基于元胞自动机的高速铁路列车群追踪运行仿真模型

为分析高速铁路列车在追踪间隔缩小时的运行状态,根据准移动闭塞系统原理,设置列车区间运行和车站运行的演化规则,建立准移动闭塞条件下基于元胞自动机的列车群追踪运行仿真模型。利用元胞自动机对京沪高速铁路线路"上海虹桥—南京南"运行图中追踪运行的10列车进行建模仿真,分析仿真结果验证到达间隔时间是制约追踪间隔的瓶颈,并得出后行列车满足追踪间隔4 min或3 min的情况下,其运行速度不受前行列车的干扰。     

An improved cellular automaton with axis information for microscopic traffic simulation

Cellular Automaton (CA), an efficient dynamic modeling method that is widely used in traffic engineering, is newly introduced for traffic load modeling. This modeling method significantly addresses the modest traffic loads for long-span bridges. It does, however, require improvement to calculate precise load effects. This paper proposed an improved cellular automaton with axis information, defined as the Multi-axle Single-cell Cellular Automaton (MSCA), for the precise micro-simulation of random traffic loads on bridges. Four main ingredients of lattice, cells’ states, neighborhoods and transition rules are redefined in MSCA to generate microscopic vehicle sequences with detailed vehicle axle positions, user-defined cell sizes and time steps. The simulation methodology of MSCA is then proposed. Finally, MSCA is carefully calibrated and validated using site-specific WIM data. The results indicate: (1) the relative errors (REs) for the traffic parameters, such as volumes, speeds, weights, and headways, from MSCA are basically no more than ±10% of those of WIM data; (2) the load effects of three typical influence lines (ILs) with varied lengths of 50, 200 and 1000 m are also confidently comparable, both of which validate the rationality and precision of MSCA. Furthermore, the accurate vehicle parameters and gaps generated from MSCA can be applied not only for precise traffic loading on infrastructures but also for the accurate estimation of vehicle dynamics and safety. Hence, wide application of MSCA can potentially be expected.     

基于PFV策略的连续型元胞自动机交通流模型

科学合理的微观交通流仿真模型是研究交通控制手段有效性的关键.本文结合一种考虑驾驶员视野内前后多车影响的跟驰策略，建立了连续型元胞自动机交通流模型.仿真实验表明，仿真数据与实测数据有较好的拟合性，仿真得到的 K-Q、K-V和 Q-V图能较好地反映实际道路交通流的失稳现象，所建立的模型具有适应不同场景的兼容性与灵活性，能够作为研究我国实际道路交通流问题的仿真工具.     

Influence of priority taking and abstaining at single-lane roundabouts using cellular automata

Existing roundabout simulation models fail to consider all types of driver behavior which compromises their accuracy and ability to accurately evaluate roundabout performance. Further, these non-compliant driver behaviors, including priority taking and priority abstaining, are inconsistent with existing traffic flow theories. In this paper, a new cellular automata model, C.A.Rsim, is developed and calibrated with field data from five single-lane roundabouts in four northeastern states. Model results indicate that approximately 20% of the individuals in the driver population are inclined to priority taking and approximately 20% are inclined to priority abstaining behavior, though the observed levels of these types of behavior are naturally lower and vary with traffic volume. The model results also corroborate other research indicating that current models can overestimate capacity at higher circulating volumes, possibly a result of the jamming effect produced by priority taking behavior. The reduction in priority abstaining behavior, which is observed at older roundabouts, significantly reduces delay and queue length in certain traffic volumes. C.A.Rsim is also more parsimonious than many existing microsimulation models. These results provide insight on how variations in conflicting flow (i.e., traffic volume and turning movement balance) impact the amount of observed non-compliant behavior.     

