微观交通仿真中的行人干扰模型

中国的城市交通以非机动车和机动车的混合交通流为主,行人干扰现象严重。行人干扰模型是城市微观交通仿真模型的重要组成部分。经过现场调查及分析行人对交通干扰的概率分布,提出行人干扰模型。根据实际测量情况,确定其概率函数,给出各参数的含义,参数可修正以适应不同的交通状况,最后给出计算机实现算法。     

对永嘉乌龙坑大桥倒塌的思考

结合工程实例,分析了永嘉乌龙坑大桥倒塌的原因,并从管理角度对我国民间桥梁建设中存在的问题进行了探讨,提出了具体措施。     

Traffic evacuation simulation based on multi-level driving decision model

Traffic evacuation is a critical task in disaster management. Planning its evacuation in advance requires taking many factors into consideration such as the destination shelter locations and numbers, the number of vehicles to clear, the traffic congestions as well as traffic road configurations. A traffic evacuation simulation tool can provide the emergency managers with the flexibility of exploring various scenarios for identifying more accurate model to plan their evacuation. This paper presents a traffic evacuation simulation system based on integrated multi-level driving-decision models which generate agents’ behavior in a unified framework. In this framework, each agent undergoes a Strategic, Cognitive, Tactical and Operational (SCTO) decision process, in order to make a driving decision. An agent’s actions are determined by a combination, on each process level, of various existing behavior models widely used in different driving simulation models. A wide spectrum of variability in each agent’s decision and driving behaviors, such as in pre-evacuation activities, in choice of route, and in the following or overtaking the car ahead, are represented in the SCTO decision process models to simulate various scenarios. We present the formal model for the agent and the multi-level decision models. A prototype simulation system that reflects the multi-level driving-decision process modeling is developed and implemented. Our SCTO framework is validated by comparing with MATSim tool, and the experimental results of evacuation simulation models are compared with the existing evacuation plan for densely populated Beijing, China in terms of various performance metrics. Our simulation system shows promising results to support emergency managers in designing and evaluating more realistic traffic evacuation plans with multi-level agent’s decision models that reflect different levels of individual variability of handling stress situations. The flexible combination of existing behavior and decision models can help generating the best evacuation plan to manage each crisis with unique characteristics, rather than resorting to a fixed evacuation plan.     

Evacuation traffic dynamics

Historically, evacuation models have relied on values of road capacity that are estimated based on Highway Capacity Manual methods or those observed during routine non-emergency conditions. The critical assumption in these models is that capacity values and traffic dynamics do not differ between emergency and non-emergency conditions. This study utilized data collected during Hurricanes Ivan (2004), Katrina (2005) and Gustav (2008) to compare traffic characteristics during mass evacuations with those observed during routine non-emergency operations. From these comparisons it was found that there exists a consistent and fundamental difference between traffic dynamics under evacuation conditions and those under routine non-emergency periods. Based on the analysis, two quantities are introduced: “maximum evacuation flow rates” (MEFR) and “maximum sustainable evacuation flow rates” (MSEFR). Based on observation, the flow rates during evacuations were found to reach a maximum value of MEFR followed by a drop in flow rate to a MSEFR that was able to be sustained over several hours, or until demand dropped below that necessary to completely saturate the section. It is suggested that MEFR represents the true measure of the “capacity”. These findings are important to a number of key policy-shaping factors that are critical to evacuation planning. Most important among these is the strong suggestion of policy changes that would shift away from the use of traditional capacity estimation techniques and toward values based on direct observation of traffic under evacuation conditions.     

Variable guidance for pedestrian evacuation considering congestion,hazard, and compliance behavior

A methodology for optimizing variable pedestrian evacuation guidance in buildings with convex polygonal interior spaces is proposed. The optimization of variable guidance is a bi-level problem. The calculation of variable guidance based on the prediction of congestion and hazards is the upper-level problem. The prediction of congestion provided the variable guidance is the lower-level problem. A local search procedure is developed to solve the problem. The proposed methodology has three major contributions. First, a logistic regression model for guidance compliance behavior is calibrated using a virtual reality experiment and the critical factors for the behavior are identified. Second, the guidance compliance and following behaviors are considered in the lower-level problem. Third, benchmarks are calculated to evaluate the performance of optimized variable guidance, including the lower bound of the maximum evacuation time and the maximum evacuation time under a fixed guidance. Finally, the proposed methodology is validated with numerical examples. Results show that the method has the potential to reduce evacuation time in emergencies.     

