1,721,002 research outputs found
Urban transport planning and energy resources: Electric vehicle routing with reliable link travel times
Full text linkThe rise of new types of vehicles, as the electrical vehicles (EVs), requires defining new models for transport simulation and design, both for freight and for passengers. This paper focuses on freight transport on the land side and it is in the area of the smart city where transport, energy and information and communications technology sectors are considered. This paper focuses on the transport sector and, in particular, the formulation of a vehicle routing problem is considered. The adopted approach considers three aspects: reliable travel time, path generation and best route design for electric vehicles. A possible formulation for a vehicle routing problem with time windows is reported, considering a specific constraint for electric vehicles. The main results obtained in some case studies are reported
Optimising Waiting at Nodes in Time-Dependent Networks: Cost Functions and Applications
No full textIn this paper, the relationship between waiting at nodes and the path cost in a transport network is analysed. An exact solution algorithm for generating the shortest path with optimal waiting at the nodes is proposed. The general case is examined, considering a time-dependent network (time influences the cost). To develop a full application, the algorithm is applied in the case of a vehicle routing problem on a real network. © 2012 Springer Science+Business Media, LLC
Una metodologia per la simulazione dell'assegnazione in sistemi di trasporto pubblico: applicazione ad un caso reale
No full textFor representing transit system two approaches can be used: line approach where all runs belonging to the same line are simulated in a single infrastructure line; run approach where the single runs are explicitly simulated.
Assignment models simulate how origin-destination demand flows affect link flows and resulting performances. Traffic assignment models in transit system are generally made up by two different approaches: with optimal strategy approach for high frequency system or strategic level and considering line approach for supply; with schedule-based strategy approach for low frequency system or operative and tactical level and considering run approach for supply.
In this paper the schedule-based strategy approach for low frequency system and the optimal-strategy approach are applied and compared in the extra-urban supply system of Reggio Calabria department. In the department there are about 576000 inhabitants and the supply has 1363 runs a day. The results obtained are discussed and are used for evaluate services integration and costs and revenues.
This paper is developed into the project PRIN “Linee guida per la programmazione dei servizi di trasporto pubblico locale” (prot. min. MM08471228) and continues a work presented at European Transport Conference 2002 in Cambridge
The multicriteria road network design problem in an urban area
No full textIn this paper, urban network design is analysed through a heuristic multi-criteria technique based on genetic algorithms. Both network layout and link capacity (link layout and traffic lights) are optimised. Different optimisation criteria are included for users, non-users and public system managers. Demand is considered elastic with respect to mode choice; both morning and afternoon peak periods are taken into account. In addition, choice of parking location is simulated. The procedure is applied to a test and to a real transportation system
Calibration of generalized cost models for road freight vehicles within an intermodal chain: an experimental application in Italy
No full textIn Italy an homogeneous modelling system for the analysis of freight transport on road and on other transport modality was developed. The incidence knowledge on freight transport time of different components is fundamental in many economics sectors.
In literature different cost-flow models are specified and calibrated to calculate the travel time for road freight transport. The models are different in relation to several aspects: calibration, adopted attributes, estimate of travel time, geographic area of reference, data surveys. This determines the effectiveness in term of explanation capacity and statistics reproducibility, with a low level of reciprocal compatibility, therefore of validity in term of modelling system.
For travel time the different approaches met in literature are in relation to the calibration relative to the links or to the OD pairs.
Link cost functions are calibrated in order to define the relation between the link flow or density and link cost or speed. If we define a road link, on which we do the measures, we want to calibrate using measured link costs and measured link flows, the parameters that permit to correct the link cost functions. The parameters can be calibrated in aggregated way for each road category or in disaggregated way for each road link.
In the OD pairs calibration the attention is on the path cost. In this case the cost in several OD pairs is measured and after the calibration of link cost function belonging to the paths are developed. Also in this case the calibration can be aggregated or disaggregated.
This paper is focused on the calibration in the OD pair and the link cost functions for road freight trucks are specified and calibrated for different categories. Three main categories are individuated: freeways, extra-urban roads and other types.
The dataset counts on about 40,000 interviews to truck drivers in the port of Messina. In fact, the truck trips from Sicily to other destination outside the island must cross the Straights of Messina. Data includes also departure locality and time, arrive time to the port of Messina. In this way we obtained the real (measured) time and cost on the paths. The estimation of cost-flow models for each category of links that compose the OD paths is done.
The work was developed inside a national program of research SINAVE (SIstema di NAvigazione VEloce - System of Fast Navigation) in which an innovative system of freight is investigated. The project wants to give, by the acquisition and adaptation of specific knowledge, innovative technology solutions for the sea transport system, with particular attention on South-North sea freight transport in competition with road transport
Bayesian Disaggregate and Aggregate Calibration of Path Logit Choice Models
No full textIn transport demand analysis, the calibration of a model means estimation of its (endogenous) parameters from observed data with an inference statistical estimator. Indeed, these considerations apply to any choice behaviour model, such as those derived from Random Utility Theory or any other choice modelling theory. Calibration of choice models can be carried out from disaggregate vs. aggregate data, while inference statistical estimators can be specified through Bayesian vs. Classic (or Frequentist) approaches. In this paper, the resulting Bayesian or Classic disaggregate or aggregate calibration methods are discussed, analysed in detail, and compared from the mathematical point of view. These methods are applied to calibrate Logit choice models for describing path choice behaviour at national scale on a small sample. The Logit choice model can be derived from Random Utility Theory (or be considered an instance of the Bradley-Terry model). Path choice set definition is also discussed, and specialised indicators are used for result comparison. The main contributions of this study concern the use of two different estimation approaches, Bayesian vs. Classic, adopting and introducing some indicators of goodness of estimation. The results of this work, relating to the sample of users adopted, show that the Bayesian approach provides a better estimate than the Classic approach because the calibrated parameters are more stable, the specific constants of the alternatives decrease, and the resulting models show better values of clearly right indicator
Initial results of theoretical and experimental research concerning road traffic flows analysis
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