21,886 research outputs found

    National and international freight transport models: overview and ideas for further development

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    This paper contains a review of the literature on freight transport models, focussing on the types of models that have been developed since the nineties for forecasting, policy simulation and project evaluation at the national and international level. Models for production, attraction, distribution, modal split and assignment are discussed in the paper. Furthermore, the paper also includes a number of ideas for future development, especially for the regional and urban components within national freight transport models

    Route Planning in Transportation Networks

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    We survey recent advances in algorithms for route planning in transportation networks. For road networks, we show that one can compute driving directions in milliseconds or less even at continental scale. A variety of techniques provide different trade-offs between preprocessing effort, space requirements, and query time. Some algorithms can answer queries in a fraction of a microsecond, while others can deal efficiently with real-time traffic. Journey planning on public transportation systems, although conceptually similar, is a significantly harder problem due to its inherent time-dependent and multicriteria nature. Although exact algorithms are fast enough for interactive queries on metropolitan transit systems, dealing with continent-sized instances requires simplifications or heavy preprocessing. The multimodal route planning problem, which seeks journeys combining schedule-based transportation (buses, trains) with unrestricted modes (walking, driving), is even harder, relying on approximate solutions even for metropolitan inputs.Comment: This is an updated version of the technical report MSR-TR-2014-4, previously published by Microsoft Research. This work was mostly done while the authors Daniel Delling, Andrew Goldberg, and Renato F. Werneck were at Microsoft Research Silicon Valle

    Transport integration - an impossible dream?

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    Transport Integration and an Integrated Transport Policy have been widely espoused for many years, yet remain an ambiguous and ill-defined concept. After featuring strongly in the 1998 Transport Policy White Paper, recently transport integration has received less emphasis. However it appears it is set for a return under the new Transport Secretary, Lord Adonis.This paper explores the meaning of Integrated Transport. It concludes that there is no point in attempting to identify a single definition, but that there are overlapping layers of meaning, with higher levels incorporating lower, or narrower, understandings of the term Integrated Transport. This exploration of meanings of integration is a development of initial work (Potter and Skinner 2000) and is important as the alternative meanings lead to different transport policy responses. These meanings include: - Locational Integration: being able to easily change between transport modes (using Interchanges) - this is about services connecting in space - Timetabling Integration: Services at an interchange connect in time. - Ticketing Integration: Not needing to purchase a new ticket for each leg of a journey - Information Integration: Not needing to enquire at different places for each stage of a trip - or that different independent sources are easily connected - Service Design Integration: That the legal, administrative and governance structures permit/encouraging integration - Travel Generation Integration: Integrating the planning of transport with the generators of travel (particularly integration with land use planning) Furthermore, there are inherent tensions which make transport integration difficult to achieve. Only limited progress has been achieved in the UK since the 1998 White Paper, and even in Germany, with their strong transport policy structures, integration has failed (Schöller-Schwedes, 2009). This exploration of meanings will also explore the tensions involved as there is a danger of the UK chasing again a flawed concept

    On green routing and scheduling problem

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    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

    Personal security in travel by public transport : the role of traveller information and associated technologies

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    Acknowledgement This research reported in this paper has been funded by a grant award from the Engineering and Physical Sciences Research Council: EP/I037032/1.Peer reviewedPublisher PD

    FIVE STEPS TO RESPONSIBILITY

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    Responsibility has entered the academic discourse of logicians hardly more than few decades ago. I suggest a logical concept of responsibility which employs ideas both from a number of theories belonging to different branches of logic as well from other academic areas. As a comment to this concept, I suggest five steps narrative scenario in order to show how the logical dimension of responsibility emerges from diverse tendencies in logic and other sciences. Here are the five steps briefly stated: Step 1. Developing modal formalisms capable of evaluative analysis of situations (deontic, epistemic and etc.). Step 2. Drawing a conceptual borderline between normal and non-normal (weak) logical systems. Step 3. Using different kinds of models. Step 4. Agent- and action- friendly turn in logic. Step 5. Creating formalisms for modeling different types of agency. An idea advocated here within 5-Steps route to responsibility is that this concept is a complex causal and evaluative (axiological) relation. A logical account may be given for causal and normative aspects of this relation. Unfolding the responsibility back and forth through 5 Steps will result in different concepts. The technicalities are minimized for the sake of keeping the philosophical scope of the paper. For the same reason I also refrain from discussing legal and juridical ramifications of the issue

    Agent-based modelling of air transport demand

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    Constraints such as opening hours or passenger capacities influence travel options that can be offered by an airport and by the connecting airlines. If infrastructure, policy or technological measures modify transport options, then the benefits do not only depend on the technology, but also on possibly heterogeneous user preferences such as desired arrival times or on the availability of alternative travel modes. This paper proposes an agent-based, iterative assignment procedure to model European air traffic and German passenger demand on a microscopic level, capturing individual passenger preferences. Air transport technology is simulated microscopically, i.e. each aircraft is represented as single unit with attached attributes such as departure time, flight duration or seat availability. Trip-chaining and delay propagation can be added. Microsimulation is used to verify and assess passengers’ choices of travel alternatives, where those choices improve over iterations until an agent-based stochastic user equilibrium is reached. This requires fast simulation models, thus, similar to other approaches in air traffic modelling a queue model is used. In contrast to those approaches, the queue model in this work is solved algorithmically. Overall, the approach is suited to analyze, forecast and evaluate the consequences of mid-distance transport measures
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