步行和自行车交通系统层次化网络构建方法--以海南省三亚市为例

针对步行和自行车交通网络规划缺乏系统方法的情况,以《城市步行和自行车交通系统规划设计导则》编制研究为基础,从使用者意愿角度出发,提出以步行和自行车交通分区、步行和自行车道路分级为核心的层次化网络构建方法。采用定性与定量相结合的方法划定分区,以契合政策导向和设施供给的双重属性;根据步行和自行车出行特点差异,提出契合城市空间结构和用地布局的差异化布局模式;给出步行和自行车道密度、宽度指标,以及在空间、环境、衔接层面的设计指引。强调在相关规划中落实控制指标,以保障步行和自行车交通系统层次化网络的构建。     

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针对疏散过程中交叉口易造成延误的问题,构建了基于消除交叉冲突的疏散网络优化双层模型,上层以总疏散时间最短为目标,对各车道转向进行最优设置,下层基于随机用户平衡原理进行路径选择,并运用遗传算法与逐次平均算法结合对该模型进行求解,最终实现疏散交通组织与路径规划的集成优化.本文基于简单实验对模型的收敛性与有效性进行校验,实验表明,运用本文所提出的模型能够有效求解消除交叉冲突下的疏散网络优化问题,且算法的收敛速度较快;基于实际案例证明,本文提出的疏散网络优化模型能通过对交叉口处部分转向的禁行,消除交叉冲突,避免其余转向交通流的中断,从而提高疏散效率.     

考虑行人随机行为波动的改进社会力模型

为在仿真模型中更全面地反映行人特性,并研究随机行为对双向行人过街的影响,本文基于社会力模型建立了考虑行人随机行为的仿真模型.分析了随机行为对行人过街的影响,从速度和受力两个方面对行人随机行为进行建模,建立两个不同的行人随机行为模型.通过数值模拟,在双向行人比例1：1 的条件下,得到了考虑随机行为条件下行人的仿真轨迹和行人平均过街时间与行人总数的关系;此外在不同行人随机行为各向异性参数λ_αε 条件下,对比分析了仿真过街时间与经验模型过街时间.结果表明,行人随机行为导致过街时间增加,考虑随机行为后,改进模型二能够得到与实际相似的过街轨迹,当0.5<λ_αε <1时,改进模型二的行人仿真过街时间与利用经验模型得到的过街时间最为接近.     

基于车道建模的区域应急疏散路径规划

为有效解决应急疏散路线中存在的延误问题, 以总体疏散费用最小为目标, 以消除冲突点, 减少交织点, 并且以流量守恒、流量非负、节点和弧段的通行能力限制等为约束条件, 提出了基于车道层面的路网模型。利用Lingo软件, 分别对应用基于车道层面的疏散扩展网络流模型以及应用基于路段层面的节点-弧网络模型进行求解, 并以4个交叉口网络为例进行了对比分析。计算结果表明: 与应用基于路段层面的节点-弧网络模型相比, 应用基于车道层面的扩展网络流模型节约了4 h·veh^-1的出行费用, 出行成本降低了25%, 该模型在使疏散费用最小化的同时, 减少了交织情况产生的延误, 具有较高的疏散效率。     

城市道路交通信号控制的若干问题

针对我国城市道路交通信号控制中的灯色规定和一些常用信号正反两方面的影响因素等进行分析。首先提出我国现行交通法律法规对信号灯色规定的不足之处,然后对交通信号控制存在的基本问题进行重点研究。通过分析不同信号灯色（如机动车黄灯、红灯＋黄灯、绿闪、红闪,行人绿闪）及其他辅助设施（如倒计时信号）对交叉口交通安全和通行效率的影响,对信号灯色及倒计时信号设置提出方向性建议,并就道路交通安全法及其条例的补充、修订给出相应建议。最后,简要分析了信号控制领域应着重研究的若干理论和应用层面的问题,包括绿灯间隔时间、信号周期、转弯车辆控制策略、公交优先控制、自适应控制、干路协调控制等。