1,721,062 research outputs found
Towards the Physical Internet with Coloured Petri Nets
No full textColoured Petri Nets can be a valuable and powerful tool to design, analyse, and
control the subsystems composing the Physical Internet, as they are able to capture the
precedence relations and interactions among events which characterize the facilities and
infrastructures (multimodal logistics centres and hubs, transit centres, roads and railways)
through which p-containers are delivered. In this paper, the use of Coloured Petri Nets in the
field of the Physical Internet is discussed and an example of the application of such a modelling
tool to a multimodal hub in the PI is provided. The multimodal hub consists of four areas: a
port area at which vessels arrive and depart, a train terminal for rail transportation, a road
terminal for truck-to-X (and vice-versa) transhipment, and a storage area. The storage area
and the road terminal are considered in detail, and two nets representing a section of a pconveyor
and a p-sorter/p-composer are proposed to illustrate the applicability of the CPN
formalism to the Physical Internet paradigm
A Methodological Framework for Determination of Public Transport Accessibility Index
No full textRapid urbanization along with the population growth increases the pressure on existing transportation systems which boosts the needs for the provision of a well-connected and efficient Public Transport Systems (PTSs) to meet the mobility needs of the people. In this framework, it is important for the PTSs of a region to perform at certain quality levels including availability (both spatial and temporal), accessibility, affordability, environmental protection etc. Among all these features, the most important is the accessibility to stops since access to/from the public transport is provided only through them. This paper is focused on the development of a novel methodology to evaluate the accessibility of public transport at different levels of measurements of a region/city using Public Transport Accessibility Index (PTAI). It is developed based on the accessibility of public transport stops to the population, service centers and connectivity to nearby regions. The proposed approach is effective in terms of highlighting the least accessible areas towards the improvement of existing public transport connections or planning of new services. An application of proposed methodology has been presented using a mathematical example
Management of Public Transportation Demand and Maximization of Operator Revenues using Car Sharing as a Supplement to Public Transport Systems
No full textPublic Transport (PT) systems of a region serve as key players in satisfying the mobility needs of people. Nevertheless, the rapid urbanization and population growth increases the pressure on existing PT infrastructure in terms of effectively meeting additional passenger demand and a failure in this goal will result into users' shift to their private vehicles with consequent worsening of the congestion problems along with other environmental impacts. In this framework, it has been observed that providing more and more PT options, is not always a viable solution due to limited street space and large investments required for their operations. To tackle with this issue, shared mobility services such as car sharing, ride sharing, and other micro mobility services have proved to be a feasible solution.Considering these facts, this paper is focused on the design of Car Sharing (CS) systems as a supplement to PT to attract the additional demand for PT systems of a region. To do so, an optimization model is stated as Mixed Integer Linear Programming (MILP) model, aiming at minimizing the unserved demand for PT in each zone but maximizing, at the same time, the operator's revenues. The effectiveness of the proposed mathematical model is supported using a numerical example
Decidability results in First-Order Hybrid Petri Nets
Full text linkIn this paper we tackle the decidability of marking reachability for a hybrid formalism based on Petri nets. The model we consider is the untimed version of First-Order Hybrid Petri Nets: it combines a discrete Petri net and a continuous Petri net, the latter being a fluid version of a usual discrete Petri net. It is suggested that the decidability results should be pursued exploiting a hierarchy of models as it has been done in the framework of Hybrid Automata. In this paper we define the class of Single-Rate Hybrid Petri Nets: the continuous dynamics of these nets is such that the vector of the marking derivatives of the continuous places is constant but for a scalar factor. This class of nets can be seen as the counterpart of timed automata with skewed clocks. We prove that the reachability problem for this class can be reduced to the reachability problem of an equivalent discrete net and thus it is decidable
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
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