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Integrated operator and user-based rebalancing and recharging in dockless shared e-micromobility systems 无桩共享电动交通系统中基于运营商和用户的综合再平衡和再充电功能
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-26 DOI: 10.1016/j.commtr.2024.100155
Elnaz Emami, Mohsen Ramezani
This study proposes a rebalancing method for a dockless e-micromobility sharing system, employing both trucks and users. Platform-owned trucks relocate and recharge e-micromobility vehicles using battery swapping technology. In addition, some users intending to rent an e-micromobility vehicle are offered incentives to end their trips in defined locations to assist with rebalancing. The integrated formulation of rebalancing and recharging accounts for each e-micromobility vehicle's characteristics, such as location and charge level. The problem is formulated as a mixed binary problem, which minimizes operational costs and total unmet demand while maximizing the system's profit. To solve the optimization problem, a Branch and Bound method is employed. Rebalancing decisions and routing plans of each truck are obtained by solving the optimization problem. We simulate an on-demand shared e-micromobility system with the proposed integrated rebalancing method and conduct numerical studies. The results indicate that the proposed method enhances system performance and user travel times.
本研究提出了一种无桩电动移动共享系统的再平衡方法,同时使用卡车和用户。平台所属的卡车利用电池交换技术为电动车重新定位和充电。此外,一些打算租用电动车的用户还可获得奖励,在指定地点结束行程,以帮助实现再平衡。重新平衡和充电的综合表述考虑到了每辆电动微型车的特点,如位置和充电水平。该问题被表述为混合二元问题,即在最大化系统利润的同时,最小化运营成本和未满足的总需求。为解决优化问题,采用了分支和边界法。通过求解优化问题,可以获得重新平衡决策和每辆卡车的路线计划。我们利用所提出的综合再平衡方法模拟了一个按需共享电动交通系统,并进行了数值研究。结果表明,建议的方法提高了系统性能和用户出行时间。
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引用次数: 0
Unveiling the determinants of battery electric vehicle performance: A systematic review and meta-analysis 揭示电池电动汽车性能的决定因素:系统回顾与荟萃分析
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-25 DOI: 10.1016/j.commtr.2024.100148
Fangjie Liu , Muhammad Shafique , Xiaowei Luo
The transition toward battery electric vehicles (BEVs) is a critical element in the global shift toward sustainable transportation. This meta-analysis delves into the multifaceted factors influencing BEV performance, including environmental, technological, behavioral, and political-economic determinants. The purpose of this review is to systematically organize and assess how these factors impact BEV efficiency and sustainability across various operational scenarios, such as driving, charging, and decommissioning. By examining a wide range of literature, this study constructs a comprehensive framework that categorizes the primary components and performance metrics, revealing complex relationships and potential causal connections. The findings highlight that although technological advancements and regulatory frameworks are the predominant drivers of BEV performance, environmental conditions and user behaviors also play significant roles. The key emerging topics identified suggest further research avenues, particularly in optimizing battery technology and expanding policy support. Additionally, the analysis provides new and systematic insights compared with previous reviews, offering a clearer understanding of the determinants, their impacts, and the interactions between them. These insights are crucial for developing a transparent evaluation system for future research and policy formulation. This comprehensive synthesis not only aids in understanding the current landscape but also in directing future scholarly and practical endeavors in electric vehicle research.
