2025
Authors
Reza, S; Ferreira, MC; Machado, JJM; Tavares, JMRS;
Publication
EXPERT SYSTEMS
Abstract
An autonomous vehicle can sense its environment and operate without human involvement. Its adequate management in an intelligent transportation system could significantly reduce traffic congestion and overall travel time in a network. Adaptive traffic signal controller (ATSC) based on multi-agent systems using state-action-reward-state-action (SARSA (lambda)) are well-known state-of-the-art models to manage autonomous vehicles within urban areas. However, this study found inefficient weights updating mechanisms of the conventional SARSA (lambda) models. Therefore, it proposes a Gaussian function to regulate the eligibility trace vector's decay mechanism effectively. On the other hand, an efficient understanding of the state of the traffic environment is crucial for an agent to take optimal actions. The conventional models feed the state values to the agents through the MinMax normalization technique, which sometimes shows less efficiency and robustness. So, this study suggests the MaxAbs scaled state values instead of MinMax to address the problem. Furthermore, the combination of the A-star routing algorithm and proposed model demonstrated a good increase in performance relatively to the conventional SARSA (lambda)-based routing algorithms. The proposed model and the baselines were implemented in a microscopic traffic simulation environment using the SUMO package over a complex real-world-like 21-intersections network to evaluate their performance. The results showed a reduction of the vehicle's average total waiting time and total stops by a mean value of 59.9% and 17.55% compared to the considered baselines. Also, the A-star combined with the proposed controller outperformed the conventional approaches by increasing the vehicle's average trip speed by 3.4%.
2025
Authors
Oliveira, BB; Ahipasaoglu, SD;
Publication
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW
Abstract
Balancing supply and demand in free-floating one-way carsharing systems is a critical operational challenge. This paper presents a novel approach that integrates a binary logit model into a mixed integer linear programming framework to optimize short-term pricing and fleet relocation. Demand modeling, based on a binary logit model, aggregates different trips under a unified utility model and improves estimation by incorporating information from similar trips. To speed up the estimation process, a categorizing approach is used, where variables such as location and time are classified into a few categories based on shared attributes. This is particularly beneficial for trips with limited observations as information gained from similar trips can be used for these trips effectively. The modeling framework adopts a dynamic structure where the binary logit model estimates demand using accumulated observations from past iterations at each decision point. This continuous learning environment allows for dynamic improvement in estimation and decision-making. At the core of the framework is a mathematical program that prescribes optimal levels of promotion and relocation. The framework then includes simulated market responses to the decisions, allowing for real-time adjustments to effectively balance supply and demand. Computational experiments demonstrate the effectiveness of the proposed approach and highlight its potential for real-world applications. The continuous learning environment, combining demand modeling and operational decisions, opens avenues for future research in transportation systems.
2025
Authors
Carvalho, C; Pinho De Sousa, J; Santos, R; Marques, M;
Publication
Transportation Research Procedia
Abstract
By connecting maritime and land transport, container terminals play a critical role in global logistics systems, as part of broader intermodal networks. The evolution of containerisation and technological advances, along with increased demand and volumes, led to significant adaptations in these terminals, as a way to improve productivity, reduce costs and increase competitiveness, while coping with spatial and operational constraints. For strategic decision-making, managing these complex systems can be enhanced by simulation models allowing the analysis of different scenarios in dynamic, uncertain environments. This work, presents a simulation-based decision support tool developed in the FlexSim software, to analyse different container terminal configurations, with a particular focus on automation and on sustainable practices to reduce the energy consumption of terminals. A discrete event simulation model was developed to study multiple scenarios impacting productivity, resource utilisation, and waiting times. The proposed approach allows the test and evaluation of management strategies for port operations, with preliminary results showing that sizing and planning of the fleets of automated guided vehicles (AGV) can significantly affect the total operating time, the energy consumed, and the costs associated with battery charging operations. Future research should explore additional factors affecting container terminal operations, such as the reorganisation of the storage area, while incorporating optimisation elements for work planning and resource allocation. Moreover, the simulation model will be tested and validated in a real case study, designed for the Port of Sines in Portugal. © 2024 The Authors.
2025
Authors
Caetano, JA; De Sousa, JP; Marques, CM; Ribeiro, GM; Bahiense, L;
Publication
Transportation Research Procedia
Abstract
This research addresses the Frequency Setting Problem (FSP) together with vehicle technology selection for bus fleet sizing and management. A decision support tool was developed that combines a multi-criteria decision analysis, using the Analytic Hierarchy Process (AHP), and an enumeration procedure. The tool assists transportation operators in selecting optimal frequencies and vehicle technologies, considering economic, social, and environmental criteria. Computational experiments performed in the city of Niterói, Brazil, demonstrate the effectiveness of the tool. Scenarios with different criteria prioritizations highlight the flexibility of the approach and emphasize the need for a balance between all the sustainability dimensions. This approach positively impacts public transportation system performance, favouring higher-capacity vehicles while considering demand, and contributing to sustainable urban mobility. © 2024 The Authors.
2025
Authors
Alexandre Jesus; Arthur Jorge Pereira Corrêa; Miguel Vieira; Catarina Marques; Cristóvão Silva; Samuel Moniz;
Publication
Abstract
2025
Authors
Homayouni, SM; de Sousa, JP; Marques, CM;
Publication
WMU JOURNAL OF MARITIME AFFAIRS
Abstract
This paper examines the role of digital twins (DTs) in promoting sustainability within seaport operations and logistics. DTs have emerged as promising tools for enhancing seaport performance. Despite the recognized potential of DTs in seaports, there is a paucity of research on their practical implementation and impact on seaport sustainability. Through a systematic literature review, this study seeks to elucidate how DTs contribute to the sustainability of seaports and to identify future research and practical applications. We reviewed and categorized 68 conceptual and practical digital applications into ten core areas that effectively support economic, social, and environmental objectives in seaports. Furthermore, this paper proposes five preliminary potential applications for DTs where practical implementations are currently lacking. The primary findings indicate that DTs can enhance seaport sustainability by facilitating real-time monitoring and decision-making, improving safety and security, optimizing resource utilization, enhancing collaboration and communication, and supporting the development of the seaport ecosystem. Additionally, this study addresses the challenges associated with DT implementation, including high costs, conflicting stakeholder priorities, data quality and availability, and model validation. The paper concludes with a discussion of the implications for seaport managers and policymakers.
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