13,278 research outputs found
Long-Term Consequences of Congestion Pricing: A Small Cordon in the Hand Is Worth Two in the Bush
We evaluate and compare the long-term economic effects of three cordon-based road pricing schemes applied to the Washington, DC, metropolitan area. To conduct this analysis, we employ a spatially disaggregated general equilibrium model of a regional economy that incorporates the decisions of residents, firms, and developers, integrated with a spatially disaggregated strategic transportation planning model that features mode, time period, and route choice. We find that all cordon pricing schemes increase welfare of the residents, as well as lead to GDP growth. At the optimum, the larger cordon and a double cordon lead to higher benefits than the small cordon encompassing downtown core. Nevertheless, the small cordon seems to be a safer bet because when the toll charge is set suboptimally, the net benefits from the small cordon compared to the optimum change negligibly, while the net benefits from the larger cordon decline sharply as the charge deviates from the optimal level.traffic congestion, cordon tolls, land use, welfare analysis, road pricing, general equilibrium, simulation, Washington DC
Vertical integration and firm boundaries : the evidence
Since Ronald H. Coase's (1937) seminal paper, a rich set of theories has been developed that deal with firm boundaries in vertical or input–output structures. In the last twenty-five years, empirical evidence that can shed light on those theories also has been accumulating. We review the findings of empirical studies that have addressed two main interrelated questions: First, what types of transactions are best brought within the firm and, second, what are the consequences of vertical integration decisions for economic outcomes such as prices, quantities, investment, and profits. Throughout, we highlight areas of potential cross-fertilization and promising areas for future work
On green routing and scheduling problem
The vehicle routing and scheduling problem has been studied with much
interest within the last four decades. In this paper, some of the existing
literature dealing with routing and scheduling problems with environmental
issues is reviewed, and a description is provided of the problems that have
been investigated and how they are treated using combinatorial optimization
tools
Task Assignment and Path Planning for Autonomous Mobile Robots in Stochastic Warehouse Systems
The material handling industry is in the middle of a transformation from manual operations to automation due to the rapid growth in e-commerce. Autonomous mobile robots (AMRs) are being widely implemented to replace manually operated forklifts in warehouse systems to fulfil large shipping demand, extend warehouse operating hours, and mitigate safety concerns. Two open questions in AMR management are task assignment and path planning. This dissertation addresses the task assignment and path planning (TAPP) problem for autonomous mobile robots (AMR) in a warehouse environment. The goals are to maximize system productivity by avoiding AMR traffic and reducing travel time. The first topic in this dissertation is the development of a discrete event simulation modeling framework that can be used to evaluate alternative traffic control rules, task assignment methods, and path planning algorithms. The second topic, Risk Interval Path Planning (RIPP), is an algorithm designed to avoid conflicts among AMRs considering uncertainties in robot motion. The third topic is a deep reinforcement learning (DRL) model that is developed to solve task assignment and path planning problems, simultaneously. Experimental results demonstrate the effectiveness of these methods in stochastic warehouse systems
Voyager spacecraft phase B, task D. Volume 2 - System description. Book 5 - Final report
Voyager spacecraft design standards, and operational support and mission-dependent equipment requirement
Milk Run Design: Definitions, Concepts and Solution Approaches
Efficient inbound networks in the European automotive industry rely on a set of different transport concepts including milk runs - understood as regularly scheduled pickup tours. The complexity of designing such a mixed network makes decision support necessary: In this thesis we provide definitions, mathematical models and a solution method for the Milk Run Design problem and introduce indicators assessing the performance of established milk runs in relation to alternative transport concepts
Milk Run Design: Definitions, Concepts and Solution Approaches
Efficient inbound networks in the European automotive industry rely on a set of different transport concepts including milk runs - understood as regularly scheduled pickup tours. The complexity of designing such a mixed network makes decision support necessary: In this book we provide definitions, mathematical models and a solution method for the Milk Run Design problem and introduce indicators assessing the performance of established milk runs in relation to alternative transport concepts
Vertical Integration and Firm Boundaries : The Evidence
Understanding what determines firm boundaries and the choice between interacting in a firm or a market is not only the fundamental concern of the theory of the firm, but it is also one of the most important issues in economics. Data on value added, for example, reveal that in the US, transactions that occur in firms are roughly equal in value to those that occur in markets. The economics profession, however, has devoted much more attention to the workings of markets than to the study of firms, and even less attention to the interface between the two. Nevertheless, since Coase’s (1937) seminal paper on the subject, a rich set of theories has been developed that deal with firm boundaries in vertical or input/output structures. Furthermore, in the last 25 years, empirical evidence that can shed light on those theories has been accumulating.Vertical integration ; firm boundaries ; vertical mergers ; firms versus markets
Importance of freight mode choice criteria: An MCDA approach
Road transportation has been the dominant mode for inland freight transportation for decades. Rail and waterways transportation are less frequently used alternatives, but in general more attractive from an environmental perspective. Even though many policies promoting the use of intermodal transportation have been proposed, they have had little impact to trigger shippers to shift mode from road transportation to rail or inland waterways transportation. One main reason might be that the requirements of shippers towards transportation modes are still not well understood. Hence this research investigates freight transportation mode choice with a new approach, multi-criteria decision analysis, as well as from the perspectives of different types of industries and experts. Reviewing the literature, the requirements for transportation modes are abstracted into a set of criteria, including transportation cost, door-to-door travel time, on-time reliability, flexibility, frequency, and reduction of CO2 emissions. As the importance of these factors might be different for different industries, we consider four segments: the manufacturing industry, the agriculture industry, the perishable food industry, and the chemical industry. Data from practitioners, industry experts, and academics are collected via online questionnaires and analyzed using the ‘best worst method’ (BWM) to identify weights for the mentioned criteria. The results indicate that transportation cost is viewed as the most important, closely followed by on-time reliability, while reduction of CO2 emission is viewed as the least important. Several comparison studies are conducted to see any difference in the importance of these factors with respect to different industries or respondent groups
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