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Development Of Safety Performance Functions For Restricted Crossing U Turn Rcut Intersections
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Book Synopsis Development of Safety Performance Functions for Restricted Crossing U-turn (RCUT) Intersections by :
Download or read book Development of Safety Performance Functions for Restricted Crossing U-turn (RCUT) Intersections written by and published by . This book was released on 2019 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Florida State University researchers developed guidance to assist planners in deciding where to place restricted crossing U-turns (RCUTs).
Book Synopsis Safety Evaluation of Signalized Restricted Crossing U-turn Intersections by : Joseph E. Hummer
Download or read book Safety Evaluation of Signalized Restricted Crossing U-turn Intersections written by Joseph E. Hummer and published by . This book was released on 2017 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: Technical summary of the FHA report FHWA-HRT-17-082 program that studied evaluated restricted crossing U-turn (RCUT) intersection and was conducted by the DCMF program for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study.
Book Synopsis Safety Evaluation of Restricted Crossing U-turn Intersection by :
Download or read book Safety Evaluation of Restricted Crossing U-turn Intersection written by and published by . This book was released on 2017 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document is a technical summary of the Federal Highway Administration report Development of a Crash Modification Factor for Signalized RCUTs (FHWA-HRT-17-082). This research examined the safety impacts of replacing a traditional signalized intersection with a signalized restricted crossing U-turn intersection (RCUT). An RCUT is defined as a three-approach or four-approach intersection where minor street left-turn and through movements (if any) are rerouted to one-way downstream U-turn crossovers. The objective was to estimate the safety effectiveness of this strategy as measured by crash frequency. The primary measures examined were based on total crashes and fatal and injury crashes. A further objective was to conduct a spatial patterns analysis, assessing notable clusters of crashes, as well as changes to crash types and day/night between the before and after periods.
Book Synopsis Safety Performance of Median U-turn Intersections by : Jonathan James Kay
Download or read book Safety Performance of Median U-turn Intersections written by Jonathan James Kay and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of alternative intersection designs can provide both safety and operational benefits for road users at potentially lower costs when implemented in the appropriate setting. The Federal Highway Administration has previously recognized a subset of alternative intersections designs broadly referred to as "reduced left-turn conflict intersections" as a proven safety countermeasure that have been shown to decrease the risk of potentially severe crash types by reducing conflict points through the use of indirect left-turn movements. Median U-turn intersections (also referred to as "Michigan lefts" or "boulevard turnarounds") are one such alterative design that accommodates indirect left-turn movements via directional U-turn crossovers located within the median along one or both of the intersecting roadways. Michigan has long been a pioneer in the implementation of median U-turns along urban and suburban divided boulevards, with initial installations dating back several decades. Additionally, various indirect left-turn configurations have been implemented along rural highways and frontage roads for urban freeways.While prior work has consistently demonstrated that median U-turn intersection designs represent an effective countermeasure that can improve operational performance and reduce the frequency of severe crash types when implemented in the appropriate context, much of the extant research is outdated and several important areas of investigation remain unexplored. This includes defining the appropriate crash influence area, the impacts of pre-conversion characteristics, impacts to pedestrian and bicycle collisions, and evaluating crashes pre/post conversion (e.g., longitudinal panel data) compared to a purely cross-sectional evaluation. To address these and other knowledge gaps, research was performed to quantify the safety performance characteristics and develop analytical tools related to the utilization of median U-turn intersections. Historical traffic crash data were collected for signalized and unsignalized intersections in Michigan where left-turns are accommodated by a median U-turn design. To allow for comparison of the performance between the median U-turn and traditional designs, data were also collected for a sample of reference intersections (divided and undivided) where conventional direct left-turn movements were maintained. A novel approach was developed to define the safety performance influence area of a median U-turn intersection, which subsequently improved the method of identifying and collecting target crash data. Utilizing the