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Development Of Safety Performance Functions For Two Lane Roads Maintained By The Virginia Department Of Transportation
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Book Synopsis Development of Safety Performance Functions for Two-lane Roads Maintained by the Virginia Department of Transportation by : Nicholas J. Garber
Download or read book Development of Safety Performance Functions for Two-lane Roads Maintained by the Virginia Department of Transportation written by Nicholas J. Garber and published by . This book was released on 2010 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, significant effort and money have been invested to enhance highway safety. As available funds decrease, the allocation of resources for safety improvement projects must yield the maximum possible return on investment. Identifying highway locations that have the highest potential for crash reduction with the implementation of effective safety countermeasures is therefore an important first step in achieving the maximum return on safety investment. This study was undertaken to develop safety performance functions (SPFs) for use in Virginia in conjunction with SafetyAnalyst, a computerized analytical tool that can be used for prioritizing safety projects. A safety performance function is a mathematical relationship (model) between frequency of crashes by severity and the most significant causal factors of crashes for a specific type of road. Although the SafetyAnalyst User's Manual recommends four SPFs for two-lane segments, these SPFs were developed using data from Ohio. Because the transferability of these SPFs to other states could not be guaranteed by the developers of the four recommended SPFs, it is necessary to calibrate or develop valid SPFs for each state using appropriate data from the state. In this study, annual average daily traffic (AADT) was used as the most significant causal factor for crashes, emulating the SPFs currently suggested by Safety Analyst. SPFs for two-lane roads in Virginia were developed for total crashes and combined fatal plus injury crashes through generalized linear modeling using a negative binomial distribution for the crashes. Models were developed for urban and rural areas separately, and in order to account for the different topographies in Virginia, SPFs were also separately developed for three regions in Virginia. A total of 139,635 sites were identified for use in this study. Each site is a segment of a rural or urban two-lane road without an intersection for which AADT data were available for the years 2003 through 2007 inclusive and no change in facility type had occurred over that period. A comparative analysis based on the Freeman-Tukey R2 coefficient was then conducted between the relevant Ohio SPFs suggested for use in the SafetyAnalyst User's Manual and those specifically developed in this study for Virginia to determine which set of models better fit the Virginia data. In general, the results indicated that the SPFs specifically developed for Virginia fit the Virginia data better. The final step in this methodology was to illustrate the value of SPFs developed through an analysis of sample sites and the need of the sites for safety improvement based on SPFs as compared to crash rates. The results indicated that prioritization using the empirical Bayes method that incorporates the SPFs resulted in a higher potential for reduction in crashes than did prioritization using crash rates. The effective use of SafetyAnalyst will facilitate the identification of sites with a high potential for safety improvement, which, in turn, with the implementation of appropriate safety improvements, will result in a considerable reduction in crashes and their severity.
Book Synopsis Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia by : Hyun W. Cho
Download or read book Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia written by Hyun W. Cho and published by . This book was released on 2020 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: About 17,500 crashes per year occur on the more than 32,800 lane-miles of undivided two-lane rural roads maintained by the Virginia Department of Transportation (VDOT), and crash numbers are increasing. Roadway departure (RD) crashes comprise about 58% of crashes on these roads. Since these crashes are widely distributed across the state, determining how and where to focus limited highway safety resources through the deployment of low-cost, high-benefit systemic countermeasures is paramount to beginning to reduce the number of crashes on these roads. This purpose of this study was to develop a systemic safety improvement plan for RD crashes on two-lane rural roads using low-cost countermeasures. Segments that have the potential for safety improvement were selected using VDOT’s RD safety performance functions. Decision tree analysis was applied to perform a systemic classification of roadway characteristics that are correlated with RD problems. A list of countermeasures to deploy to target specific segments and patterns was developed based on the literature and input from VDOT staff. The countermeasures were intended to warn of curves ahead, delineate curves, and warn of lane/road departure. Before deployment, a study of the section by VDOT district traffic engineering staff is planned in order to finalize the safety improvement plan. The output of the study will be a safety improvement plan to deploy treatments systemically to two-lane rural roads as part of VDOT’s safety program.