Evaluation of a cellular phone-based system for measurements of traffic speeds and travel times: A case study from Israel

The purpose of this paper is to examine the performance of a new operational system for measuring traffic speeds and travel times which is based on information from a cellular phone service provider. Cellular measurements are compared with those obtained by dual magnetic loop detectors. The comparison uses data for a busy 14 km freeway with 10 interchanges, in both directions, during January–March of 2005. The dataset contains 1 284 587 valid loop detector speed measurements and 440 331 valid measurements from the cellular system, each measurement referring to a 5 min interval. During one week in this period, 25 floating car measurements were conducted as additional comparison observations. The analyses include visual, graphical, and statistical techniques; focusing in particular on comparisons of speed patterns in the time–space domain. The main finding is that there is a good match between the two measurement methods, indicating that the cellular phone-based system can be useful for various practical applications such as advanced traveler information systems and evaluating system performance for modeling and planning.     

无灯控行人过街元胞自动机交通模型研究

以无灯控行人过街对交通流影响为分析目标,在综合考虑行人穿越行为及车辆行为的基础上,建立了相应的行人及车辆元胞自动机模型规则,尤其是在模型中提出了行人等待区的概念及基于等待区内有无行人的车辆行为规则。以上述模型为基础,通过对不同行人产生概率及速度快的行人比例情况时路段交通流演化趋势进行了仿真。     

Cellpath: Fusion of cellular and traffic sensor data for route flow estimation via convex optimization

A new convex optimization framework is developed for the route flow estimation problem from the fusion of vehicle count and cellular network data. The issue of highly underdetermined link flow based methods in transportation networks is investigated, then solved using the proposed concept of cellpaths for cellular network data. With this data-driven approach, our proposed approach is versatile: it is compatible with other data sources, and it is model agnostic and thus compatible with user equilibrium, system-optimum, Stackelberg concepts, and other models. Using a dimensionality reduction scheme, we design a projected gradient algorithm suitable for the proposed route flow estimation problem. The algorithm solves a block isotonic regression problem in the projection step in linear time. The accuracy, computational efficiency, and versatility of the proposed approach are validated on the I-210 corridor near Los Angeles, where we achieve 90% route flow accuracy with 1033 traffic sensors and 1000 cellular towers covering a large network of highways and arterials with more than 20,000 links. In contrast to long-term land use planning applications, we demonstrate the first system to our knowledge that can produce route-level flow estimates suitable for short time horizon prediction and control applications in traffic management. Our system is open source and available for validation and extension.     

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在Nege1．Schreken berg单车道元胞自动机交通流模型的基础上，考虑面向高速公路的一维交通流运行状况，细化格点并进行计算机仿真。观测车辆的运行情况，并对车辆的平均速度和延误加以研究。仿真结果表明，车辆平均速度和延误符合它们的基本变化趋势。从仿真结果生成的时空图上我们可以看出，本文模型所生成的时空图所出现的阻塞相要比NS模型所出现的阻塞相平缓。且由于我们在仿真过程中使车辆加速度降低到合理的大小，让车辆的运行过程更加连续，因此本文模型比NS模型更加贴近现实。     

基于元胞自动机的交通流状态研究

为方便交通部门能够更直接地掌握道路交通流状态,对交通流进行管理、调节和诱导,从而提高路网交通效率,本文主要围绕交通流状态统计、交通流状态仿真和不同交通状态的决策方案三个方面进行研究。研究基于物理公式和格林希尔治模型理论构建交通流流量与车辆平均速度的基础模型,根据不同道路的最大流量判断道路交通状态;利用matlab将道路简化为元胞自动机的运动过程进行分析;并根据交通流状态分析结果提出合理的决策方案。     

基于时间自动机模型的安全计算机平台的形式化验证

众多工业控制领域要求计算机控制系统具有高可靠、高可用和高安全的运行基础,2乘2取2冗余结构的安全计算机平台是提高系统安全性、可靠性的一种重要解决方式。CBTC列控系统的安全计算机平台采用2乘2取2冗余结构,它是一个实时系统,控制过程需要考虑时间因素。本文分析CBTC系统安全计算机平台系统的组成结构,提取出系统的功能约束,采用基于时间自动机理论的建模验证工具UPPAAL建立系统的自动机网络模型,进行仿真分析,验证系统的功能性、实时性、安全性要求。