Download or read book Over and Under dispersed Crash Data written by Yaotian Zou and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In traffic safety analysis, a large number of distributions have been proposed to analyze motor vehicle crashes. Among those distributions, the traditional Poisson and Negative Binomial (NB) distributions have been the most commonly used. Although the Poisson and NB models possess desirable statistical properties, their application on modeling motor vehicle crashes are associated with limitations. In practice, traffic crash data are often over-dispersed. On rare occasions, they have shown to be under-dispersed. The over-dispersed and under-dispersed data can lead to the inconsistent standard errors of parameter estimates using the traditional Poisson distribution. Although the NB has been found to be able to model over-dispersed data, it cannot handle under-dispersed data. Among those distributions proposed to handle over-dispersed and under-dispersed datasets, the Conway-Maxwell-Poisson (COM-Poisson) and double Poisson (DP) distributions are particularly noteworthy. The DP distribution and its generalized linear model (GLM) framework has seldom been investigated and applied since its first introduction 25 years ago. The objectives of this study are to: 1) examine the applicability of the DP distribution and its regression model for analyzing crash data characterized by over- and under-dispersion, and 2) compare the performances of the DP distribution and DP GLM with those of the COM-Poisson distribution and COM-Poisson GLM in terms of goodness-of-fit (GOF) and theoretical soundness. All the DP GLMs in this study were developed based on the approximate probability mass function (PMF) of the DP distribution. Based on the simulated data, it was found that the COM-Poisson distribution performed better than the DP distribution for all nine mean-dispersion scenarios and that the DP distribution worked better for high mean scenarios independent of the type of dispersion. Using two over-dispersed empirical datasets, the results demonstrated that the DP GLM fitted the over-dispersed data almost the same as the NB model and COM-Poisson GLM. With the use of the under-dispersed empirical crash data, it was found that the overall performance of the DP GLM was much better than that of the COM-Poisson GLM in handling the under-dispersed crash data. Furthermore, it was found that the mathematics to manipulate the DP GLM was much easier than for the COM-Poisson GLM and that the DP GLM always gave smaller standard errors for the estimated coefficients.

Download or read book Examining the Application of Conway Maxwell Poisson Models for Analyzing Traffic Crash Data written by Srinivas Reddy Geedipally and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Statistical models have been very popular for estimating the performance of highway safety improvement programs which are intended to reduce motor vehicle crashes. The traditional Poisson and Poisson-gamma (negative binomial) models are the most popular probabilistic models used by transportation safety analysts for analyzing traffic crash data. The Poisson-gamma model is usually preferred over traditional Poisson model since crash data usually exhibit over-dispersion. Although the Poisson-gamma model is popular in traffic safety analysis, this model has limitations particularly when crash data are characterized by small sample size and low sample mean values. Also, researchers have found that the Poisson-gamma model has difficulties in handling under-dispersed crash data. The primary objective of this research is to evaluate the performance of the Conway-Maxwell-Poisson (COM-Poisson) model for various situations and to examine its application for analyzing traffic crash datasets exhibiting over- and under-dispersion. This study makes use of various simulated and observed crash datasets for accomplishing the objectives of this research. Using a simulation study, it was found that the COM-Poisson model can handle under-, equi- and over-dispersed datasets with different mean values, although the credible intervals are found to be wider for low sample mean values. The computational burden of its implementation is also not prohibitive. Using intersection crash data collected in Toronto and segment crash data collected in Texas, the results show that COM-Poisson models perform as well as Poisson-gamma models in terms of goodness-of-fit statistics and predictive performance. With the use of crash data collected at railway-highway crossings in South Korea, several COM-Poisson models were estimated and it was found that the COM-Poisson model can handle crash data when the modeling output shows signs of under-dispersion. The results also show that the COM-Poisson model provides better statistical performance than the gamma probability and traditional Poisson models. Furthermore, it was found that the COM-Poisson model has limitations similar to that of the Poisson-gamma model when handling data with low sample mean and small sample size. Despite its limitations for low sample mean values for over-dispersed datasets, the COM-Poisson is still a flexible method for analyzing crash data.