Book Synopsis Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation by : Nicholas J. Garber
Download or read book Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation written by Nicholas J. Garber and published by . This book was released on 2010 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, significant effort and money have been invested through research and implemented safety projects to enhance highway safety in Virginia. However, there is still substantial room for improvement in both crash frequency and severity. As there are limits in the available funds for safety improvements, it is crucial that allocated resources for safety improvement be spent at highway locations that will result in the maximum safety benefits. In addition, intersection crashes play a significant role in the safety conditions in Virginia. For example, crashes at intersections in Virginia for the period 2003 through 2007 account for 43.8% of all crashes and 26% of fatal crashes. Therefore, identifying intersections for safety improvements that will give the highest potential for crash reduction when appropriate safety countermeasures are implemented will have a significant impact on the overall safety performance of roads in Virginia. The Federal Highway Administration (FHWA) has developed a procedure for identifying highway locations that have the highest potential for crash reduction (ITT Corporation, 2008). A critical component of this method is the use of safety performance functions (SPFs) to determine the potential for crash reductions at a location. An SPF is a mathematical relationship (model) between frequency of crashes by severity and the most significant causal factors on a specific highway. Although the SafetyAnalyst User's Manual presents several SPFs for intersections, these were developed using data from Minnesota. FHWA also suggested that if feasible, each state should develop its own SPFs based on crash and traffic volume data from the state, as the SPFs that are based on Minnesota data may not adequately represent the crash characteristics in all states. SPFs for intersections in Virginia were developed using the annual average daily traffic as the most significant causal factor, emulating the SPFs currently suggested by SafetyAnalyst. The SPFs were developed for both total crashes and combined fatal plus injury crashes through generalized linear modeling using a negative binomial distribution. Models were also developed for urban and rural intersections separately, and in order to account for the different topographies in Virginia, SPFs were also developed for three regions: Northern, Western, and Eastern. This report covers Phases I and II of the study, which includes urban and rural intersections maintained by VDOT. Statistical comparisons of the models based on Minnesota data with those based on the Virginia data showed that the specific models developed for Virginia fit the Virginia crash data better. The report recommends that VDOT's Traffic Engineering Division use the SPFs developed for Virginia and the specific regional SPFs suggested in this report to prioritize the locations in need of safety improvement.
Book Synopsis Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation by : Young-Jun Kweon
Download or read book Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation written by Young-Jun Kweon and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Virginia Department of Transportation (VDOT) adopted the software Safety Analyst as its highway safety management tool in 2009. One of the requirements for implementation of Safety Analyst is to have appropriate safety performance functions (SPFs) reflecting Virginia conditions. The purpose of this study was to develop such SPFs for multilane highway and freeway segments that could replace Safety Analyst's default SPFs. Five years (2004-2008) of data collected from 20,235 multilane highway segments and 2,905 directional freeway segments in Virginia were used in the development of the SPFs. Statewide SPFs were developed for 4 subtypes of multilane highway segments and 10 subtypes of freeway segments. VDOT district-group SPFs were developed for 4 subtypes of multilane highway segments. The default SPFs in Safety Analyst were found to be different than the developed Virginia SPFs with respect to their curve shapes, and, as a result, adjusting the default SPFs to Virginia conditions by calibration factors resulted in inaccurate crash predictions at low and high volumes of annual average daily traffic. Thus, the Virginia-specific statewide SPFs developed in this study should be used when implementing Safety Analyst in Virginia. Although the shapes of the multilane highway segment SPFs were found to vary across VDOT districts, incorporating variations through the creation of new subtypes was found to be inappropriate for the current version of Safety Analyst. As a consequence, district-group SPFs for the multilane highway segments cannot be implemented in Safety Analyst. However, all SPFs developed in this study, including district group SPFs, can be implemented without the use of Safety Analyst. Therefore, use of the statewide SPFs developed in this study is recommended when Safety Analyst can be used and use of the statewide or district-group SPFs developed in this study is recommended when implementation of Safety Analyst is not feasible.
