1,721,110 research outputs found
A resource optimization framework for improving railway-highway grade crossing safety in Canada
No full textThis paper presents a new approach to address the problem of allocating federal resources and identifying upgrading projects for improving the safety of at-grade crossings in Canada. The proposed approach is unique in two key aspects. First, a risk-based network screening process is adopted to identify the priority sites for providing a justifiable basis for distributing the total budget at a regional level as well as narrowing the search space in the subject optimization step. Secondly, a mathematical programming approach is applied to formalize the resource allocation process with explicit consideration of the expected benefits - risk reduction and the costs of implementing the projects. This approach is expected to improve the process of identifying the optimal set of upgrading projects within each region, thus maximizing the return of investment. A full-scale case study from the Canadian crossing network is conducted to demonstrate the application of the proposed approach
Speed limit reduction in urban areas: A before-after study using Bayesian generalized mixed linear models
No full textIn fall 2009, a new speed limit of 40 km/h was introduced on local streets in Montreal (previous speed limit: 50 km/h). This paper proposes a methodology to efficiently estimate the effect of such reduction on speeding behaviors. We employ a full Bayes before-after approach, which overcomes the limitations of the empirical Bayes method. The proposed methodology allows for the analysis of speed data using hourly observations. Therefore, the entire daily profile of speed is considered. Furthermore, it accounts for the entire distribution of speed in contrast to the traditional approach of considering only a point estimate such as 85th percentile speed. Different reference speeds were used to examine variations in the treatment effectiveness in terms of speeding rate and frequency. In addition to comparing rates of vehicles exceeding reference speeds of 40 km/h and 50 km/h (speeding), we verified how the implemented treatment affected "excessive speeding" behaviors (exceeding 80 km/h). To model operating speeds, two Bayesian generalized mixed linear models were utilized. These models have the advantage of addressing the heterogeneity problem in observations and efficiently capturing potential intra-site correlations. A variety of site characteristics, temporal variables, and environmental factors were considered. The analyses indicated that variables such as lane width and night hour had an increasing effect on speeding. Conversely, roadside parking had a decreasing effect on speeding. One-way and lane width had an increasing effect on excessive speeding, whereas evening hour had a decreasing effect. This study concluded that although the treatment was effective with respect to speed references of 40 km/h and 50 km/h, its effectiveness was not significant with respect to excessive speeding-which carries a great risk to pedestrians and cyclists in urban areas. Therefore, caution must be taken in drawing conclusions about the effectiveness of speed limit reduction. This study also points out the importance of using a comparison group to capture underlying trends caused by unknown factors.</p
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
A Risk-Based Decision Support Framework for Railway-Highway Grade Crossing Closures
Full text linkReducing the risk of collisions between trains and vehicles at railway-highway grade crossings is a high priority safety strategy set by many governments and railway authorities. To achieve this goal, one of the main engineering approaches used is to permanently close some grade crossings. Although this approach can completely eliminate the collision risk at the grade crossings being closed, it could have a huge impact on the road traffic, resulting in a significant increase in travel time for road users. This can also lead to some secondary problems, such as increased trespassing risk. Thus, the problem of which crossings should be closed must be addressed with a careful consideration of all benefits and costs that could result from the closure. This research aims to develop a specific framework for determining the priority of grade crossing closure and develop models that can be used to quantify the safety benefit and the costs.
In this study, a risk-based framework is proposed, including a preliminary screening and a cost-benefit analysis module. In the preliminary screening step, all the crossings in the area of interest are first examined on the basis of a set of pre-established rules or criteria to remove those crossings that should definitely not be considered for closure due to their critical importance to the road traffic. This step yields a set of candidate crossings. All individual crossings in the candidate set are then involved in the cost-benefit analysis module. This module determines the expected safety benefit, travel time cost, and construction cost that could result from their closure. The safety benefit of closing a given crossing is estimated using a set of collision risk models for collision frequency and collision severity. These models are calibrated using the latest crossing inventory data and six-year long collision history data (2013-2018). To estimate the extra travel time cost that road users would experience due to the closure of a crossing, an accessibility analysis tool is created in a ArcMap to calculate the extra travel distance, using the spatial data of road and railway network. Lastly, the life-cycle benefit-cost ratios of all candidate crossings for closure can be calculated and used as a ranking criterion for determining their priority of closure. The application and rationality of the proposed framework are examined through a case study of three provinces in Canada
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
Development and Evaluation of Models and Algorithms for Locating RWIS Stations
No full textAccurate and timely information on road weather and surface conditions in winter seasons is a necessity for road authorities to optimize their winter maintenance operations and improve the safety and mobility of the traveling public. One of the primary tools for acquiring this information is road weather information systems (RWIS). While effective in providing real-time and near-future information on road weather and surface conditions, RWIS stations are costly to install and operate, and therefore can only be installed at a limited number of locations. To tackle this challenging task, this thesis develops various different approaches in an attempt to determine the optimal location and density over a regional highway network. The main research findings are summarized as follows.
First, a heuristic surrogate measure based method (SM) has been developed. Two types of location ranking criteria are proposed to formalize various processes utilized in the current practice, including weather and traffic related factors. Consideration of these two types of factors captures the needs to allocate RWIS stations to the areas with the most severe weather conditions and having the highest number of traveling public. A total of three location selection alternatives are generated and used to evaluate the current Ontario RWIS network. The findings indicate that the current RWIS network is able to provide a reasonably good coverage on all location criteria considered.
Second, a cost-benefit based method (CB) has been proposed to give an explicit account of the potential benefits of an RWIS network in its location and density planning. The approach has been constructed on a basis of a sensible assumption that a highway section covered by an RWIS station is more likely to receive better winter road maintenance (WRM) operations. A case study based on the current RWIS network in Northern Minnesota show that the highest projected 25-year net benefits are approximately $6.5 million with cost-benefit ratio of 3.5, given the network of 45 RWIS stations.
Third, a more comprehensive and innovative framework has been developed by using the weighted sum of average kriging variance of winter road weather conditions. Methodologically, the formulation of the RWIS location optimization problem is foundational with several unique features, including explicit consideration of spatial correlation of winter road weather conditions and high travel demand coverage. The optimization problem is then formulated by taking into account the dual criteria representing the value of RWIS information for spatial inferences and travel demand distribution. The spatial simulated annealing (SSA) algorithm was employed to solve the combinatorial optimization problem ensuring convergence. A case study based on four study regions covering one Canadian province (Ontario), and three US states (Utah, Minnesota, and Iowa) exemplified two distinct scenarios –redesign and expansion of the existing RWIS network. The findings indicate that the method developed is very effective in evaluating the existing network and delineating new site locations.
Additional analyses have been conducted to determine the spatial continuity of road weather conditions and its relation to the desirable RWIS density based on the case study results of the four study areas. Road surface temperature (RST) was used as a variable of interest, and its spatial structure for each region was quantified and modelled via semivariogram. The findings suggest that there is a strong dependency between the RWIS density and the autocorrelation range - the regions with less varied topography tend to have a longer spatial correlation range than the region with more varied topography.
The approaches proposed and developed in this thesis provide alternative ways of incorporating key road weather, traffic, and maintenance factors into the planning of an RWIS network in a region. Decision on which alternative to use depends on availability of data and resources. Nevertheless, all approaches can be conveniently implemented for real-world applications
- …