Download or read book Statistical and Econometric Methods for Transportation Data Analysis Second Edition written by Simon P. Washington and published by CRC Press. This book was released on 2010-12-02 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt: The complexity, diversity, and random nature of transportation problems necessitates a broad analytical toolbox. Describing tools commonly used in the field, Statistical and Econometric Methods for Transportation Data Analysis, Second Edition provides an understanding of a broad range of analytical tools required to solve transportation problems. It includes a wide breadth of examples and case studies covering applications in various aspects of transportation planning, engineering, safety, and economics. After a solid refresher on statistical fundamentals, the book focuses on continuous dependent variable models and count and discrete dependent variable models. Along with an entirely new section on other statistical methods, this edition offers a wealth of new material. New to the Second Edition A subsection on Tobit and censored regressions An explicit treatment of frequency domain time series analysis, including Fourier and wavelets analysis methods New chapter that presents logistic regression commonly used to model binary outcomes New chapter on ordered probability models New chapters on random-parameter models and Bayesian statistical modeling New examples and data sets Each chapter clearly presents fundamental concepts and principles and includes numerous references for those seeking additional technical details and applications. To reinforce a practical understanding of the modeling techniques, the data sets used in the text are offered on the book’s CRC Press web page. PowerPoint and Word presentations for each chapter are also available for download.

Download or read book Safe Mobility written by Dominique Lord and published by Emerald Group Publishing. This book was released on 2018-04-18 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book increases the level of knowledge on road safety contexts, issues and challenges; shares what can currently be done to address the variety of issues; and points to what needs to be done to make further gains in road safety.

Download or read book Highway Safety Analytics and Modeling written by Dominique Lord and published by Elsevier. This book was released on 2021-02-27 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Highway Safety Analytics and Modeling comprehensively covers the key elements needed to make effective transportation engineering and policy decisions based on highway safety data analysis in a single. reference. The book includes all aspects of the decision-making process, from collecting and assembling data to developing models and evaluating analysis results. It discusses the challenges of working with crash and naturalistic data, identifies problems and proposes well-researched methods to solve them. Finally, the book examines the nuances associated with safety data analysis and shows how to best use the information to develop countermeasures, policies, and programs to reduce the frequency and severity of traffic crashes. Complements the Highway Safety Manual by the American Association of State Highway and Transportation Officials Provides examples and case studies for most models and methods Includes learning aids such as online data, examples and solutions to problems

Download or read book Foundations of Linear and Generalized Linear Models written by Alan Agresti and published by John Wiley & Sons. This book was released on 2015-02-23 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: A valuable overview of the most important ideas and results in statistical modeling Written by a highly-experienced author, Foundations of Linear and Generalized Linear Models is a clear and comprehensive guide to the key concepts and results of linearstatistical models. The book presents a broad, in-depth overview of the most commonly usedstatistical models by discussing the theory underlying the models, R software applications,and examples with crafted models to elucidate key ideas and promote practical modelbuilding. The book begins by illustrating the fundamentals of linear models, such as how the model-fitting projects the data onto a model vector subspace and how orthogonal decompositions of the data yield information about the effects of explanatory variables. Subsequently, the book covers the most popular generalized linear models, which include binomial and multinomial logistic regression for categorical data, and Poisson and negative binomial loglinear models for count data. Focusing on the theoretical underpinnings of these models, Foundations ofLinear and Generalized Linear Models also features: An introduction to quasi-likelihood methods that require weaker distributional assumptions, such as generalized estimating equation methods An overview of linear mixed models and generalized linear mixed models with random effects for clustered correlated data, Bayesian modeling, and extensions to handle problematic cases such as high dimensional problems Numerous examples that use R software for all text data analyses More than 400 exercises for readers to practice and extend the theory, methods, and data analysis A supplementary website with datasets for the examples and exercises An invaluable textbook for upper-undergraduate and graduate-level students in statistics and biostatistics courses, Foundations of Linear and Generalized Linear Models is also an excellent reference for practicing statisticians and biostatisticians, as well as anyone who is interested in learning about the most important statistical models for analyzing data.

