1,720,957 research outputs found
Assessing the safety benefit of automatic collision avoidance systems
No full textThroughout the last decade a number of advanced system concepts for improving safety, efficiency, environmental compatibility and comfort of driving have emerged. One of these, Automatic Collision Avoidance Systems (ACAS) aims to help drivers to avoid accidents by alerting them to a potential collision and initiating braking. This paper assesses the safety effects of ACAS by examining driver response during emergency braking situations.A series of emergency braking tests were undertaken on a test track. Six subjects (each with at least five years driving experience) were asked to follow a special ‘dummy’ vehicle and drive the TRG instrumented vehicle. The dummy vehicle, a lightweight trailer unit designed to withstand impacts safely, was then subjected to brake to a stop from three speed levels (60,45 and 30 mph) with decelerations which varied between 0.65g and 0.95g. The TRG instrumented vehicle enabled detailed information to be collected on driver responses such as relative speed, spacing distance, pedal movement, speed and deceleration levels.The data analysis has showed that drivers are likely to initiate their braking before the time to collision (TTC) reaches 4 seconds. Consequently, an autonomous ACAS with a 4 seconds TTC threshold would not give warning that could help drivers reducing their response time.Moreover, headway was found to be the main safety factor that ensures drivers would avoidcollision
The study of motorway operation using a microscopic simulation model
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DXN035538 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Findings on the approach process between vehicles on motorways
No full textOver the past 10 years there has been a growing body of research into modeling and describing driving behavior, particularly for situations that occur on motorways. This interest has arisen from the need to assess safety and capacity benefits that could be produced by changes to road design, operation, signage, and in-vehicle advanced transport telematics, such as collision warning (CW) or autonomous cruise control. For the most part these investigations have focused on "close" or "car" following, which describes the maintenance of a time- or distance-based following headway. However, often overlooked, and of equal importance, is the "approach" process, describing how a driver decelerates when approaching a slower vehicle. There are several competing theories of the behavioral basis underlying this process, including, for example, those based on time-to-collision or optic flow. There are, however, very few data against which such models can be assessed and systems designed. Presented are the results from an exploratory, instrumented vehicle study designed to assess approach mechanisms. The two key features of the process are explored: the circumstances under which driver deceleration is instigated, and the process governing the control of the deceleration itself. Finally, there is a brief assessment of the implications of these findings for the design of CW systems, in which realistic warnings may prove vital to their acceptance by the driving public.<br/
Motorway driver behaviour: studies on car following
No full textThis paper will report findings of an instrumented vehicle study aimed at assessing one element of driver behaviour, that of car following, on UK motorways. The paper (re-) calibrates one of the most successful of such models—the Action Point model—using dynamic time series data acquired from field tests with an instrumented vehicle. Probability distributions for a number of parameters from the Action Point model are produced and a number of modifications made in order to enhance its value for use in traffic flow and simulation models. Lastly typical headways are compared with existing studies in the area, finding that current headways are far lower than believed. The rationale behind the adoption of such short headways is examined
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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