of bandwidths for different application categories and use data from a university network. The current policy allocates varying bandwidths over the day to P2P and NP2P traffic to reflect the importance of not letting entertainment based traffic choke the network during the day time at the expense of the more important traffic, such as Web traffic. We highlight the difficulties in obtaining data in the form required for analysis, and the need to estimate demand for allocations not covered by current policy. We present a goal programming model for this estimation task. We also model the traffic shaping problem as a Markov decision process and develop an algorithm for determining the optimal bandwidth allocation to maximize the utility of all users. Finally we use a numerical example to illustrate our approach.     

某型人工台断话问题建模分析及应用

该文利用排队论建立概率模型,估计出了由于设备软件设计缺陷造成断话的概率,并确定了软件设计缺陷是造成系统断话的主要原因。经采取相应措施后断话率大幅降低(经计算至少减少39.6%),提高了通信网的可靠性和稳定性,是利用概率统计方法分析解决通信网系运行故障的有效尝试。     

突发交通事件非参数诊断的变点统计方法研究

针对智能运输系统(ITS)项目特别是先进的出行信息系统的开发，建立了突发交通事件非线性非参数诊断的变点统计方法。依据交通流理论，结合均值变点模型，对变点搜索的最小二乘法和局部比较法进行了研究。利用在英国南安普敦市检获的实际数据对上述两种算法进行了标定，并对模型进行实际应用。结果显示上述方法对突发事件检测具有很高的灵敏度和有效性。