1,720,964 research outputs found
Estimating and exploiting the capacity of urban street networks
Full text linkThe paper deals with the problem of estimating and exploiting traffic capacity of different road elements (link, nodes, network) and presents the results obtained by performing a systematic investigation of the role that the parameters of a microscopic simulation model play on the macroscopic representation of different road elements. An analysis of traffic parameters has been performed using a microsimulation software package to identify the most important parameters affecting the arterial capacity and to calibrate driver's behavior models through macroscopic traffic observations
Coherence analysis of road safe speed and driving behaviour from floating car data
No full textIn the Intelligent Transportation Systems, integration of different components of the classical driver-vehicleinfrastructure system is supported by advances in technology and communications. This study presents a general road safety analysis framework that exploits different types of data on traffic, geometry, and accidents to develop a Road Safety Analysis Center and an on-board Road Safety Driver Advisory. The Road Safety Analysis Center considers different sources of data: accident inventories, road geometry, and floating car data, which reveal drivers' behavior. Floating car data are also exploited to derive mathematically the longitudinal parameters of ancient roads, which are crucial to estimate safety conditions in curves. The critical points of the network are revealed by an aggregate analysis of accidents distribution on the roads, while the drivers' behaviour is addressed on a disaggregated level, by the evaluation of speeds distributions with a dense spatial detail. The comparison between speeds distributions, safety conditions, and accident occurrence is useful to individuate the portions of the network to be enforced with safety measures and support drivers with an advanced onboard speed advisory system. This methodology is applied to several extra-urban roads in the Latium region, Italy, to individuate roads with higher values of critical indices
Meta-heuristic aggregate calibration of transport models exploiting data collected in mobility
No full textThe wide diffusion of data collected in mobility led to an unprecedented amount of information about people's mobility behavior. While on one hand the availability of big data from multiple sources enables to calibrate complex models with a high number of parameters, on the other hand, the dimension of the problem increases, and computational efficiency becomes an important issue. The paper presents a general methodology for the aggregate calibration of transport system models that exploits data collected in mobility jointly with other data sources within a multi-step optimization procedure based on metaheuristic algorithms. The methodology is applied to two real large-scale case studies in two different contexts. The first concerns the aggregate calibration updating a national strategic 4-step demand model in use in a big European Country; the second deals with the calibration of link and node performance functions implemented in a traffic network model of a town of around 3 million inhabitants. The results demonstrate the effectiveness of the aggregate calibration methodology in significantly improving earlier models' estimations. The results also highlight that the errors are in the same order of magnitude as the intrinsic variation of the data collected in the field
Road Design Criteria and Capacity Estimation Based on Autonomous Vehicles Performances. First Results from the European C-Roads Platform and A22 Motorway
Full text linkSeveral European road operators and authorities joined the C-Roads Platform with the aim of harmonising the deployment activities of cooperative intelligent transport systems (C-ITS). C-ITS research is preliminary to future automated-driving vehicles. The current conventional highways were designed on traditional criteria and models specifically developed for traffic flows of manually guided vehicles. Thus, this article describes some new criteria for designing and monitoring road infrastructures on the basis of performance features of autonomous (or self-driving) vehicles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Toward the development of a hybrid approach to speed estimation in urban and rural areas
No full textObjective: Given the strong relationship between road accident and traffic speed, the evaluation and prediction of this latter have always been considered as a critical issue for road safety analysis and for the evaluation of road network safety improvements. Prediction models developed to date mainly focused on spot speed in a rural environment or on running speed in an urban one. Very few analyze the speed estimation in “transition” areas. The objective of this paper is to develop a generalized speed estimation model able to predict mean speed in urban, rural, and “transition” environment as a function of road layout characteristics. It is believed that the proposed estimation tool can be effectively employed by road engineers in the road safety design and retrofitting stage. Methods: The basic idea of the paper is to shed some light on this issue by making use of a hybrid estimation approach able to combine the information gathered from both previously mentioned models within a generalized speed adaptation framework that reflects road user behavior. The calibration and validation of the generalized estimation model have been carried out following a collection of Floating Car Data (FCD) on several candidate sites. Results: Preliminary results seem to indicate that the methodology proposed may be effective in estimating the spot speed in two-lane rural and urban arterials. Conclusions: FCD data can be useful to develop more efficient estimation models to better manage the safety of urban and rural roads
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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