Book Synopsis Development of Safety Performance Functions for Two-lane Roads in Virginia by : Phillip R. Haas
Download or read book Development of Safety Performance Functions for Two-lane Roads in Virginia written by Phillip R. Haas and published by . This book was released on 2009 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of Safety Performance Functions for Network Screening of Roadway Departure Crashes in Virginia by : Young-Jun Kweon
Download or read book Development of Safety Performance Functions for Network Screening of Roadway Departure Crashes in Virginia written by Young-Jun Kweon and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Roadway departure (RD) is recognized as one of the eight emphasis areas in the Virginia 2017-2021 Strategic Highway Safety Plan (SHSP), and the Virginia Department of Transportation (VDOT) currently uses counts of RD crashes to identify locations for RD safety improvement. However, identifying locations based on crash counts is subject to bias and inaccuracy, leading to ineffective or erroneous outcomes. The safety performance functions (SPFs) VDOT has been using for statewide network screening might be used for RD safety improvement, but this could lead to undesirable outcomes in that the current SPFs focus on all crash types and RD safety issues are believed to be different from those of other crash types. This study was designed to develop SPFs for statewide network screening for RD safety improvements to overcome this issue. RD SPFs were developed for 16 site types ranging from rural 2-lane segments to urban freeway segments with 8 or more lanes. It should be noted that crashes within 250 feet from an intersection are excluded according to VDOT's RD definition. Of the 96 RD SPFs (16 site types x 2 severity levels x 3 functional forms) initially investigated, 93 RD SPFs were successfully developed for RD network screening. One site type did not result in statistically significant RD SPFs for fatal and injury crashes, likely because of its small sample size. The study found that the RD SPFs vary in their functional forms of annual average daily traffic (AADT) across the site types. The logarithmic functional form of AADT, regarded as a standard for an SPF, is deemed suitable in general for a typical range of AADT. However, that form could be severely deviated from the true relationship in the data. The study also found that the functional forms of AADT vary by injury severity. The forms are generally similar between the two severity levels, yet there are some cases where the difference is substantial. Accordingly, the functional form of AADT in an SPF for RD crashes should be determined for each site type and by severity level (all RD crashes and fatal and injury RD crashes) separately whenever possible. Based on the findings, the study recommends that the RD SPFs developed in this study be incorporated in the current VDOT statewide network RD screening procedure. Specifically, the final RD SPFs determined by goodness of fit and prediction capability measures (Tables 11 and 12) are recommended for use. For some site types, more than one final SPF are provided, allowing VDOT to select the most appropriate one for network screening considering the practicality of implementing the RD SPFs. Development of separate SPFs by site type and by severity was desirable to avoid possible inaccurate outcomes of network screening.
Book Synopsis Roundabouts by : Lee August Rodegerdts
Download or read book Roundabouts written by Lee August Rodegerdts and published by Transportation Research Board. This book was released on 2010 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide - Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts. This report updates the U.S. Federal Highway Administration's Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.
Book Synopsis Longitudinal Data Analysis by : Donald Hedeker
Download or read book Longitudinal Data Analysis written by Donald Hedeker and published by John Wiley & Sons. This book was released on 2006-05-12 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: Longitudinal data analysis for biomedical and behavioral sciences This innovative book sets forth and describes methods for the analysis of longitudinaldata, emphasizing applications to problems in the biomedical and behavioral sciences. Reflecting the growing importance and use of longitudinal data across many areas of research, the text is designed to help users of statistics better analyze and understand this type of data. Much of the material from the book grew out of a course taught by Dr. Hedeker on longitudinal data analysis. The material is, therefore, thoroughly classroom tested and includes a number of features designed to help readers better understand and apply the material. Statistical procedures featured within the text include: * Repeated measures analysis of variance * Multivariate analysis of variance for repeated measures * Random-effects regression models (RRM) * Covariance-pattern models * Generalized-estimating equations (GEE) models * Generalizations of RRM and GEE for categorical outcomes Practical in their approach, the authors emphasize the applications of the methods, using real-world examples for illustration. Some syntax examples are provided, although the authors do not generally focus on software in this book. Several datasets and computer syntax examples are posted on this title's companion Web site. The authors intend to keep the syntax examples current as new versions of the software programs emerge. This text is designed for both undergraduate and graduate courses in longitudinal data analysis. Instructors can take advantage of overheads and additional course materials available online for adopters. Applied statisticians in biomedicine and the social sciences can also use the book as a convenient reference.
Download or read book Gravel Roads written by Ken Skorseth and published by . This book was released on 2000 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this manual is to provide clear and helpful information for maintaining gravel roads. Very little technical help is available to small agencies that are responsible for managing these roads. Gravel road maintenance has traditionally been "more of an art than a science" and very few formal standards exist. This manual contains guidelines to help answer the questions that arise concerning gravel road maintenance such as: What is enough surface crown? What is too much? What causes corrugation? The information is as nontechnical as possible without sacrificing clear guidelines and instructions on how to do the job right.
