Subjective-utility travel time budget modeling in the stochastic traffic network assignment

ABSTRACT

In this article, we propose a new model called subjective-utility travel time budget (SU-TTB) model to capture travelers' risk-averse route choices. In the travel time budget (TTB) and mean-excess travel time (METT) model, a predefined confidence level is needed to capture the risk-aversion in route choice. Due to the day-to-day route travel time variations, the exact confidence level is hard to be predicted. With the SU-TTB model, we assume travelers' confidence level belongs to an interval that they may comply with in the route choice. The two main components of SU-TTB are the utility function and the TTB model. We can show that the SU-TTB can be reduced to the TTB and METT model with proper utility function for the confidence levels. We can also prove its equivalence with our recently proposed nonlinear-expectation route travel time (NERTT) model in some cases and give some new interpretation on the NERTT with this equivalence. Finally, we formulate the SU-TTB model as a variational inequality (VI) problem to model the risk-averse user equilibrium (RAUE), termed as generalized RAUE (GRAUE). The GRAUE is solved via a heuristic gradient projection algorithm, and the model and solution algorithm are demonstrated with the Braess's traffic network and the Nguyen and Dupuis's traffic network.     

Effectiveness of travel time reliability indicators in the light of the assessment of dynamic managed lane strategy

ABSTRACT

The aim of traffic management is to ensure a high quality of service for a maximum number of users by decreasing congestion and increasing safety. Uncertainty of travel times decreases the quality of service and leads end users to modify their plans regardless of the average travel time. Indicators describing travel time reliability are being developed and should be used in the future both for the optimization and for the assessment of active traffic management operations. This article discusses the efficiency of certain reliability indicators in an ex-post assessment of a traffic management strategy. Ex-post assessment is based on an observational before–after study. As some factors other than the studied management strategy may intervene between the two periods, and as most reliability indicators require knowledge of the full travel time distribution and not only its average, a methodology is developed for the identification of the impact of these exogenous factors on the whole distribution. Many reliability indicators are split into different parts allowing the identification of the part due to the management strategy impact. The methodology is tested numerically on a managed lane operation consisting of Hard Shoulder Running (HSR) at rush hour on a section of a French motorway. The variation of some reliability indicators appears misleading, whereas the splitting of the indicators increases our understanding of the strategy and highlights its impact. The paper gives the reliability assessment of the HSR field test and discusses different reliability indicators to identify their potential performances and shortcomings.     

Robust traffic assignment model: Formulation,solution algorithms and empirical application

ABSTRACT

The deterministic traffic assignment problem based on Wardrop's first criterion of traffic network utilization has been widely studied in the literature. However, the assumption of deterministic travel times in these models is restrictive, given the large degree of uncertainty prevalent in urban transportation networks. In this context, this paper proposes a robust traffic assignment model that generalizes Wardrop's principle of traffic network equilibrium to networks with stochastic and correlated link travel times and incorporates the aversion of commuters to unreliable routes.

The user response to travel time uncertainty is modeled using the robust cost (RC) measure (defined as a weighted combination of the mean and standard deviation of path travel time) and the corresponding robust user equilibrium (UE) conditions are defined. The robust traffic assignment problem (RTAP) is subsequently formulated as a Variational Inequality problem. To solve the RTAP, a Gradient Projection algorithm is proposed, which involves solving a series of minimum RC path sub-problems that are theoretically and practically harder than deterministic shortest path problems. In addition, an origin-based heuristic is proposed to enhance computational performance on large networks. Numerical experiments examine the computational performance and convergence characteristics of the exact algorithm and establish the accuracy and efficiency of the origin-based heuristic on various real-world networks. Finally, the proposed RTA model is applied to the Chennai road network using empirical data, and its benefits as a normative benchmark are quantified through comparisons against the standard UE and System Optimum (SO) models.     