traffic crash data, a series of analyses were performed to identify the differences between conventional and median U-turn intersections, and to also identify the differences in safety performance between various median U-turn design characteristics. The analyses compared crash rates, types, severity distributions, and severe injury collision patterns, and included development of series of safety performance functions and crash modification factors. The results were then generalized into a series of recommendations for roadway agencies considering future implementation of median U-turn intersections, including specific design recommendations intended to improve safety performance for all road users.Ultimately, it was concluded that median U-turn designs represent an effective safety countermeasure to target the reduction of severe crash types for both unsignalized and signalized intersections. While there are some potential tradeoffs with respect to non-injury crash frequencies for specific pre-conversion configurations, the use of these indirect left-turn intersection designs is consistent with the Safe System approach adopted by the United States Department of Transportation within the National Roadway Safety Strategy. Unsignalized median U-turn intersections offer superior fatal and injury crash performance compared to conventional unsignalized intersections. The removal of the crossing conflict points at unsignalized median U-turn designs (which include a closed median at the intersection) essentially eliminates the pattern of severe head on left-turn and angle collisions occurring within conventional intersections. However, it is important to recognize that non-injury crashes were shown to increase when converting a conventional unsignalized intersection to a median U-turn at locations with an existing median on the major roadway.Signalized median U-turn intersections offer superior safety performance for both injury and non-injury crashes compared to conventional signalized intersections along undivided roadways. However, the comparison of median U-turns locations to conventional divided signalized intersections was limited by a lack of reference sites with comparable traffic volumes. Annual average frequencies of severe pedestrian and bicycle crashes were similar between the signalized median U-turn and conventional undivided sites. Finally, several design features of signalized median U-turn intersections were identified as having a significant impact on safety performance, including the distance to crossovers from the main intersection, the length of weaving areas, the number of signalized crossovers, and the number of storage lanes.
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 Field Evaluation of a Restricted Crossing U-turn Intersection by : Vaughan W. Inman
Download or read book Field Evaluation of a Restricted Crossing U-turn Intersection written by Vaughan W. Inman and published by . This book was released on 2012 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four-lane divided highways are an economical design solution to increase the capacity of rural highways compared to grade-separated limited access facilities. Compared to two-lane undivided rural highways, four-lane divided highways have markedly lower rates of sideswipe, rear-end, and head-on collisions. However, right-angle crash rates are markedly higher on four-lane divided highway intersections than at two-lane undivided highway intersections, largely as a result of left-turn and through movements from minor roads conflicting with far-side vehicles on the divided highway. The restricted crossing U-turn (RCUT) intersection is a promising treatment to mitigate right-angle crashes where two-lane minor roads intersect with rural four-lane divided highways. This report includes a comparison of operations at an RCUT intersection in Maryland with a roughly comparable conventional stop-controlled intersection on the same corridor. It also includes before-after crash analyses for intersections converted from conventional to RCUT designs on two Maryland highway corridors. The operational analysis found that conflicts between vehicles entering or crossing the highway from a minor road were reduced, weaving movements were about the same for the two intersection types, the RCUT design added about 1 min to travel time for vehicles making left-turn or through movements from the minor road. Three approaches were used to estimate the affect of an RCUT conversion on crashes. All three approaches led to the same conclusion: the RCUT design reduces crashes. A simple 3-year before and 3-year after analysis suggested a 30 percent decrease in the average number of crashes per year. An analysis that adjusted the observed crash rate at RCUT locations for the observed crash rate at nearby conventional intersections on the same corridors suggested a 28 percent decrease in the average annual number of crashes. An empirical Bayes analysis that adjusts for, among other things, the expected number of crashes at similar intersections and average annual traffic suggested a 44 percent decrease in crashes. Furthermore, the analyses suggest an overall reduction in crash severity with the RCUT design.
