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动态交通分配的特性在脱线交通网络设计、政策评估、和在线运作及管理中有重要的含义.虽然动态交通分配的研究仍然是十分活跃，可是其特性及其含义在以往的文献中并没有完全地受到注意或重视.现在是来总结我们在动态交通分配研究中所学的知识和研究方向适当的时候.本文回顾了动态交通分配公式化的方法、比较其利用不同交通流量模型时的特性、谈论其含义和提出一些未来研究发展的新方向.     

城市道路最大出行距离计算模型

为了合理体现交通事故延误对出行者路径选择的影响, 提出了随机状态下的交通事故时间延误模型。将交通事故的随机性、持续时间和道路通行能力等不确定性因素引入到交通分配模型中, 并对路径选择模型进行修正。分析了各等级道路最大适宜出行范围, 根据修正的路径选择模型, 采用逐次交通分配方法, 得到各等级道路的出行周转量和出行距离, 并与不考虑交通事故延误时的出行距离进行了对比分析。分析结果表明: 当考虑交通事故延误时, 支路、次干路、主干路、快速路的最大出行距离分别为2.000、2.946、4.054、5.963 km; 当不考虑交通事故延误时, 支路、次干路、主干路、快速路的最大出行距离分别为2.000、3.000、6.000、10.000 km; 交通事故延误是影响出行者路径选择的重要因素; 当考虑交通事故延误时, 高等级道路的最大出行距离变小。相比于传统的路径选择模型, 本文模型更优。     

Modelling public transport on‐board congestion: comparing schedule‐based and agent‐based assignment approaches and their implications

Transit systems are subject to congestion that influences system performance and level of service. The evaluation of measures to relieve congestion requires models that can capture their network effects and passengers' adaptation. In particular, on‐board congestion leads to an increase of crowding discomfort and denied boarding and a decrease in service reliability. This study performs a systematic comparison of alternative approaches to modelling on‐board congestion in transit networks. In particular, the congestion‐related functionalities of a schedule‐based model and an agent‐based transit assignment model are investigated, by comparing VISUM and BusMezzo, respectively. The theoretical background, modelling principles and implementation details of the alternative models are examined and demonstrated by testing various operational scenarios for an example network. The results suggest that differences in modelling passenger arrival process, choice‐set generation and route choice model yield systematically different passenger loads. The schedule‐based model is insensitive to a uniform increase in demand or decrease in capacity when caused by either vehicle capacity or service frequency reduction. In contrast, nominal travel times increase in the agent‐based model as demand increases or capacity decreases. The marginal increase in travel time increases as the network becomes more saturated. Whilst none of the existing models capture the full range of congestion effects and related behavioural responses, existing models can support different planning decisions. Copyright © 2016 John Wiley & Sons, Ltd.     

Route swapping in dynamic traffic networks

A dynamic traffic assignment (DTA) model typically consists of a traffic performance model and a route choice model. The traffic performance model describes how traffic propagates (over time) along routes connecting origin-destination (OD) pairs, examples being the cell transmission model, the vertical queueing model and the travel time model. This is implemented in a dynamic network loading (DNL) algorithm, which uses the given route inflows to compute the link inflows (and hence link costs), which are then used to compute the route travel times (and hence route costs). A route swap process specifies the route inflows for tomorrow (at the next iteration) based on the route inflows today (at the current iteration). A dynamic user equilibrium (DUE), where each traveller on the network cannot reduce his or her cost of travel by switching to another route, can be sought by iterating between the DNL algorithm and the route swap process. The route swap process itself takes up very little computational time (although route set generation can be very computationally intensive for large networks). However, the choice of route swap process dramatically affects convergence and the speed of convergence. The paper details several route swap processes and considers whether they lead to a convergent system, assuming that the route cost vector is a monotone function of the route inflow vector.     

