Download or read book Calibration and Development of Safety Performance Functions for Rural Highway Facilities in Idaho written by Matthew C. Sipple and published by . This book was released on 2014 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the reduction of highway fatalities continues to be a point of emphasis for the U.S. Department of Transportation, many state and local agencies have incorporated safety enhancements into planning, design, operations, and maintenance. In 2010, the American Association of State Highway and Transportation Officials (AASHTO) released the Highway Safety Manual (HSM) as a resource to include safety in decision making for transportation professionals. AASHTO developed general safety performance functions (SPF) to predict crash frequencies based on crash data from various jurisdictions, and suggested that agencies calibrate those SPFs to local crash data and/or develop jurisdiction-specific safety performance functions. At the request of the Idaho Transportation Department (ITD), calibration factors were generated to calibrate the HSM SPFs for rural two-lane, two-way highways and rural stop controlled intersections based on Idaho crash history. In addition, new statewide SPFs were developed for the same rural facilities.
Download or read book Calibration of the Highway Safety Manual Safety Performance Function and Development of Jurisdiction specific Models for Rural Two lane Two way Roads in Utah written by Bradford Brimley and published by . This book was released on 2011 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study area was the state of Utah. Crash data from 2005-2007 on 157 selected study segments provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new SPFs. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16. This indicates that the HSM underpredicts the number of crashes on rural two-lane two-way roads in Utah by sixteen percent.
Download or read book Calibration of the Highway Safety Manual Safety Performance Function and Development of Jurisdiction specific Models for Rural Two lane Two way Roads in Utah written by Bradford Brimley and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study area was the state of Utah. Crash data from 2005-2007 on 157 selected study segments provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new SPFs. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16. This indicates that the HSM underpredicts the number of crashes on rural two-lane two-way roads in Utah by sixteen percent.
Download or read book Transportation Safety Data and Analysis written by Grant G. Schultz and published by . This book was released on 2011 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report documents the calibration of the Highway Safety Manual (HSM) safety performance function (SPF) for rural two-lane two-way roadway segments in Utah and the development of new models using negative binomial and hierarchical Bayesian modeling techniques. Crash data from 2005-2007 on 157 selected study segments in Utah provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new models. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16, indicating that the HSM underpredicts the number of crashes on these roads by 16 percent. Negative binomial regression was used to develop four new models, and one additional model was developed using hierarchical (or full) Bayesian techniques. The empirical Bayes (EB) method can be applied with each negative binomial model because the models include an overdispersion parameter used with the EB method. The hierarchical Bayesian technique accounts for high levels of uncertainty. Because the hierarchical Bayesian model produces a density function of a predicted crash frequency, a comparison of this density function with an observed crash frequency can help identify segments with significant safety concerns. Each model has its own strengths and weaknesses, which include its data requirements and predicting capability. This report recommends that UDOT use the negative binomial model with transformed average annual daily traffic (AADT) at a 95 percent confidence level (Equation 5-11) for predicting crashes. This model produces accurate results and requires less data than other models. The hierarchical Bayesian process should be used for identifying segments with extreme crash frequencies that may benefit from safety improvements.
Download or read book Regional Considerations of the Rocky Mountains and Plains Regions in Calibrating Safety Performance Function on Rural Two lane Highwasy and Interstate Freeways written by Rameshwor Chalise and published by . This book was released on 2016 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: The American Association of State Highway and Transportation Officials, AASHTO’s Highway Safety Manual (HSM) was first released in 2010 and is considered as a significant milestone in the advancement of the practice of road safety analysis. An extensive workforce spearheaded by the Transportation Research Board (TRB) Committee gave a result in the form of the first Highway Safety Manual in the United States. The HSM has already been proven as a great asset in traffic safety practice and also in research related to traffic safety since it bridges the gap between the state-of-the-art of research and practice. The HSM’s analytical tools and techniques help to quantify the traffic safety and help in evaluation as well as decision making in planning design, operation, and maintenance. There are a number of states and transportation authorities which are already using the HSM along with the AASHTO design guide. Although the HSM is the sole national source for quantitative evaluation of traffic safety, it has some limitations and there remains some room for improvement. Safety Performance Functions are statistical models to predict the expected number of crashes per year for a certain roadway facility as a function of traffic, and, in some cases, roadway characteristics, and weather conditions. Simple SPFs are mostly developed using Average Annual Daily Traffic (AADT) only while Full SPFs consider additional factors to traffic such as roadway geometry, driver characteristics, and weather conditions. Part C-Predictive Methods in the HSM includes the calibration procedure of SPFs as well as guidelines on how to calibrate jurisdiction-specific SPFs. The main limitation in the HSM Part C is that the Safety Performance Functions (SPFs) for different road facilities were developed using data from only few states in the United States. Thus the provided SPFs cannot adequately represent all states and regions since each of the states has a different geographical features, weather conditions, crash reporting thresholds, and demographic attributes. The main goal of this research is to apply and validate some of the HSM parts; Part C, to Wyoming specific conditions. In this thesis, Wyoming-specific SPFs were developed using crash data and traffic data from 2003 to 2013 for both total crashes and fatal and injury (F+I) crashes. All the rural two-lane two-way roadways and interstate freeways were considered in developing Wyoming-specific Simple SPFs, however, segments were chosen randomly from different parts of the state to develop Wyoming-specific Full SPFs. Negative Binomial (NB) model was used to develop SPFs for both interstate freeways and two-lane two-way roadways. Also, Zero-Inflated Poisson (ZIP) model was developed for two-lane two-way roadways and compared with the NB model. Statistical goodness-of-fit tests were performed on the calibrated models. The results were compared in order to assess the transferability of the HSM SPFs in Wyoming. It was found that the HSM SPFs cannot be applied directly in the state of Wyoming. While Simple SPFs under-estimated and over-estimated the number of crashes for different roadway segments and severity levels, Wyoming-specific Full SPFs provided more accurate and precise crash prediction.
