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Assessment Of Statewide Intersection Safety Performance
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Book Synopsis Research Project Work Plan for Assessment of Statewide Intersection Safety Performance by : Christopher Michael Monsere
Download or read book Research Project Work Plan for Assessment of Statewide Intersection Safety Performance written by Christopher Michael Monsere and published by . This book was released on 2008 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Assessment of Statewide Intersection Safety Performance by :
Download or read book Assessment of Statewide Intersection Safety Performance written by and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Assessment of Statewide Intersection Safety Performance by : Christopher Michael Monsere
Download or read book Assessment of Statewide Intersection Safety Performance written by Christopher Michael Monsere and published by . This book was released on 2011 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Statewide Highway Safety Program Assessment by : United States. National Highway Traffic Safety Administration
Download or read book Statewide Highway Safety Program Assessment written by United States. National Highway Traffic Safety Administration and published by . This book was released on 1975 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. National Highway Traffic Safety Administration. Planning and Evaluation Publisher : ISBN 13 : Total Pages :147 pages Book Rating :4.:/5 (184 download)
Book Synopsis Statewide Highway Safety Program Assessment by : United States. National Highway Traffic Safety Administration. Planning and Evaluation
Download or read book Statewide Highway Safety Program Assessment written by United States. National Highway Traffic Safety Administration. Planning and Evaluation and published by . This book was released on 1975 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Michigan Urban Trunkline Intersections Safety Performance Functions (SPFs) Development and Support by :
Download or read book Michigan Urban Trunkline Intersections Safety Performance Functions (SPFs) Development and Support written by and published by . This book was released on 2015 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study involves the development of safety performance functions (SPFs) for signalized and stop-controlled intersections located along urban and suburban arterials in the state of Michigan. Extensive databases were developed that resulted in the integration of traffic crash information, traffic volumes, and roadway geometry information. After these data were assembled, an exploratory analysis of the data was conducted to identify general crash trends. This included assessment of the base models provided in the Highway Safety Manual (HSM), as well as a calibration exercise, which demonstrated significant variability in terms of the goodness-of-fit of the HSM models across various site types. Michigan-specific SPFs were estimated, including simple models that consider only annual average daily traffic (AADT). More detailed models were also developed, which considered additional geometric factors, such as posted speed limits, number of lanes, and the presence of medians, intersection lighting, and right-turn-on-red prohibition. Crash modification factors (CMFs) were also estimated, which can be used to adjust the SPFs to account for differences related to these factors. Separate SPFs were estimated for intersections of only two-way streets and for those where at least one of the intersecting streets was one-way as the factors affecting traffic safety were found to vary between these site types. Severity distribution functions (SDFs) were also estimated, which can be used to predict the proportion of injury crashes which result in different injury severity levels. The SDFs may include various geometric, operation, and traffic variables that will allow the estimated proportion to be specific to an individual intersection. Ultimately, the results of this study provide MDOT with a number of methodological tools that will allow for proactive safety planning activities, including network screening and identification of high-risk sites. These tools have been calibrated such that they can be applied at either the statewide level or within any of MDOT's seven geographic regions, providing additional flexibility to accommodate unique differences across the state. The report also documents procedures for maintaining and calibrating these SPFs over time, allowing for consideration of general trends that are not directly reflected by the predictor variables.