Book Synopsis Two-lane Rural Highways Safety Performance Functions by : Venky Shankar
Download or read book Two-lane Rural Highways Safety Performance Functions written by Venky Shankar and published by . This book was released on 2016 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of Safety Performance Functions for Intersections in Virginia by : Griselle Rivera
Download or read book Development of Safety Performance Functions for Intersections in Virginia written by Griselle Rivera and published by . This book was released on 2010 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of Safety Performance Functions for Undivided Rural Two-lane Roadways by : Paige Martz
Download or read book Development of Safety Performance Functions for Undivided Rural Two-lane Roadways written by Paige Martz and published by . This book was released on 2017 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the research was to develop a methodology for creating safety performance functions specific to the state of Wisconsin, using undivided rural two-lane roadways. The methodology was designed to complement the practices of Wisconsin Department of Transportation (WisDOT) and work with the database WisDOT uses. The considered variables included curve presence, lane width, right shoulder total width, right shoulder paved width, truck percent, international roughness index, and posted speed. Negative Binomial regression models were developed using a dataset of 7,911 segments. Cumulative residual plots identified significant points in the AADT range where the SPFs could be split into two. Results show using two models, split by AADT at 7,500 vehicles per day (vpd) for all crash types and 7,000 vpd for fatal and injury crashes, were more accurate models than using a single grouping of AADT. Weather-related crashes were found to reduce the dispersion parameter and Akaike information criterion when comparing models including weather-related crashes and models excluding weather-related crashes. SPFs were developed for weather-related crashes: one with AADT ≤ 6,000 vpd and one with AADT > 6,000 vpd. Six SPFs were developed for undivided rural two-lane roadways, including all crash types and fatal and injury crashes.
Book Synopsis The Art of Regression Modeling in Road Safety by : Ezra Hauer
Download or read book The Art of Regression Modeling in Road Safety written by Ezra Hauer and published by Springer. This book was released on 2016-10-07 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book explains how to fashion useful regression models from commonly available data to erect models essential for evidence-based road safety management and research. Composed from techniques and best practices presented over many years of lectures and workshops, The Art of Regression Modeling in Road Safety illustrates that fruitful modeling cannot be done without substantive knowledge about the modeled phenomenon. Class-tested in courses and workshops across North America, the book is ideal for professionals, researchers, university professors, and graduate students with an interest in, or responsibilities related to, road safety. This book also: · Presents for the first time a powerful analytical tool for road safety researchers and practitioners · Includes problems and solutions in each chapter as well as data and spreadsheets for running models and PowerPoint presentation slides · Features pedagogy well-suited for graduate courses and workshops including problems, solutions, and PowerPoint presentations · Equips readers to perform all analyses on a spreadsheet without requiring mastery of complex and costly software · Emphasizes understanding without esoteric mathematics · Makes assumptions visible and explains their role and consequences
Download or read book Guide for Pavement Friction written by and published by AASHTO. This book was released on 2008 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report contains guidelines and recommendations for managing and designing for friction on highway pavements. The contents of this report will be of interest to highway materials, construction, pavement management, safety, design, and research engineers, as well as others concerned with the friction and related surface characteristics of highway pavements.
Book Synopsis Median Cross-section Design for Rural Divided Highways by : Jerry L. Graham (Verkehrsingenieur.)
Download or read book Median Cross-section Design for Rural Divided Highways written by Jerry L. Graham (Verkehrsingenieur.) and published by . This book was released on 2014 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: "TRB's National Cooperative Highway Research Program (NCHRP) Report 794: Median Cross-Section Design for Rural Divided Highways provides guidelines for designing typical cross-sections for medians on new and existing rural freeways and divided highways."--Publisher's description.
Book Synopsis Developing Safety Performance Functions for Two-way Stop-controlled Intersections in Louisiana by : Ming Sun
Download or read book Developing Safety Performance Functions for Two-way Stop-controlled Intersections in Louisiana written by Ming Sun and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Pedestrian Facilities Users Guide: Providing Safety and Mobility by : Charles V. Zegeer
Download or read book Pedestrian Facilities Users Guide: Providing Safety and Mobility written by Charles V. Zegeer and published by DIANE Publishing. This book was released on 2002 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: This guide is intended to provide information on how to identify safety and mobility needs for pedestrians with the roadway right-of-way. Useful for engineers, planners, safety professionals and decision-makers, the guide covers such topics as: the Walking Environment including sidewalks, curb ramps, crosswalks, roadway lighting and pedestrian over and under passes; Roadway Design including bicycle lanes, roadway narrowing, reducing the number of lanes, one-way/two-way streets, right-turn slip lanes and raised medians; Intersections with roundabouts, T-intersections and median barriers; and Traffic calming designs.