Download or read book Calibration and Development of State DOT specific Safety Performance Functions written by Vikash Varun Gayah and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Calibration of Wyoming specific Safety Performance Functions for Urban and Suburban Five lane Arterial Roadway Corridors written by Ahmad E. Belhamad Elterkawi and published by . This book was released on 2017 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: Urban and suburban arterials play a major role in the roadway network system. They provide accessibility and mobility to major zones of cities. According to the National Highway Transportation Safety Administration (NHTSA), 14,414 fatal crashes occurred on urban roadways during 2015 which constitutes about 45 percent of the total 32,166 traffic fatalities in the US. In Wyoming, urban roads experienced 1,630 fatal and injury crashes in 2015 that accounted for about 56 percent of total fatalities and injuries (2,924 fatal and injury crashes). The role of urban arterials in accessibility and mobility as well as the number of fatalities highlights the importance of evaluating their traffic safety. Predictive methods are needed to evaluate traffic safety of urban arterials. The main objective of this study is to understand contributing factors to crashes on five-lane arterials with a center two-way left-turn lane (TWLTL) (5T) and urban and suburban arterial signalized four-leg intersections (4SG). This better understanding will help the Wyoming Department of Transportation (WYDOT) to identify appropriate safety countermeasures to reduce the frequency and severity of crashes. The study assessed also the transferability of the Highway Safety Manual (HSM) to Wyoming conditions. Moreover, the calibrated HSM Safety Performance Functions were compared to a newly developed Wyoming-specific SPFs. The objectives of this study are accomplished by undertaking a number of tasks. The HSM SPFs are calibrated for urban and suburban 5T segment and 4SG intersections. The Wyoming-specific SPFs were also developed for the same two facilities. The study compared the calibrated HSM SPFs and the developed Wyoming-specific models. Since these two roadway facilities are spatially and temporally correlated, the two facilities could be analyzed as one entity (i.e., urban/ suburban corridors). Another set of SPFs were developed for urban and suburban 5T/4SG corridors. The performance of the corridor models were also cross-validated against the performance of segment and intersection SPFs. All SPFs were developed using Negative Binomial (NB) distribution for three levels of severity. It was found that the HSM SPFs over-estimated the total crashes for 5T segments and 4SG intersections in Wyoming. The Wyoming-specific SPFs performed better than the calibrated HSM SPFs in predicting total crashes in those two facilities. However, the Wyoming-specific 5T/4SG corridor models performed better than their individual segment and intersection counterparts. In general, Wyoming-specific models for the three facilities slightly over-estimated the fatal and injury crashes. The findings of this study may help the Wyoming Department of Transportation to better evaluate the safety of urban arterial roadways, intersections, and corridors in Wyoming.
Download or read book Calibration of Highway Safety Manual Safety Performance Functions for Freeway Ramp Terminals in Virginia written by Justice Appiah and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 19 of the Highway Safety Manual (HSM) provides safety performance functions (SPFs) for freeway ramps and crossroad terminals. The chapter includes 56 predictive models for ramp terminals characterized by terminal type, intersection control, crash severity, area type, and number of crossroad lanes. These SPFs were developed with data from other states and need to be calibrated to Virginia conditions to ensure that they accurately reflect the driver population and environment. The application of uncalibrated SPFs may produce misleading results, compromise safety outcomes, and lead to inappropriate design decisions. This study conducted systematic calibration of the HSM ramp terminal SPFs to account for conditions in Virginia. This involved determining appropriate multipliers or functions that aligned the expected average crash frequencies estimated using HSM methodologies with field-observed crash frequencies from selected sites. A review of cumulative residual plots for fitted values suggested that using a single calibration factor as a multiplier to adjust the HSM ramp terminal SPF predictions did not provide a good fit to Virginia data. Consequently, calibration functions were developed that provided a better fit of Virginia data to the HSM ramp terminal SPF predictions. Limiting the number of crash modification factors to 3 instead of using all 11 applicable crash modification factors resulted in a marginally better fit of the data.
