Development of Safety Performance Functions for Two-lane Roads Maintained by the Virginia Department of Transportation - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Development of Safety Performance Functions for Two-lane Roads Maintained by the Virginia Department of Transportation write by Nicholas J. Garber. This book was released on 2010. Development of Safety Performance Functions for Two-lane Roads Maintained by the Virginia Department of Transportation available in PDF, EPUB and Kindle. 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.
Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia
Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia write by Hyun W. Cho. This book was released on 2020. Development of a Systemic Safety Improvement Plan for Two-Lane Rural Roads in Virginia available in PDF, EPUB and Kindle. 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.
Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation
Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation write by Nicholas J. Garber. This book was released on 2010. Safety Performance Functions for Intersections on Highways Maintained by the Virginia Department of Transportation available in PDF, EPUB and Kindle. 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.
Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation
Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation write by Young-Jun Kweon. This book was released on 2014. Development of Safety Performance Functions for Multilane Highway and Freeway Segments Maintained by the Virginia Department of Transportation available in PDF, EPUB and Kindle. 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.
Development of Safety Performance Functions for Two-lane Roads in Virginia
Development of Safety Performance Functions for Two-lane Roads in Virginia - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Development of Safety Performance Functions for Two-lane Roads in Virginia write by Phillip R. Haas. This book was released on 2009. Development of Safety Performance Functions for Two-lane Roads in Virginia available in PDF, EPUB and Kindle.