A competitive, charter air-service planning model for student athlete travel

This paper presents a model for planning an air charter service for pre-scheduled group travel. This model is used to investigate the competitiveness of such an enterprise for student athlete travel in conference sports. The relevant demand subset to be served by a limited charter fleet is identified through a comparison with existing scheduled travel options. Further, the routing and scheduling of the charter aircraft is performed within the same framework. Through this modeling a method for formulating and accommodating continuous time windows and competitive market dynamics in strategic planning for a charter service is developed. Computational improvements to the basic model are also presented and tested. The model is applied to the Big Sky Conference for the 2006-2007 season, quantifying the benefits to the students from such a service and the change in expenditure associated with such a benefit for various assumptions about operations and value of time. The findings indicate the lack of spatial or sport based patterns for maximizing benefit, indicating the absence of simplistic “rules of thumb” for operating such a service, and validating the need for the model.     

Deficiencies in accident record systems

As part of the continuous process of improving highway safety, the engineer relies heavily on information provided by accident record systems. The study described in this paper sought to determine the reliability of this system in New Mexico. Techniques employed in the study included internal consistency checks, comparison with other record systems, and matching actual and reported crash site data. The extent of omitted and inaccurate data having primary relevance to engineering analyses was found to exceed acceptable limits. Incorrect locational information was the most serious problem. The recommended solutions to this problem consist of a modified accident report form and improved contact with enforcement officials.     

ATIS 作用下弹性需求混合交通均衡的效率损失

在ATIS 用户和利己用户组成的交通网络中,利己用户遵循用户均衡原则选择出行路径,其目的是最小化自身出行成本;先进出行者信息系统(ATIS)用户遵循系统最优原则选择出行路径,其目的是最小化系统总出行成本. 本文基于ATIS 用户和利己用户路径选择原则的异质性,对弹性需求下该类混合交通均衡分配的效率损失进行探讨. 构建弹性需求下该类混合交通均衡分配的变分不等式模型,界定其效率损失上界. 结果表明,效率损失上界与用户均衡时社会总收益与社会总剩余之比相关,还与用户均衡时路段上ATIS 用户的流量与总流量之比有关.     

考虑个体驾驶速度偏差的车辆调度模型

考虑驾驶速度偏差, 建立了多驾驶人、多种车型、多种物资、多仓库点和多需求点的物资车辆调度模型, 分别以整体运输时间最短、整体运输成本最低以及综合整体运输时间与成本最小为目标, 研究了个体驾驶速度偏差对上述目标的影响; 将驾驶人参数加入到遗传算法的基因编码中, 建立了驾驶人唯一性约束、初始地点约束以及物资供需数量约束, 保证每个基因个体中驾驶人分配方案可行, 且物资运输不超供需总量; 采用遗传算法求解了随机分配驾驶人条件下有驾驶速度偏差与无驾驶速度偏差时各目标的车辆调度方案。计算结果表明: 优化调度方案满足模型中的所有约束条件; 3种目标下的最优方案中, 驾驶人的分配方案不同, 说明目标函数受驾驶人驾驶速度偏差影响; 有驾驶速度偏差情况下的各目标调度结果均优于相应无驾驶速度偏差的调度结果, 3种目标函数差比分别为3.50%、2.96%和1.13%, 说明驾驶速度偏差对求解质量有一定影响; 驾驶人随机分配时的各目标调度结果均劣于相应最优结果, 3种目标函数差比分别为3.91%、2.47%和1.98%, 说明驾驶速度偏差会影响调度效率, 优化驾驶人分配方案能降低整体运输时间与成本。由此可见, 根据特定的调度目标对驾驶人进行合理分配, 可以得到更符合调度目标、更贴近实际、更经济省时的车辆调度方案。     

基于路网容量的城市中心商业区停车设施供给研究

本文利用双层规划模型从城市动态变通和静态交通的相互约束关系出发,以城市道路网动态交通容量及服务水平为约束条件,预测城市中心商业区可以容纳的最大停车泊位数量,在双层模型中,上层模型以城市中心商业区的停车泊位数量最大为目标,约束条件是城市道路网路段上动态变通流量不超过相应的容量;下层模型是普通的用户平衡分配问题,用来优化用户出行的路线选择行为。文章的最后,应用该双层模型具体研究了大连市的中心商业区的停车泊位数量。