161,796 research outputs found
DERIVAZIONE DEI MODELLI PREVISIONALI PER LE ROTATORIE URBANE. UN CASO STUDIO,
No full textCome è noto, i modelli previsionali d’incidentalità (in campo internazionale conosciuti come Safety Performance Functions) vengono ormai da tempo impiegati nelle valutazioni di sicurezza; ad essi è affidato il compito di condensare le conoscenze pregresse sulla sicurezza di entità (tronchi stradali, intersezioni, etc.) simili a quelli in considerazione.
Quando integrati in una procedura di stima empirico-bayesiana, i modelli previsionali d’incidentalità concorrono alla correzione della distorsione dovuta alla regressione verso la media ed all’accrescimento della precisione della stima.
Nella presente memoria viene presentato un esempio di determinazione di tali modelli per il caso di rotatorie urbane.
Attraverso lo stesso esempio, si intende mostrare l’opportunità di prendere in considerazione la correlazione temporale dei dati, in conseguenza della quale l’ipotesi di indipendenza che autorizza l’impiego di modelli lineari generalizzati (GLM) cade in difetto.
Contemporaneamente, si intende mostrare come uno sforzo addizionale che tenga conto della vera struttura di correlazione dei dati possa essere compensato da una migliore precisione nella stima dei parametri del modello
Improving Reliability of Road Safety Estimates with High Correlated Accidents Count Data
No full textEstimating pollutant emissions based on speed profiles at urban roundabouts: A pilot study
No full textThe paper describes the pilot study conducted to assess the feasibility of the empirical approach utilizing vehicle trajectory data from a smartphone app and the Vehicle-Specific Power methodology to estimate pollutant emissions at urban roundabouts. The goal of this research phase is to acquire instantaneous speed data from a sample of six roundabouts located in the road network of the City of Palermo, Italy, and quantify emissions generated by the test vehicle through the examined roundabouts. For the case studies of roundabouts acceleration events in the circulating and exiting areas contributed to about 25% of the emissions for a given speed profile. More in general, the results from this research shed lights for further opportunities to examine infrastructural scenarios when decision makers require to assess changes in the design or operation of urban transportation systems
Improving reliability of road safety estimates based on high correlated accidents counts
No full textCalibrating a safety performance function (SPF) with many years of accident data creates a temporal correlation that traditional model calibration procedures cannot deal with. It is well known that generalized estimating equations (GEE) models are able to incorporate trends into accident data and thus overcome difficulties in accounting for correlation; the usual application of GEEs to safety analysis uses robust (or sandwich) estimates of regression coefficients under the independence hypothesis for the working correlation matrix. This practice is justified by the robustness of the GEE procedure against misspecification of the response correlation structure. Nevertheless, with this method, one has to renounce the entirety of the advantages of GEE estimates, and - especially when correlation within the subject is high - significant losses in efficiency and misleading conclusions in model interpretation can occur. In such a case, losses in efficiency of the estimates will be transferred to the reliability of the final safety estimation, for example, by the empirical Bayes method. On the basis of these considerations, the main idea of this study is that, in safety modeling, additional effort to obtain the true data correlation structure will result in better precision in the estimation of SPF parameters. An example to illustrate the methodological aspects of the proposed approach is included
Managing Greenhouse Gas Emissions for Airport Inventories: An Overview
No full textFor some years now, problems relating to gas emissions that affect climate and result from human activities have
assumed a global dimension of large importance. The climate is, indeed, influenced by the concentrations of
some pollutants in the atmosphere; these pollutants trap the long wave radiation emitted by the Earth and alter
the energy balance, causing an accentuation of the natural greenhouse effect. In this view an inventory of
greenhouse gases can become the benchmark against which to measure the achievement of quantitative targets
set at the political level in the fight against climate change. Contrary to a general inventory of emissions related
with air quality objectives and local effects of pollutants, a greenhouse gas inventory does not set objectives
purely local, but it directs efforts towards the quantification of the liability of an area compared to a global
problem as climate change, also in view of possible improvements. The inventory is thus the reference for the
evaluation of pre-and post-operam actions aimed at reducing the greenhouse effect, as well as for their
monitoring over time. The article in an overview of the main issues of air pollution associated to airport
operations and a review of the airport sources and components contributing to greenhouse gas emissions. After a
brief description of the most recent international and national standards and recommendations on this topic, the
article focuses on reasons for developing a greenhouse gas emission inventories and traces the essential elements
in the methodology to be followed by airport operators for preparing an airport-specific inventory of greenhouse
gas emissions. Methods for calculating emissions are also summarized and reviewed. Finally, the new references
to the environmental sustainability at airports, as well as the main measures to be taken to reduce emissions are
also identified and commented o
How to derive the analytical capacity model for not-conventional urban roundabouts
No full textThe inapplicability of current methods for analyzing operations of urban not-conventional roundabouts (i.e. not referable to standard schemes) hampers seriously the assessment of their operational performances. Moreover, local constraints and the road network structure have produced lots of geometric layouts that make hard to propose an only framework to explain performances of not-conventional roundabouts. Also for these intersections it is hoped to have scientifically based methods to analyze operations with a proper reliability. Starting from these considerations, the paper shows the conceptual path followed to analyze operations at not-conventional roundabouts along an arterial of Palermo City. The examined intersections have suggested a theoretic-experimental approach that balances the need both to match field observations and to have a general criterion to determine performances. A case study application allows to explain how to derive the analytical capacity model from field data. Moreover the comparison of results to those derived by models for conventional schemes inform us about the effect on capacity aroused by a more realistic operational pattern such as that observed at multilane-large-diameter roundabouts.The inapplicability of current methods for analyzing operations of urban not-conventional roundabouts (i.e. not referable to standard schemes) hampers seriously the assessment of their operational performances. Moreover, local constraints and the road network structure have produced lots of geometric layouts that make hard to propose an only framework to explain performances of not-conventional roundabouts. Also for these intersections it is hoped to have scientifically based methods to analyze operations with a proper reliability. Starting from these considerations, the paper shows the conceptual path followed to analyze operations at not-conventional roundabouts along an arterial of Palermo City. The examined intersections have suggested a theoretic-experimental approach that balances the need both to match field observations and to have a general criterion to determine performances. A case study application allows to explain how to derive the analytical capacity model from field data. Moreover the comparison of results to those derived by models for conventional schemes inform us about the effect on capacity aroused by a more realistic operational pattern such as that observed at multilane-large-diameter roundabouts
La "proprieta commerciale" nella dinamica dell\u27azienda
No full textMilano : Giuffre, 1966
https://galileodiscovery.unipd.it/discovery/fulldisplay?context=L&vid=39UPD_INST:VU1&search_scope=MyInst_and_CI&tab=Everything&docid=alma99000287865020604
Le societa commerciali in rapporto al giudizio civile
No full textMilano : Giuffre, 1962
https://galileodiscovery.unipd.it/discovery/fulldisplay?context=L&vid=39UPD_INST:VU1&search_scope=MyInst_and_CI&tab=Everything&docid=alma99000277509020604
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