向电池电动汽车(BEV)过渡是全球向可持续交通转变的关键因素。本荟萃分析深入研究了影响 BEV 性能的多方面因素,包括环境、技术、行为和政治经济决定因素。本综述旨在系统整理和评估这些因素如何在驾驶、充电和退役等各种运行场景中影响 BEV 的效率和可持续性。通过研究大量文献,本研究构建了一个综合框架,对主要成分和性能指标进行了分类,揭示了复杂的关系和潜在的因果联系。研究结果突出表明,虽然技术进步和监管框架是推动电动汽车性能的主要因素,但环境条件和用户行为也发挥着重要作用。确定的关键新兴课题提出了进一步的研究途径,特别是在优化电池技术和扩大政策支持方面。此外,与之前的综述相比,该分析提供了新的系统性见解,使人们对决定因素、其影响以及它们之间的相互作用有了更清晰的认识。这些见解对于为未来研究和政策制定建立透明的评估系统至关重要。这份全面的综述不仅有助于了解当前的状况,也有助于指导未来电动汽车研究的学术和实践活动。
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引用次数: 0
Integrating machine learning and extreme value theory for estimating crash frequency-by-severity via AI-based video analytics 整合机器学习和极值理论,通过基于人工智能的视频分析,按严重程度估算碰撞频率
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-14 DOI: 10.1016/j.commtr.2024.100147
Fizza Hussain , Yuefeng Li , Md Mazharul Haque
Traffic conflict techniques rely heavily on the proper identification of conflict extremes, which directly affects the prediction performance of extreme value models. Two sampling techniques, namely, block maxima and peak over threshold, form the core of these models. Several studies have demonstrated the inefficacy of extreme value models based on these sampling approaches, as their crash estimates are too imprecise, hindering their widespread practical use. Recently, anomaly detection techniques for sampling conflict extremes have been used, but their application has been limited to estimating crash frequency without considering the crash severity aspect. To address this research gap, this study proposes a hybrid model of machine learning and extreme value theory within a bivariate framework of traffic conflict measures to estimate crash frequency by severity level. In particular, modified time-to-collision (MTTC) and expected post-collision change in velocity (Delta-V or ΔV) have been proposed in the hybrid modeling framework to estimate rear-end crash frequency by severity level. Rear-end conflicts were identified through artificial intelligence-based video analytics for three four-legged signalized intersections in Brisbane, Australia, using four days of data. Non-stationary bivariate hybrid generalized extreme value models with different anomaly detection/sampling techniques (isolation forest and minimum covariance determinant) were developed. The non-stationarity of traffic conflict extremes was handled by parameterizing model parameters, including location, scale, and both location and scale parameters simultaneously. The results indicate that the bivariate hybrid models can estimate severe and non-severe crashes when compared with historical crash records, thereby demonstrating the viability of the proposed approach. A comparative analysis of two anomaly techniques reveals that the isolation forest model marginally outperforms the minimum covariance determinant model. Overall, the modeling framework presented in this study advances conflict-based safety assessment, where the severity dimension can be captured via bivariate hybrid models.
交通冲突技术在很大程度上依赖于冲突极值的正确识别,这直接影响到极值模型的预测性能。两种取样技术,即街区最大值和峰值超过阈值,构成了这些模型的核心。一些研究表明,基于这些抽样方法的极值模型效果不佳,因为其碰撞估计值过于不精确,阻碍了其广泛的实际应用。最近,人们开始使用异常检测技术对冲突极值进行采样,但其应用仅限于估算碰撞频率,而没有考虑碰撞严重性方面。针对这一研究空白,本研究在交通冲突测量的双变量框架内提出了一种机器学习和极值理论的混合模型,用于按严重程度估算碰撞频率。特别是,在混合模型框架中提出了修正碰撞时间(MTTC)和预期碰撞后速度变化(Delta-V 或 ΔV),用于按严重程度估算追尾碰撞频率。通过基于人工智能的视频分析,利用四天的数据对澳大利亚布里斯班的三个四脚信号灯交叉路口的追尾冲突进行了识别。利用不同的异常检测/采样技术(隔离林和最小协方差行列式)开发了非稳态双变量混合广义极值模型。交通冲突极值的非平稳性是通过对模型参数进行参数化处理的,包括位置参数、规模参数,以及同时对位置参数和规模参数进行参数化处理。结果表明,与历史碰撞记录相比,双变量混合模型可以估算严重和非严重碰撞事故,从而证明了所提方法的可行性。对两种异常技术的比较分析表明,隔离林模型略优于最小协方差行列式模型。总体而言,本研究提出的建模框架推进了基于冲突的安全评估,其中严重性维度可通过二元混合模型来捕捉。
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引用次数: 0
Bridging the gap: Toward a holistic understanding of shared micromobility fleet development dynamics 缩小差距:全面了解共享微型机动性车队的发展动态
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-13 DOI: 10.1016/j.commtr.2024.100149
Shahnaz N. Fuady , Paul C. Pfaffenbichler , Yusak O. Susilo
Rapid urbanization and shifting demographics worldwide necessitate innovative urban transportation solutions. Shared micromobility systems, such as bicycle- and scooter-sharing programs, have emerged as promising alternatives to traditional urban mobility challenges. This study delves into the complexity of shared micromobility fleet development, focusing on the interplay between fleet size, user demand, regulatory frameworks, economic viability, and public engagement. By employing a system dynamics modeling approach that incorporates causal loop diagrams (CLDs) and stock and flow models (SFMs), we explore various policy scenarios to optimize micromobility management systems. Our findings reveal that financial incentives, such as fee reductions and government subsidies, significantly increase user adoption and profitability, whereas increased operational fees necessitate a delicate balance between cost management and service attractiveness. Sensitivity and uncertainty analyses highlight critical parameters for effective fleet management. This research offers actionable insights for policymakers and operators, promoting sustainable urban transport systems.