城市灯控平面交叉口的自行车交通设计研究

城市灯控平面交叉口混合交通流安全和效率的核心研究对象应该是自行车与机动车交通流间的相互影响。本丈在大量的理论分析和实践的基础上,探讨时空分离法的自行车交通设计的基本原则和交通空间设计方法,即自行车右转弯专用车道设计、左转自行车二次过街以及自行车与行人过街一体化设计,并进行了南京市太平北路与珠江路交叉口的应用实例分析。本文的城市灯控平面交叉口自行车的交通设计方法可为解决城市灯控平面交叉口混合交通问题提供借鉴。     

基于FDS公路隧道火灾仿真研究

针对公路隧道突发火灾事故问题,采用模拟软件对隧道发生的火灾进行研究。分析火灾条件下公路隧道内被困人群的疏散行为特点,给出隧道内人员疏散的安全依据,按照隧道火灾条件下通风风速不同时火灾烟气蔓延情况,确定火灾可利用疏散时间(ASET),通过分析人员疏散特点计算出所需的疏散时间(RSET),通过对比得出:通风风速至少为3m/s时才能保证人员的安全疏散。     

�����ν���Э���ĵ�������վ�򳵿����Ż�

研究了高峰时段列车运行的衔接协调对换乘站候车客流量的优化问题。首先分析了换乘站各站台候车客流的组成因素,确定出各运行方向的换乘站台内客流量随时间变化的规律。然后,以时段内换乘站候车客流量的最大值最小为目标,建立优化模型。模型以站台最大可容纳候车人数为约束条件,以各方向列车在换乘站的到达时刻为调整对象,实现了高峰时段换乘站内聚集客流的优化。最后,针对验证案例,设计了遗传算法进行求解,得出了协调较优解,并给出与较劣解的对比分析。结果表明,该优化方法能够有效降低换乘站内的候车客流人数,可为网络化的优化协调工作提供参考。     

基于时间约束的铁路空车调配系统可靠性分析

为弥补现有铁路空车调配系统缺乏空车调配可靠性研究的缺陷,在传统空车调配优化模型的基础上,本文提出了一种新的基于时间约束的空车调配可靠性分析方法。通过深入分析铁路空车调配过程,建立效益最大化目标函数,生成约束条件,以规定时间内的实际到达空车数与需求空车数之比计算出各需求站的空车调配可靠性,再利用各需求站可靠性均值求解空车调配系统的可靠性。最后,使用LINGO软件进行算例分析,论证了该方法的可行性和有效性。     

考虑多人相互影响的舰船通道最短路径规划

将时间维引入既定舰船通道网络,把考虑多人相互影响的动态最优路径规划问题转化为时间依赖网络中的最优路径搜索问题。首先,论文的算法为所有人员随机生成走行路径,为了预测网络中的弧(路段)的走行时间,按人员速度从慢到快的顺序依次计算并记录人员到达路径中的各路段首节点的时刻,先记录到的人员将成为后记录到的人员的动态障碍。然后,将遗传算法与网络中弧的走行时间预测方法相结合,借助遗传算法的个体多样性天然地解决了人员走行任意性问题,因而获得了全局动态最优路径算法,并仿真计算了两人以及三人的最短时间路径;经与不考虑人员间相互影响时获得的最优路径相比较,论文的算法获得了人员遇到障碍时(或跟行或绕行)的最优走行路径。最后,借助时间依赖网络中的最优路径充要条件定理,说明了算法的有效性。     

响应谱法与时程法在管道水锤分析中的对比研究

水锤是输流管道中经常发生的现象,由于阀门操作不当或设备突然停车引起的水锤极易引起管道的振动,造成设备及支架的破坏,严重影响管道系统的正常运行。文章运用CAESAERⅡ软件,对管道中的水锤现象分别采用响应谱法和时程分析法进行分析。结果表明:响应谱法有利于对振动响应过大模态的精确控制,时程法能精确求解时间历程内各时刻系统的整体响应。为全面分析水锤对管道应力的影响提供了一个研究思路。     

集装箱装卸设备采购项目管理中的约束条件和质量管理

以集装箱装卸设备采购工作为例,探讨项目管理中的约束条件(范围、费用、时间)与质量管理之间的关系,分析它们之间的相互作用和影响.