Download or read book Estimating Calibration Factors and Developing Calibration Functions for the Prediction of Crashes at Urban Intersections in Kansas written by Rijesh Karmacharya and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Kansas experienced about 60,000 crashes annually from 2013 to 2016, 25% of which occurred at urban intersections. Hence, urban intersections in Kansas are one of the most critical locations in terms of frequency of crashes. Therefore, an accurate prediction of crashes at these locations would help identify critical intersections with a higher probability of an occurrence of crash, which would help in selecting appropriate countermeasures to reduce those crashes. The crash prediction models provided in the Highway Safety Manual (HSM) predict crashes using traffic and geometric data for various roadway facilities, which are incorporated through Safety Performance Functions (SPFs) and Crash Modification Factors. The primary objective of this study was to estimate calibration factors for different types of urban intersection in Kansas. This study followed the crash prediction method and calibration procedure provided in the HSM to estimate calibration factors for four different urban intersection types in Kansas: 3-leg unsignalized intersections with stop control on the minor approach (3ST), 3-leg signalized intersections (3SG), 4-leg unsignalized intersections with stop control on the minor approach (4ST), and 4-leg signalized intersections (4SG). Following the HSM methodology, the required data elements were collected from various sources. The Annual Average Daily Traffic (AADT) data were extracted from Kansas Crash Analysis & Reporting System (KCARS) database and GIS Shapefiles downloaded from Federal Highway Administration website. For some of 3ST and 3SG intersections, minor-street AADT was not available. Hence, multiple linear regression models were developed for the estimation of minor-street AADT. Crash data were extracted from the Kansas Crash Analysis and Reporting System database, and other geometric data were extracted using Google Earth. The HSM requirement for sample size is 30 to 50 sites, with at least 100 crashes per year for the study period for the combined set of sites. In this study, the study period for 3ST, 3SG, and 4SG intersections were taken as 2013 to 2015, and 2014 to 2016 for 4ST, based on the availability of recent crash data at the beginning of the calibration procedure for each facility type. The sample size considered for calibration was 234 for 3ST, 89 for 3SG, 167 for 4ST, and 198 for 4SG intersections. Out of the 234 3ST intersections, minor-street AADT was estimated using multiple linear regression models for 106 intersections. For 3SG intersections, minor-street AADT was estimated for 21 out of the 89 intersections. The calibration factors for these facility types were estimated to be 0.64 for 3SG, 0.51 for 3ST, 1.17 for 4SG, and 0.61 for 4ST when considering crashes of all severities. Considering only the fatal and injury crashes, the calibration factors were estimated as 0.52 for 3SG, 0.40 for 3ST, 2.00 for 4SG, and 0.73 for 4ST. The calibration factors show that the HSM methodology underpredicted crashes for 4SG, and overpredicted crashes for other three intersection types. The reliability of the calibration factors was assessed with the help of Cumulative Residual plots and coefficient of variation. The results from the goodness-of-fit tests showed that the calibration factors were not reliable and showed bias in the prediction of crashes. Hence, calibration functions were developed, and their reliability were examined. The results showed that calibration functions had better reliability as compared to calibration factors, with more accuracy in crash prediction. The findings from this study can be used to identify intersections with a higher probability of having crashes in the future. Suitable countermeasures can be applied at critical locations which would help reduce the number of crashes at urban intersections in Kansas; thus increasing the safety.
Download or read book Calibration of Highway Safety Manual Prediction Models for Freeway Segments Speed change Lanes Ramp Segments and Crossroad Ramp Terminals in Kansas written by Imalka Chiranthi Matarage and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Crash prediction models in the Highway Safety Manual (HSM) are used to quantify the safety experience of existing and new roadways. Safety performance functions (SPFs) or crash prediction models are statistical formulas developed on limited data from a few selected states, Kansas not being one of those states. Therefore, the HSM recommends calibration of HSM-default SPFs, or development of local SPFs, to enhance accuracy of predicted crash frequency. This dissertation demonstrates the HSM calibration procedure and its' quality assessment for freeway segments, speed-change lanes, ramp segments, and crossroad ramp terminals in Kansas. The study used three years of recent crash data, the most recent geometric data, and HSM-recommended sample sizes for all facilities considered for the calibration. The HSM methodology overpredicted all fatal and injury (FI) crashes and underpredicted all property damage only (PDO) crashes for freeway segments. The HSM methodology consistently underpredicted both FI and PDO crashes for both entrance- and exit-related speed-change lanes. The HSM methodology overpredicted all FI crashes, underpredicted multiple vehicle PDO crashes, and overpredicted single vehicle PDO crashes for entrance ramp segments. In the case of exit ramp segments, the HSM methodology underpredicted all multiple vehicle crashes and overpredicted all single vehicle crashes. The HSM methodology overpredicted all FI crashes and underpredicted all PDO crashes for both signal- and stop-controlled crossroad ramp terminals. Cumulative residual plots and coefficient of variation were used to evaluate the quality of calibrated HSM-default SPFs. Results of calibration quality assessment indicated that estimated calibration factors were satisfactory for all freeway and ramp facilities considered in this study. However, for further accuracy and comparison purposes, calibration functions were developed to improve the fit to local data. Calibration functions were better fitted compared to calibrated HSM-default SPFs for freeway and ramp facilities in Kansas. Challenges faced, how those challenges were addressed, and data collection techniques used in this study are discussed. In summary, estimated calibration factors and developed calibration functions of this study would greatly improve making accurate decisions related to freeway and ramp safety in Kansas.