全球范围内的快速城市化和人口结构的不断变化要求我们采用创新的城市交通解决方案。共享微型交通系统,如自行车和滑板车共享项目,已成为应对传统城市交通挑战的有前途的替代方案。本研究深入探讨了共享微型交通车队发展的复杂性,重点关注车队规模、用户需求、监管框架、经济可行性和公众参与之间的相互作用。通过采用系统动力学建模方法,结合因果循环图(CLDs)和存量与流量模型(SFMs),我们探索了优化微型交通管理系统的各种政策方案。我们的研究结果表明,减免费用和政府补贴等财政激励措施能显著提高用户采用率和盈利能力,而增加运营费用则需要在成本管理和服务吸引力之间取得微妙的平衡。敏感性和不确定性分析强调了有效车队管理的关键参数。这项研究为政策制定者和运营商提供了可行的见解,促进了可持续城市交通系统的发展。
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引用次数: 0
Modular flying vehicles: Scheduling modes, social benefits, and challenges 模块化飞行器:调度模式、社会效益和挑战
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-07 DOI: 10.1016/j.commtr.2024.100144
Di Lv, Yuhao Wang, Liang Wang, Yang Fei, Kai Wang, Xiaobo Qu
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引用次数: 0
Harnessing multimodal large language models for traffic knowledge graph generation and decision-making 利用多模态大语言模型生成交通知识图谱并进行决策
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-06 DOI: 10.1016/j.commtr.2024.100146
Senyun Kuang, Yang Liu, Xin Wang, Xinhua Wu, Yintao Wei
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引用次数: 0
Controllability test for nonlinear datatic systems 非线性数据系统的可控性测试
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-04 DOI: 10.1016/j.commtr.2024.100143
Yujie Yang , Letian Tao , Likun Wang, Shengbo Eben Li
Controllability is a fundamental property of control systems, serving as the prerequisite for controller design. While controllability test is well established in modelic (i.e., model-driven) control systems, extending it to datatic (i.e., data-driven) control systems is still a challenging task due to the absence of system models. In this study, we propose a general controllability test method for nonlinear systems with datatic description, where the system behaviors are merely described by data. In this situation, the state transition information of a dynamic system is available only at a limited number of data points, leaving the behaviors beyond these points unknown. Different from traditional exact controllability, we introduce a new concept called ϵ-controllability, which extends the definition from point-to-point form to point-to-region form. Accordingly, our focus shifts to checking whether the system state can be steered to a closed state ball centered on the target state, rather than exactly at that target state. Given a known state transition sample, the Lipschitz continuity assumption restricts the one-step transition of all the points in a state ball to a small neighborhood of the subsequent state. This property is referred to as one-step controllability backpropagation, i.e., if the states within this neighborhood are ϵ-controllable, those within the state ball are also ϵ-controllable. On its basis, we propose a tree search algorithm called maximum expansion of controllable subset (MECS) to identify controllable states in the dataset. Starting with a specific target state, our algorithm can iteratively propagate controllability from a known state ball to a new one. This iterative process gradually enlarges the ϵ-controllable subset by incorporating new controllable balls until all ϵ-controllable states are searched. Besides, a simplified version of MECS is proposed by solving a special shortest path problem, called Floyd expansion with radius fixed (FERF). FERF maintains a fixed radius of all controllable balls based on a mutual controllability assumption of neighboring states. The effectiveness of our method is validated in three datatic control systems whose dynamic behaviors are described by sampled data.