Download or read book Application of Finite Mixture Models for Vehicle Crash Data Analysis written by Byung Jung Park and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing sound or reliable statistical models for analyzing vehicle crashes is very important in highway safety studies. A difficulty arises when crash data exhibit overdispersion. Over-dispersion caused by unobserved heterogeneity is a serious problem and has been addressed in a variety ways within the negative binomial (NB) modeling framework. However, the true factors that affect heterogeneity are often unknown to researchers, and failure to accommodate such heterogeneity in the model can undermine the validity of the empirical results. Given the limitations of the NB regression model for addressing over-dispersion of crash data due to heterogeneity, this research examined an alternative model formulation that could be used for capturing heterogeneity through the use of finite mixture regression models. A Finite mixture of Poisson or NB regression models is especially useful when the count data were generated from a heterogeneous population. To evaluate these models, Poisson and NB mixture models were estimated using both simulated and empirical crash datasets, and the results were compared to those from a single NB regression model. For model parameter estimation, a Bayesian approach was adopted, since it provides much richer inference than the maximum likelihood approach. Using simulated datasets, it was shown that the single NB model is biased if the underlying cause of heterogeneity is due to the existence of multiple counting processes. The implications could be poor prediction performance and poor interpretation. Using two empirical datasets, the results demonstrated that a two-component finite mixture of NB regression models (FMNB-2) was quite enough to characterize the uncertainty about the crash occurrence, and it provided more opportunities for interpretation of the dataset which are not available from the standard NB model. Based on the models from the empirical dataset (i.e., FMNB-2 and NB models), their relative performances were also examined in terms of hotspot identification and accident modification factors. Finally, using a simulation study, bias properties of the posterior summary statistics for dispersion parameters in FMNB-2 model were characterized, and the guidelines on the choice of priors and the summary statistics to use were presented for different sample sizes and sample-mean values.

Download or read book International Encyclopedia of Transportation written by and published by Elsevier. This book was released on 2021-05-13 with total page 4418 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an increasingly globalised world, despite reductions in costs and time, transportation has become even more important as a facilitator of economic and human interaction; this is reflected in technical advances in transportation systems, increasing interest in how transportation interacts with society and the need to provide novel approaches to understanding its impacts. This has become particularly acute with the impact that Covid-19 has had on transportation across the world, at local, national and international levels. Encyclopedia of Transportation, Seven Volume Set - containing almost 600 articles - brings a cross-cutting and integrated approach to all aspects of transportation from a variety of interdisciplinary fields including engineering, operations research, economics, geography and sociology in order to understand the changes taking place. Emphasising the interaction between these different aspects of research, it offers new solutions to modern-day problems related to transportation. Each of its nine sections is based around familiar themes, but brings together the views of experts from different disciplinary perspectives. Each section is edited by a subject expert who has commissioned articles from a range of authors representing different disciplines, different parts of the world and different social perspectives. The nine sections are structured around the following themes: Transport Modes; Freight Transport and Logistics; Transport Safety and Security; Transport Economics; Traffic Management; Transport Modelling and Data Management; Transport Policy and Planning; Transport Psychology; Sustainability and Health Issues in Transportation. Some articles provide a technical introduction to a topic whilst others provide a bridge between topics or a more future-oriented view of new research areas or challenges. The end result is a reference work that offers researchers and practitioners new approaches, new ways of thinking and novel solutions to problems. All-encompassing and expertly authored, this outstanding reference work will be essential reading for all students and researchers interested in transportation and its global impact in what is a very uncertain world. Provides a forward looking and integrated approach to transportation Updated with future technological impacts, such as self-driving vehicles, cyber-physical systems and big data analytics Includes comprehensive coverage Presents a worldwide approach, including sets of comparative studies and applications

Download or read book Examing the Poisson Weibull Generalized Model for Analyzing Crash Data written by Lingzi Cheng and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last 20 to 30 years, there have been a significant number of statistical methods proposed for analyzing crash data. Traffic crashes are characterized as random and independent discrete non-negative events. Crash data have often been shown to exhibit over-dispersion. Therefore, the Negative Binomial (NB) is the preferred and widely used model to analyze this kind of data. Although NB model is very popular in traffic safety area, it still has limitations modeling crash data especially when crash data are characterized by low sample mean and small sample size. The main research objective of this thesis is to develop a new statistical method namely, Poisson-Weibull (PW) Generalized Linear Model (GLM) to analyze vehicle crash data and to evaluate its modeling performance at different dispersion levels. This study makes use of both simulated and observed data for accomplishing the research objectives. The PW model is the mixture of Poisson and Weibull distributions. In this research, the statistical characteristics of the PW model were well defined and the parameters were estimated using a Bayesian approach. The PW model was initially evaluated using a series of simulated data for different dispersion levels. It was found that the PW model was able to reproduce and capture the true parameter values with high accuracy. After the initial analysis using the simulated data, the PW GLM was applied to two observed datasets and compared with the NB model. The goodness-of-fit (GOF) tests and model comparisons showed that the PW model performed as well as the NB model. Therefore, the PW model can be considered as an innovative and promising alternative for analyzing crash data.

Download or read book Modeling Count Data written by Joseph M. Hilbe and published by Cambridge University Press. This book was released on 2014-07-21 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides guidelines and fully worked examples of how to select, construct, interpret and evaluate the full range of count models.