Book Synopsis Restricted Crossing U-turns at Rural Intersections by : Timothy Adams
Download or read book Restricted Crossing U-turns at Rural Intersections written by Timothy Adams and published by . This book was released on 2019 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study examines the potential for replacing the standard intersection design at two-way stop control (TWSC) and all-way stop control (AWSC) intersections along rural highways with a roundabout or a restricted crossing u-turn (RCUT) facility. The geometry of the RCUT design prohibits left and through movements from the side road, and provides a u-turn location downstream from the main crossing. This type of facility has been implemented for rural highways extensively in other states and has the potential to serve as a cost-effective solution to improve roadway safety within Nebraska. Comparative analysis is conducted for three site locations (Humphrey, Madison, and Dakota City, Nebraska) with either TWSC or AWSC existing geometry, analyzing the anticipated impacts of mitigation with a roundabout or an RCUT design. The costs and benefit analysis from implementing the various intersection geometries includes monetized delay costs, monetized crash costs, and anticipated construction costs. Alongside the cost benefit analysis, a decision matrix seeks to assess specifically whether an RCUT intersection would be appropriate, and the five factors for consideration identified include (1) the safety concerns at the location, (2) the overall levels of traffic demand, (3) the balance between major and minor movement traffic demand, (4) the presence of obstructions along the main roadway that would impact u-turn bay placement, and (5) the available space in the median for the u-turn bay.
Book Synopsis Field Evaluation of a Restricted Crossing U-turn Intersection by : Vaughan W. Inman
Download or read book Field Evaluation of a Restricted Crossing U-turn Intersection written by Vaughan W. Inman and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four-lane divided highways are an economical design solution to increase the capacity of rural highways compared to grade-separated limited access facilities. Compared to two-lane undivided rural highways, four-lane divided highways have markedly lower rates of sideswipe, rear-end, and head-on collisions. However, right-angle crash rates are markedly higher on four-lane divided highway intersections than at two-lane undivided highway intersections, largely as a result of left-turn and through movements from minor roads conflicting with far-side vehicles on the divided highway. The restricted crossing U-turn (RCUT) intersection is a promising treatment to mitigate right-angle crashes where two-lane minor roads intersect with rural four-lane divided highways. This report includes a comparison of operations at an RCUT intersection in Maryland with a roughly comparable conventional stop-controlled intersection on the same corridor. It also includes before-after crash analyses for intersections converted from conventional to RCUT designs on two Maryland highway corridors. The operational analysis found that conflicts between vehicles entering or crossing the highway from a minor road were reduced, weaving movements were about the same for the two intersection types, the RCUT design added about 1 min to travel time for vehicles making left-turn or through movements from the minor road. Three approaches were used to estimate the affect of an RCUT conversion on crashes. All three approaches led to the same conclusion: the RCUT design reduces crashes. A simple 3-year before and 3-year after analysis suggested a 30 percent decrease in the average number of crashes per year. An analysis that adjusted the observed crash rate at RCUT locations for the observed crash rate at nearby conventional intersections on the same corridors suggested a 28 percent decrease in the average annual number of crashes. An empirical Bayes analysis that adjusts for, among other things, the expected number of crashes at similar intersections and average annual traffic suggested a 44 percent decrease in crashes. Furthermore, the analyses suggest an overall reduction in crash severity with the RCUT design.