可控性是控制系统的基本属性,是控制器设计的先决条件。虽然可控性测试已在模型(即模型驱动)控制系统中得到广泛应用,但由于缺乏系统模型,将其扩展到数据(即数据驱动)控制系统仍是一项具有挑战性的任务。在本研究中,我们提出了一种针对数据描述非线性系统的通用可控性测试方法,即系统行为仅由数据描述。在这种情况下,动态系统的状态转换信息只能在有限的数据点上获得,而这些点以外的行为则是未知的。与传统的精确可控性不同,我们引入了一个名为ϵ-可控性的新概念,它将定义从点到点形式扩展到点到区域形式。因此,我们的重点转移到检查系统状态是否能被引导到以目标状态为中心的闭合状态球上,而不是精确到目标状态。给定一个已知的状态转换样本,Lipschitz 连续性假设将状态球中所有点的一步转换限制在后续状态的一个小邻域内。这一特性被称为一步可控性反向传播,即如果该邻域内的状态是ϵ可控的,则状态球内的状态也是ϵ可控的。在此基础上,我们提出了一种名为 "可控子集最大扩展"(MECS)的树搜索算法,用于识别数据集中的可控状态。从一个特定的目标状态开始,我们的算法可以迭代地将可控性从一个已知的状态球传播到一个新的状态球。这一迭代过程通过加入新的可控状态球,逐渐扩大ϵ可控子集,直至搜索到所有ϵ可控状态。此外,还提出了一种简化版的 MECS,即求解一个特殊的最短路径问题,称为半径固定的 Floyd 扩展(FERF)。FERF 基于相邻状态的相互可控性假设,保持所有可控球的固定半径。我们在三个数据控制系统中验证了这一方法的有效性,这些系统的动态行为由采样数据描述。
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引用次数: 0
Intelligent vehicle platooning transit 智能车辆排队过境
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-11-04 DOI: 10.1016/j.commtr.2024.100145
Chi Xie, Ziyu Zhang, Aijing Su, Bing Wu
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引用次数: 0
A multi-functional simulation platform for on-demand ride service operations 按需乘车服务运营的多功能模拟平台
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-10-21 DOI: 10.1016/j.commtr.2024.100141
Siyuan Feng , Taijie Chen , Yuhao Zhang , Jintao Ke , Zhengfei Zheng , Hai Yang
On-demand ride services or ride-sourcing services have been experiencing fast development and steadily reshaping the way people travel in the past decade. Various optimization algorithms, including reinforcement learning approaches, have been developed to help ride-sourcing platforms design better operational strategies to achieve higher efficiency. However, due to cost and reliability issues, it is commonly infeasible to validate these models and train/test these optimization algorithms within real-world ride-sourcing platforms. Acting as a proper test bed, a simulation platform for ride-sourcing systems will thus be essential for both researchers and industrial practitioners. While previous studies have established simulators for their tasks, they lack a fair and public platform for comparing the models/algorithms proposed by different researchers. In addition, the existing simulators still face many challenges, ranging from their closeness to real environments of ride-sourcing systems to the completeness of tasks they can implement. To address the challenges, we propose a novel simulation platform for ride-sourcing systems on real transportation networks. It provides a few accessible portals to train and test various optimization algorithms, especially reinforcement learning algorithms, for a variety of tasks, including on-demand matching, idle vehicle repositioning, and dynamic pricing. Evaluated on real-world data-based experiments, the simulator is demonstrated to be an efficient and effective test bed for various tasks related to on-demand ride service operations.
