1,720,965 research outputs found
A multi-objective optimization approach for disruption management in an intermodal freight transport network
No full textThe growing demand for freight transportation is leading to pay more attention to the management of intermodal freight transport network (IFTN). The optimization of IFTN management will have many benefits in terms of sustainability, reducing costs and pollution. Although many studies on the optimization of IFTN operations exist, the management of disruptions deserves a particular attention since disruptions may lead to a significant drop of performance in the entire network. In particular, seaport terminals are prone to disruptions because of their key role in connecting the land side and the sea-side operations. The availability and reliability of the entire network is directly affected by their disruptions. In this paper, a multi-objective linear programming model is developed to minimize congestion in an IFTN, which is originated from the occurrence of a disruption in a seaport terminal. The model aims to minimize cost and emissions, simultaneously. Computational results of a realistic case study, inspired by an Italian IFTN, shows the effectiveness of the developed model to improve the performance of the entire network
Case Studies on Transport Policy
Full text linkTransport policy is a multidisciplinary field where engineering, economics, sociology and law must come together in well-articulated and effective solutions. Despite being a field of effective intervention, most scientific publications address transport policy with a theoretical and often abstract approach, making its understanding difficult for non-senior academics and even more opaque for practitioners. While the merits of case study methods both for undergraduate and graduate teaching are recognised, academics struggle to find empirical material that provides objective and operational illustration of the theories and approaches lectured. This is a major barrier not only in the teaching context but also for practitioners.
Case Studies on Transport Policy covers this gap by providing a repository of relevant material to support teaching and transferability of experiences. Observation of field experience highlighting the details and drawbacks of implementation is invaluable to show how Transport Policy can be applied in the operational field, maintaining consistency with strategic options. Teaching with case studies introduces students to challenges they may face in the real world, and provides a very rich learning method for executive training at every institutional level. For practitioners, and specially governments, case studies are a powerful tool to show the potential benefits from policy measures and packages.
Case Studies on Transport Policy and its sister journal Transport Policy provide a valuable reference for the specialised study of transport policy offering in-depth theoretical analysis and detailed case study description and analysis, and in this way providing very complete material for decision makers planners and practitioners to undertake transferability of experiences
Real-time monitoring of the longitudinal strain of Continuous Welded Rail for safety improvement
No full textContinuous welded rail maintenance plays a significant role in ensuring high levels of rail traffic and safety. Temperature variations, excessive alignment defects, decreased fastening system resistance and train braking (always in the same stretches and in the same direction) may result in rail buckling or rail breaks. The current traditional monitoring systems and procedures for continuous welded rail consist of programmed discontinuous diagnostic surveys that require personnel intervention on site. Moreover, these traditional systems often imply destructive and invasive operations on the track that may lead to interruption of railway operations. This paper proposes a Rail Strain Monitoring System (RSMS) that performs a real-time rail strain monitoring and allows rail inspection without personnel on site. Using strain gauges and temperature sensors, placed on the rail in specific measurement points, the proposed Rail Strain Monitoring System performs a multi-parameter check by measuring, at the same time, the temperature, the rail strain and the neutral temperature of the rail. The paper describes the mode of operation of the Rail Strain Monitoring System, the calibration procedure and the results from the field, and highlights the advantages of this system in comparison to other traditional monitoring systems. The safety improvement that can be achieved with the application of the Rail Strain Monitoring System is analysed. In particular, the reliability of the system is evaluated and compared to the human error probability in the traditional manual inspections. Finally, the reduction of derailment risk and related economic damages is estimated
On exploring the potentialities of autonomous vehicles in urban spatial planning
No full textSustainability is nowadays an overarching concept for transport policy and planning around the world. Focusing on urban areas, the problem of congestion, combined with the need to reduce emissions into the atmosphere and increase road safety, has led national and European administrations to develop initiatives to support the so-called "soft mobility" (i.e., the mobility of pedestrians, cyclists). On the other hand, the introduction of autonomous vehicles will lead to significant changes in the interaction between traffic flow and infrastructure. Given this premise, the aim of this paper consists of modelling the interaction between urban space and autonomous vehicles mobility to explore possible benefits deriving by their market penetration. In detail, the paper presents a network design problem able to optimally identify which links of the road network can be considered superfluous in an autonomous vehicle scenario and, therefore, can be eliminated, to reuse them for the soft mobility. A case study is presented to show the proposed network design approach
On planning highway maintenance considering the impact on traffic flow due to different work zone configurations
No full textHighway maintenance is key to achieve high transportation network performance. However, the presence of work zones represents a disruptive event for the traffic flow. In particular, different work zone configurations have different impacts on traffic. Hence, providing a decision support tool to optimize the maintenance planning process on the highways is necessary to mitigate the impacts of work zones on traffic flow. In this paper, a novel approach is presented which considers the maintenance efficiency, the work zone configurations and the transport demand. The proposed approach applied traffic simulation to investigate traffic impacts of different work zone configurations along the network. Then the microscopic fundamental traffic characteristics, obtained from the simulation, are used as an input for the Mixed-Integer Linear Programming (MILP) model to optimize and prioritize the maintenance operations. The proposed approach is applied to a real case study in an Italian highway network. Results indicate the effectiveness and applicability of the proposed approach
Reshaping metro station spaces to improve social distancing during COVID-19 pandemic
No full textPedestrian flow management and control inside stations are becoming key topics in order to avoid congestion phenomena and to guarantee the required social distancing during the pandemic emergency. In this context, this paper is aimed at developing simulation-based optimization and control strategies able to take into account space discretization and capacity constraints. In particular, a two-stage model is applied. The first stage consists in a network design model for the identification of the station layout, while the second stage consists in a simulation-based model to verify the performance of the identified control strategy. The application of the proposed approach to a metro station of the Italian city of Genoa is described to show its usefulness and applicability to a real-world scenario
Integrated Approach for Convoy Dispatching and Passenger Routing at Railway Stations with Variable Composition Trains
No full textThis paper addresses a railway scenario with variable composition trains, and focuses on the management and simulation of the passenger flows and trains at stations. In particular, it proposes a management system aimed at optimally routing the passengers from their entrance in the station to the correct platform segment according the train they have to board, and scheduling the train service in terms of convoy composition, capacity and destinations. The resulting system is then modelled as a discrete event system (DES) and simulated, to evaluate its performance on the basis of indicators like the queue length, the unsatisfied demand, the passenger travel time in the station, and the passenger density at the platform. The proposed station management system is then tested on a mixed real/synthetic numerical example aimed at proving the feasibility and functioning of the proposed approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
High Density - HD Using ERTMS: The Italian Solution for the Railway Traffic Management
No full textThe HD ERTMS solution for railway traffic management is presented. It allows to achieve 'high density' railway traffic, increasing the number of trains on the existing railway lines. The proposed solution is based on the ERTMS technological standard and can be integrated with existing signaling systems minimizing field intervention: HD ERTMS trains do not interfere with trains equipped by other signaling and train separation systems. The railway traffic simulation software RFI NET has been upgraded to verify HD ERTMS potentiality and to optimize rail traffic on lines, nodes and stations. Finally, results of the first HD ERTMS application to the Italian railway node of Florence are presented
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