Download or read book Calibrating the Highway Safety Manual Predictive Methods for Oregon Rural State Highways written by Fei Xie and published by . This book was released on 2011 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first edition of the Highway Safety Manual (HSM) provides a quantitative approach to predict the safety of transportation facilities based on the recently developed scientific methods. This approach, known as the predictive method, was developed for several states in the United States. Due to differences in driver population, weather condition and other issues, the State of Oregon is expected to calibrate these predictive models before using them. By locality, the existing predictive methods can be divided into two parts: rural highway predictive method and urban highway predictive method. This thesis focuses on the calibration project for the rural predictive models. Therefore, in the first part of this thesis, the author will illustrate the calibration process and calibration results for the rural facility types, including rural two-lane, two-way roads and rural multilane highways. Also, after the calibration project, the author found a new calibration sample size estimation procedure which is more statistically reliable than the current HSM sample size determination process. This new statistical estimation method will be explained and recommended for future calibration projects.
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.
Download or read book Traffic Monitoring Guide written by United States. Federal Highway Administration. Office of Highway Information Management and published by . This book was released on 1992 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transportation Decision Making written by Kumares C. Sinha and published by John Wiley & Sons. This book was released on 2011-09-09 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: This pioneering text provides a holistic approach to decisionmaking in transportation project development and programming, whichcan help transportation professionals to optimize their investmentchoices. The authors present a proven set of methodologies forevaluating transportation projects that ensures that all costs andimpacts are taken into consideration. The text's logical organization gets readers started with asolid foundation in basic principles and then progressively buildson that foundation. Topics covered include: Developing performance measures for evaluation, estimatingtravel demand, and costing transportation projects Performing an economic efficiency evaluation that accounts forsuch factors as travel time, safety, and vehicle operatingcosts Evaluating a project's impact on economic development and landuse as well as its impact on society and culture Assessing a project's environmental impact, including airquality, noise, ecology, water resources, and aesthetics Evaluating alternative projects on the basis of multipleperformance criteria Programming transportation investments so that resources can beoptimally allocated to meet facility-specific and system-widegoals Each chapter begins with basic definitions and concepts followedby a methodology for impact assessment. Relevant legislation isdiscussed and available software for performing evaluations ispresented. At the end of each chapter, readers are providedresources for detailed investigation of particular topics. Theseinclude Internet sites and publications of international anddomestic agencies and research institutions. The authors alsoprovide a companion Web site that offers updates, data foranalysis, and case histories of project evaluation and decisionmaking. Given that billions of dollars are spent each year ontransportation systems in the United States alone, and that thereis a need for thorough and rational evaluation and decision makingfor cost-effective system preservation and improvement, this textshould be on the desks of all transportation planners, engineers,and educators. With exercises in every chapter, this text is anideal coursebook for the subject of transportation systems analysisand evaluation.
Download or read book Guidelines and Recommendations to Accommodate Older Drivers and Pedestrians written by L. K. Staplin and published by . This book was released on 2001 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Redundancy in Highway Bridge Superstructures written by Michel Ghosn and published by Transportation Research Board. This book was released on 1998 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Strategies for Work Zone Transportation Management Plans written by Leverson Boodlal and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the ways a state department of transportation or other transportation agency can address work zone safety and other impacts is to develop and implement a Transportation Management Plan (TMP). The TRB National Cooperative Highway Research Program's NCHRP Research Report 945: Strategies for Work Zone Transportation Management Plans provides a practitioner-ready guidebook on how to select and implement strategies that improve safety and traffic operations in roadway construction work zones. Supplemental materials to the report include NCHRP Web-Only Document 276: Evaluating Strategies for Work ZoneTransportation Management Plans; fact sheets on ramp meter, reversible lane, and truck restrictions; and guidebook appendices.