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 Restricted Crossing U-turn Intersection by :
Download or read book Restricted Crossing U-turn Intersection written by and published by . This book was released on 2014 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Evaluation of Unconventional Signalized Intersections on Arterial Roads and a Proposition for a Novel Intersection Design by : Ma'en Mohammad Ali Al-Omari
Download or read book Evaluation of Unconventional Signalized Intersections on Arterial Roads and a Proposition for a Novel Intersection Design written by Ma'en Mohammad Ali Al-Omari and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several unconventional intersection designs were proposed and implemented to enhance traffic safety and operation at intersections. The efficiency of these intersection designs was not sufficiently evaluated in the previous research because of the limited implementation of such designs. However, with the growing interest in the implementation of unconventional intersections by municipalities and transport agencies, it has become a need for a comprehensive evaluation of their safety and operational benefits. Therefore, this dissertation aims to evaluate the safety and operational aspects of unconventional intersection designs by employing different research approaches: crash analysis, microscopic simulation, and driving simulation. Firstly, this dissertation evaluated the effectiveness of median U-turn crossover-based intersections (median U-turn (MUT) and restricted crossing U-turn (RCUT) intersections), which have the least number of traffic conflicts among other unconventional intersection designs, in enhancing traffic safety by estimating crash modification factors (CMF) for their implementation. The results indicated that MUT and RCUT intersections are safer than the 4-leg conventional intersection. Secondly, A new innovative intersection design, which has been given the name "Shifting Movements" (SM) intersection, was introduced and proposed to replace the implementation of the RCUT intersection under moderate and heavy minor road traffic conditions. Evaluation of the operational benefits of this intersection design was performed in the microscopic simulation environment by assuming different traffic volume levels and left-turn proportions to represent the peak hour with moderate to high left-turn traffic volumes. The results demonstrated that the SM intersection design significantly outperforms conventional and RCUT intersections when they are subjected to high traffic volumes in terms of average control delay and throughput. Finally, A driving simulation experiment was conducted to evaluate the safety aspects of the SM intersection design. Several surrogate safety measures were adopted for the evaluation. The effectiveness of using infrastructure-to-vehicle (I2V) communication for mitigating the confusion at unconventional intersections has been also evaluated in this research. Findings indicated that RCUT and SM intersections have similar safety performance and crossing them is safer than crossing the 4-leg conventional intersection. It was found that using I2V communication is helpful in understanding unconventional movement patterns. This dissertation can be a solid reference for decision-makers regarding the implementation of unconventional intersection designs.
Book Synopsis Development of Zonal Safety Performance Functions for Local Road Intersections and Segments in Connecticut by : Ishraq Rayeed Ahmed
Download or read book Development of Zonal Safety Performance Functions for Local Road Intersections and Segments in Connecticut written by Ishraq Rayeed Ahmed and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Crash counts at a location are predicted using a Safety Performance Function (SPF) equation. The expected number of crashes on a traffic facility can be estimated using SPFs and the required countermeasures can be taken to reduce crashes in future. Due to the absence of sufficient traffic count data for local roads, new crash prediction approaches are essential to implementing highway safety improvement strategies. The study focuses on developing SPFs with coefficients varying by geographic covariate for segment and intersection crashes on local roads in Connecticut. Demographic and network topology data has been used as a surrogate for traffic count data which are not available for these roads. Two clustering methods – K-Means and Latent Class Clustering (LCC) has been explored for classifying cases for varying coefficients. The variables that were used to classify into clusters were land cover, population density and employment density. The models clustered using LCC with total population, retail and non-retail employment and average household income as independent variables were found to be the best based on model fit and out of sample prediction.
Book Synopsis Impacts of Access Management Techniques by : Jerome S. Gluck
Download or read book Impacts of Access Management Techniques written by Jerome S. Gluck and published by Transportation Research Board. This book was released on 1999 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Field Evaluation of a Restricted Crossing U-turn Intersection by :
Download or read book Field Evaluation of a Restricted Crossing U-turn Intersection written by and published by . This book was released on 2012 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Evaluation of Innovative Alternative Intersection Designs in the Development of Safety Performance Functions and Crash Modifications Factors by :
Download or read book Evaluation of Innovative Alternative Intersection Designs in the Development of Safety Performance Functions and Crash Modifications Factors written by and published by . This book was released on 2019 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to alleviate saftey and congestion problems, several types of intersections have been suggested and implemented in some states. This report aims to evaluate the alternative intersections that have been implemented in other states and predict their effects when they are implemented in Florida.