Book Synopsis Developing Safety Performance Functions for Wyoming Urban and Suburban Four-leg Signalized Intersections by : Sadia Sharmin
Download or read book Developing Safety Performance Functions for Wyoming Urban and Suburban Four-leg Signalized Intersections written by Sadia Sharmin and published by . This book was released on 2018 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The complexity of traffic movements at signalized intersections is of a significant interest to transportation professionals due to a disproportional high amount of conflicts and crashes involving turning vehicles followed by through vehicles. Moreover, the wide variability in geometric and operational characteristics at signalized intersections may exacerbate this complexity. Intersection-related fatalities in Wyoming exhibited a sharp increase after 2012. Fatality rate in Wyoming exceeded the national rate by 12 percent in 2014 and 2015. In 2015, Wyoming’s urban intersections crashes constituted 50% of total urban crashes while that the proportion at the national level in the US was 32%. These issues could be addressed through successful engineering approaches which necessitate reliable methods to estimate intersection safety. Currently, Safety Performance Functions (SPFs) are used as the main tool to estimate traffic safety of different roadway elements including intersections. The Highway Safety Manual (HSM), published by the American Association of State Highway and Transportation Officials (AASHTO) in 2010 provides SPFs for intersections. The unique nature and distinct attributes of Wyoming also necessitates developing its own jurisdiction-specific SPFs. SPFs are needed to identify potential candidate locations for safety improvements and for implementation of various safety countermeasures. Therefore, the research in this thesis focuses on calibrating SPFs for four-leg signalized intersections in Wyoming. The thesis also utilizes advanced statistical techniques to address various issues in crash data at intersections. Crash data at four-leg signalized intersections were structured as pooled data averaged across time and panel data with respect to time. The key issues addressed in this study include: i) addressing overdispersion characteristics of crash data, ii) considering unobserved random effects of the intersections due to their heterogeneity, and iii) allowing the effects of the confounding factors on intersection crash trends over time. This study examined the effects of geometry, weather, traffic and driver characteristics on crash frequencies incorporating time trends and taking longer time frames into consideration. Standard crash models using longer time frames and aggregated data do not consider time-varying effects on crash frequency, and can introduce error due to unobserved heterogeneity. This study analyzed the findings among traditional Negative Binomial (NB) model (using pooled and panel data) which account for the overdispersion of data, Random Effect Negative Binomial (RENB) model using panel data that consider unobserved random effects of the sites due to their heterogeneity and Generalized Estimating Equation (GEE) with Negative Binomial (NB) distribution. RENB model outperformed NB models by comparing the Akaike Information Criterion (AIC) values and hence, RENB models were chosen to explain the effects of the confounding factors on the crash counts. A marginal model approach which is different from the random effect approach was attempted through applying GEE to the panel data. “Time” was included as an explanatory variable with linear and quadratic effects to investigate the crash trends across time. The interactions of variables with “time” were considered to determine the effect of fixed variables over time. GEE was also fitted using variables without incorporating “time”, however, GEE accounting for “time” performed better. Model assessment was performed using the quasi-likelihood information criterion (QIC). This method also showed that the GEE model with autoregression structure had the best model performance. Installing left-turn lanes at signalized intersections physically separates left-turning vehicles, hence can reduce the number of conflicts by removing slow or decelerating vehicles from through traffic resulting in safer operations. The safety effectiveness of left-turn lanes at four-leg signalized intersections was estimated with these approaches along with predicting and describing the confounding factors. The aforementioned objectives were attained by developing SPFs using 174 four-leg signalized intersections crash data of Wyoming from the years 2005 through 2014. Wyoming specific data, including traffic, weather and driver characteristics, were incorporated into the models along with site-specific geometric characteristics. The results of this study highlighted the advantages of predicting crash frequencies by crash type and severity. To examine the impact of weather on intersections crashes, three sets of SPFs were calibrated; winter, summer, and all year. The cross-sectional panel data analysis for evaluating the safety effectiveness of adding left-turn lanes at four-leg signalized intersections indicated a reduction of Fatal+Injury (F+I) and angle crashes by 21.6% and 30.8%, respectively. The calibrated models for the winter indicated a reduction of 19.4% and 38.8% for the aforementioned crashes, respectively for adding left-turn lanes. For the summer, crash reduction for these crashes for the same treatment were found 71% and 69%, respectively.