Download or read book The Conway Maxwell Poisson Distribution written by Kimberly F. Sellers and published by Cambridge University Press. This book was released on 2023-02-28 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the Poisson distribution is a classical statistical model for count data, the distributional model hinges on the constraining property that its mean equal its variance. This text instead introduces the Conway-Maxwell-Poisson distribution and motivates its use in developing flexible statistical methods based on its distributional form. This two-parameter model not only contains the Poisson distribution as a special case but, in its ability to account for data over- or under-dispersion, encompasses both the geometric and Bernoulli distributions. The resulting statistical methods serve in a multitude of ways, from an exploratory data analysis tool, to a flexible modeling impetus for varied statistical methods involving count data. The first comprehensive reference on the subject, this text contains numerous illustrative examples demonstrating R code and output. It is essential reading for academics in statistics and data science, as well as quantitative researchers and data analysts in economics, biostatistics and other applied disciplines.

Download or read book Negative Binomial Generalized Exponential Distribution written by Prathyusha Vangala and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modelling crash data has been an integral part of the research done in highway safety. Different tools have been suggested by researchers to analyze crash data. One such tool, which was recently proposed, is the Negative Binomial Generalized Exponential (NB-GE) distribution. As the name suggests, it is a combination of Negative Binomial and Generalized Exponential distribution. This distribution has three parameters and can handle over-dispersed crash data which are characterized by a large number of zeros and/or long tail. This research seeks to develop a generalized linear model (GLM) for NB-GE distribution and discuss its applications in crash data analysis. The NB-GE GLM was applied to two over-dispersed crash datasets and its performance was compared to Negative Binomial-Lindley (NB-L) and Negative Binomial (NB) models using various statistical measures. It was found that NB-GE performs almost as well as NB-L model and performs much better than the NB model. This research tried to determine the percentage of zeroes and the dispersion in the dataset where the NB-GE model is recommended over the NB model for ranking sites. Datasets were simulated for different scenarios. It was found that for high dispersion the NB-GE model performs better than the NB model when the percentage of zero counts in the dataset is greater than 80%. When dataset has lower than 80% zeroes then NB model and NB-GE model perform similarly. Hence for lower percentages NB model would be preferred as it is simpler and easier to use. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155124

Download or read book Introduction to Data Analysis with R for Forensic Scientists written by James Michael Curran and published by CRC Press. This book was released on 2010-07-30 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Statistical methods provide a logical, coherent framework in which data from experimental science can be analyzed. However, many researchers lack the statistical skills or resources that would allow them to explore their data to its full potential. Introduction to Data Analysis with R for Forensic Sciences minimizes theory and mathematics and focus

Download or read book Urban Transport XIX written by C. A. Brebbia and published by WIT Press. This book was released on 2013-05-01 with total page 861 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the papers presented at the nineteenth annual International Conference on Urban Transport and the Environment. The papers cover research on how to minimise ecological and environmental impacts from urban transportation systems, make them sustainable, and use them to improve the socio-economic fabric of the city. Papers also address the concerns about the safety, security and efficiency of the systems.Topics covered include: Urban transport planning and Management; Transportation demand analysis; Traffic integration and control; Intelligent transport systems; Transport modelling and simulation; Land use and transport integration; Public transport systems; Environmental and ecological aspects; Air and noise pollution; Safety and security; Energy and transport fuels; Economic and social impact; and Advanced transport systems.

Download or read book Regression Models for Categorical and Limited Dependent Variables written by J. Scott Long and published by SAGE. This book was released on 1997-01-09 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: Evaluates the most useful models for categorical and limited dependent variables (CLDVs), emphasizing the links among models and applying common methods of derivation, interpretation, and testing. The author also explains how models relate to linear regression models whenever possible. Annotation c.

Download or read book Vehicle Crash Mechanics written by Matthew Huang and published by CRC Press. This book was released on 2002-06-19 with total page 499 pages. Available in PDF, EPUB and Kindle. Book excerpt: Governed by strict regulations and the intricate balance of complex interactions among variables, the application of mechanics to vehicle crashworthiness is not a simple task. It demands a solid understanding of the fundamentals, careful analysis, and practical knowledge of the tools and techniques of that analysis. Vehicle Crash Mechanics s

Download or read book Generalized Poisson Distributions written by P. C. Consul and published by CRC Press. This book was released on 1988-12-22 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents 28 bar diagrams that illustrate the versatility of the generalized Poisson model and discusses stochastic processes leading to the generalized Poisson distribution. Examines theoretical properties that vary in difficulty, includes proofs for numerous theorems, explores confidence intervals