按需乘车服务或乘车外包服务在过去十年中经历了快速发展,并稳步重塑了人们的出行方式。包括强化学习方法在内的各种优化算法已被开发出来,以帮助乘车外包平台设计更好的运营策略,从而实现更高的效率。然而,由于成本和可靠性问题,在现实世界的乘车外包平台中验证这些模型和训练/测试这些优化算法通常是不可行的。因此,作为一个合适的测试平台,乘车外包系统仿真平台对研究人员和工业从业人员都至关重要。虽然之前的研究已经为其任务建立了模拟器,但它们缺乏一个公平、公开的平台来比较不同研究人员提出的模型/算法。此外,现有的模拟器还面临着许多挑战,从是否贴近真实的乘车外包系统环境到所能实现任务的完整性等。为了应对这些挑战,我们提出了一个新颖的真实交通网络上的乘车外包系统模拟平台。它提供了几个可访问的门户,用于训练和测试各种优化算法,特别是强化学习算法,以完成各种任务,包括按需匹配、闲置车辆重新定位和动态定价。通过基于真实世界数据的实验评估,证明该模拟器是按需乘车服务运营相关各种任务的高效测试平台。
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引用次数: 0
Traffic expertise meets residual RL: Knowledge-informed model-based residual reinforcement learning for CAV trajectory control 交通专业知识与残差 RL 的结合:基于知识模型的残差强化学习用于 CAV 轨迹控制
IF 12.5 Q1 TRANSPORTATION Pub Date : 2024-10-18 DOI: 10.1016/j.commtr.2024.100142
Zihao Sheng, Zilin Huang, Sikai Chen
Model-based reinforcement learning (RL) is anticipated to exhibit higher sample efficiency than model-free RL by utilizing a virtual environment model. However, obtaining sufficiently accurate representations of environmental dynamics is challenging because of uncertainties in complex systems and environments. An inaccurate environment model may degrade the sample efficiency and performance of model-based RL. Furthermore, while model-based RL can improve sample efficiency, it often still requires substantial training time to learn from scratch, potentially limiting its advantages over model-free approaches. To address these challenges, this paper introduces a knowledge-informed model-based residual reinforcement learning framework aimed at enhancing learning efficiency by infusing established expert knowledge into the learning process and avoiding the issue of beginning from zero. Our approach integrates traffic expert knowledge into a virtual environment model, employing the intelligent driver model (IDM) for basic dynamics and neural networks for residual dynamics, thus ensuring adaptability to complex scenarios. We propose a novel strategy that combines traditional control methods with residual RL, facilitating efficient learning and policy optimization without the need to learn from scratch. The proposed approach is applied to connected automated vehicle (CAV) trajectory control tasks for the dissipation of stop-and-go waves in mixed traffic flows. The experimental results demonstrate that our proposed approach enables the CAV agent to achieve superior performance in trajectory control compared with the baseline agents in terms of sample efficiency, traffic flow smoothness and traffic mobility.
通过利用虚拟环境模型,基于模型的强化学习(RL)有望比无模型强化学习表现出更高的采样效率。然而,由于复杂系统和环境中的不确定性,获得足够准确的环境动态表征具有挑战性。不准确的环境模型可能会降低基于模型的 RL 的采样效率和性能。此外,虽然基于模型的 RL 可以提高采样效率,但它通常仍需要大量的训练时间来从头开始学习,这可能会限制它相对于无模型方法的优势。为了应对这些挑战,本文介绍了一种基于知识的模型残差强化学习框架,旨在通过在学习过程中注入已有的专家知识来提高学习效率,避免从零开始的问题。我们的方法将交通专家知识整合到虚拟环境模型中,采用智能驾驶员模型(IDM)来处理基本动态,采用神经网络来处理残差动态,从而确保对复杂场景的适应性。我们提出了一种新颖的策略,将传统控制方法与残差 RL 相结合,促进高效学习和策略优化,而无需从头开始学习。我们将所提出的方法应用于联网自动驾驶汽车(CAV)的轨迹控制任务,以消除混合交通流中的走走停停现象。实验结果表明,与基线代理相比,我们提出的方法使 CAV 代理在样本效率、交通流平稳性和交通流动性方面实现了更优越的轨迹控制性能。
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引用次数: 0
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Communications in Transportation Research
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