Book Synopsis Development of a Design Based Intersection Safety Performance Evaluation Tool by : Adam J. Kirk
Download or read book Development of a Design Based Intersection Safety Performance Evaluation Tool written by Adam J. Kirk and published by . This book was released on 2013 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Safety Evaluation of Continuous Green T Intersections by : Eric T. Donnell
Download or read book Safety Evaluation of Continuous Green T Intersections written by Eric T. Donnell and published by . This book was released on 2016 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Safety Performance Evaluation of Intersection Traffic and Safety Assets by : Han Gyol Kim
Download or read book Safety Performance Evaluation of Intersection Traffic and Safety Assets written by Han Gyol Kim and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Rural Expressway Intersection Characteristics that Contribute to a Reduced Safety Performance by : Garrett David Burchett
Download or read book Rural Expressway Intersection Characteristics that Contribute to a Reduced Safety Performance written by Garrett David Burchett and published by . This book was released on 2005 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expressways have been constructed in many states as a way to increase mobility without the expense of a full access-controlled or grade-separated facility. In most cases, it was assumed that these segments of highway would produce similar mobility and safety characteristics as other access-controlled facilities. However, recent research has found that there are problems with the safety performance of these systems. Although past research has been completed to examine the nature of crashes on these facilities, it is the purpose of this study to continue the research and analyze the common characteristics of the intersections. The intersections studied in this research were located throughout the state of Iowa. The objective of these analyses is to provide an identification of the major contributing factors that create problematic intersections in the state of Iowa. From previous research, it is evident that factors in addition to roadway volume contribute to the safety performance of an at-grade, two-way, stop-controlled expressway intersection. This research identifies common characteristics that may increase or decrease the safety performance of a rural expressway intersection. The methodology used in this research includes the examination of 644 intersections throughout the state of Iowa. Through the use of a statewide database and crash information from 1996 to 2000, we were able to identify the 100 best- and 100 worst-performing intersections based on crash severity rate. With the 200 intersections, a statistical analysis was completed to determine the effects intersection design and surrounding land use have on the intersection's safety performance. The safety performance of intersections located on vertical/horizontal curves, skewed intersections, and varying surrounding land use were studied to determine their effects on rural expressway intersections. Following the completion of the analysis of the 200 intersections, 30 intersections with highest crash severity index rates were selected for more thorough, site-specific analysis. As part of this analysis, we examined the impact of land use adjacent to the intersection and the impact of peaking in hourly traffic volumes. The research identifies attributes that impact crash severity both negatively and positively. Through the identification of these attributes, designers and planners can more adequately address safety concerns on rural expressway intersections.
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 Evaluation of Signalized Intersection Safety Using Centracs System by : Xinkai Wu
Download or read book Evaluation of Signalized Intersection Safety Using Centracs System written by Xinkai Wu and published by . This book was released on 2017 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Safety Effectiveness of High-speed Expressway Signals by : Reginald R. Souleyrette
Download or read book Safety Effectiveness of High-speed Expressway Signals written by Reginald R. Souleyrette and published by . This book was released on 2005 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The safety benefit of signalizing intersections of high-speed divided expressways is considered. Analyses were conducted on 50 and 55 mph and on 55 mph only intersections, comparing unsignalized and signalized intersections. Results of the 55 mph analysis are included in this report. Matched-pair analysis indicates that generally, signalized intersections have higher crash rate but lower costs per crash. On the other hand, before-and-after analysis (intersections signalized between 1994 and 2001) indicates lower crash rates (~30 percent) and total costs (~10 percent) after signalization. Empirical Bayes (EB) adjusted before-and-after analysis reduces estimates of safety benefit (crash rate) to about 20 percent. The study shows how commonly used analyses can differ in their results, and that there is great variability in the safety performance of individual signalized locations. This variability and the effect of EB adjustment are demonstrated through the use of innovative graphics.
Book Synopsis Regression Analysis of Count Data by : Adrian Colin Cameron
Download or read book Regression Analysis of Count Data written by Adrian Colin Cameron and published by Cambridge University Press. This book was released on 2013-05-27 with total page 597 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides the most comprehensive and up-to-date account of regression methods to explain the frequency of events.
Book Synopsis Developing Safety Performance Functions for 4-leg Single-lane Roundabouts Based on Oregon Data by : Jianfei Zheng
Download or read book Developing Safety Performance Functions for 4-leg Single-lane Roundabouts Based on Oregon Data written by Jianfei Zheng and published by . This book was released on 2013 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: Roundabouts have become an alternative for traditional intersections due to the safer operational performance. Previous research has provided crash modification factors (CMFs) as a criterion based on before-after studies as to evaluate the safety performance of roundabouts. One drawback of assessment based on crash modification factors, however, is that a before-after study includes too many variations at a time that it only provides a general idea of the safety performance for roundabouts. Since the industrial world is interested in the safety outcome of converting traditional intersections to roundabouts, safety performance functions (SPFs) will provide more specific details on estimating crashes than that of crash modification factors. This thesis will adopt a similar methodology that has been used in the current Highway Safety Manual (HSM) to develop safety performance functions for roundabouts based on Oregon data. The outcome of this thesis will help the Oregon Department of Transportation (ODOT) to evaluate existing roundabouts in the State of Oregon. Furthermore, this thesis will function as an additional case study from Oregon to contribute to the national effort of evaluating the safety performance of roundabouts.
