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Evaluation Of Innovative Alternative Intersection Designs In The Development Of Safety Performance Functions And Crash Modifications Factors
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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.
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 Evaluation of Innovative Intersection Designs by : Ahmed Abdelrahman
Download or read book Safety Evaluation of Innovative Intersection Designs written by Ahmed Abdelrahman and published by . This book was released on 2020 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results showed that this alternative design could provide much benefits in terms of its operational performance. However, its poor safety performance could result in losses much higher than its benefits. The study concludes that DDIs could significantly decrease crash frequency, while DLTs could not provide safety benefits. However, DLTs might be more efficient for operational performance. It is recommended that appropriate safety countermeasures should be developed and implemented to enhance traffic safety at DLTs.
Book Synopsis Safety Evaluation of Multiple Strategies at Stop-controlled Intersections by : Thanh Le (Highway engineer)
Download or read book Safety Evaluation of Multiple Strategies at Stop-controlled Intersections written by Thanh Le (Highway engineer) and published by . This book was released on 2018 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Development of Crash Modification Factors program studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections. Improvements included basic signing and pavement markings. This strategy is intended to reduce the frequency and severity of crashes at stop-controlled intersections by alerting drivers to the presence and type of approaching intersection. Geometric, traffic, and crash data were obtained at three- and four-legged, two- and four-lane major road, and urban and rural stop-controlled intersections in South Carolina. To account for potential selection bias and regression to the mean, an empirical Bayesian before-after analysis was conducted, using reference groups of untreated intersections with similar characteristics to the treated sites. The analysis also controlled for changes in traffic volumes throughout time and time trends in crash counts unrelated to the treatments. The aggregate results indicate reductions for all crash types analyzed (i.e., total, fatal and injury, rear-end, right-angle, and nighttime). The reductions are statistically significant at the 95-percent confidence level for all crash types. For all crash types combined, the crash modification factors (CMFs) are 0.917 for all severities and 0.899 for fatal and injury crashes. The CMFs for rear-end, right-angle, and nighttime crashes are 0.933, 0.941, and 0.853, respectively. The benefit-cost ratio estimated with conservative cost and service life assumptions is 12.4 to 1 for total crashes at unsignalized intersections. The results suggest that the multiple low-cost treatments, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective.
Book Synopsis Procedure for Using Accident Modification Factors in the Highway Design Process by : James A. Bonneson
Download or read book Procedure for Using Accident Modification Factors in the Highway Design Process written by James A. Bonneson and published by . This book was released on 2007 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Highway safety is an ongoing concern to the Texas Department of Transportation (TxDOT). As part of its proactive commitment to improving highway safety, TxDOT is moving toward including quantitative safety analyses earlier in the project development process. The objectives of this research project are: (1) the development of safety design guidelines and evaluation tools to be used by TxDOT designers, and (2) the production of a plan for the incorporation of these guidelines and tools in the planning and design stages of the project development process. This document describes a procedure for using accident modification factors in the highway design process. Application of the procedure entails the use of several factors, where each factor addresses one specific design element (such as lane width, shoulder width, curve radius, etc.). Collectively, the factors can be used to estimate the effect of a change in one or more design elements. The procedure can be used to evaluate the safety benefits associated with alternative geometric designs.
Book Synopsis Safety Evaluation of Multiple Strategies at Stop-controlled Intersections by : Thanh Le
Download or read book Safety Evaluation of Multiple Strategies at Stop-controlled Intersections written by Thanh Le and published by . This book was released on 2017 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Technical summary of the FHA report FHWA-HRT-17-086 program that studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections.
Book Synopsis Safety Performance of Rural Intersections with Atypical Design Characteristics by : Anthony Ingle
Download or read book Safety Performance of Rural Intersections with Atypical Design Characteristics written by Anthony Ingle and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results described in this dissertation represent a culmination of the efforts in the study of safety performance at rural intersections with atypical design characteristics. The specificity of this topic does not limit its relevance to intersection safety and the science of relating infrastructure traits to failure risks. Statistical modelling is used to predict average crash frequency. The model specification uses attributes such as the average annual daily traffic (AADT) on the major and minor road approaches, among other characteristics, to account for the exposure to crashes of various defined types and severities.The atypical intersection geometries studied herein consist of offset-T, curved corner, highly skewed, and multi-leg with five or more intersection legs. All of the intersections studied are minor road stop-controlled, along two-lane two-way rural highways. An effort is made to summarize the outcomes in practically applicable terminology such as Crash Modification Factors (CMFs) so that the conclusions of this study can lend toward a safer transportation future.The investigation into offset-T intersections utilizes a series of random intercept negative binomial models for crash occurrence that was generated based on 10 years of crash data from a sample of 299 offset-T intersections and 301 four-leg intersections with minor stop-control along rural two-lane highways in Michigan. The search for candidate intersections was exhaustive, considering that both major and minor road AADT was desired for each site. The modeling technique used a random effect for each site (location). Models were developed for total (non-animal) intersection crashes, as well as for single motor vehicle, angle, and rear-end crash types. The effects of offset distance and direction were analyzed and incorporated into the models. Compared to conventional four-leg intersections, offset-T intersections exhibited 35 percent more crashes regardless of the offset distance or direction. Considering crash types, single motor vehicle crashes occurred more frequently at offset-T intersections, and increased as the offset distance increased. Rear end crashes also occurred more frequency at offset-T intersections, with left offsets having more crash occurrence than right offsets. However, angle crashes are 40 to 69 percent lower at offset-T intersections due to the elimination of the direct crossing maneuver. The CMF for converting an existing offset-T into a conventional four-leg intersection is 0.74 within the studied ranges of offset direction and distance. This equivalates to a 26 percent reduction in total (non-animal) crash frequency. At curved corner intersections, a random intercept negative binomial models for crash occurrence used geographic region as a random effect. A total intersection crash (non-animal) model was generated based on 10 years of crash data from a sample of 227 three-leg sites and 65 four-leg sites among curved corner intersection geometry only. Reliance on the availability of minor road AADT so severely limited the sample population that an estimation of minor road AADT was made in order to proceed with modeling. A minor road AADT estimation model uses national functional classification as well as surface type, population density, and major road traffic volume to estimate the minor road traffic. A table of CMFs is presented for potentially converting an existing configuration into a combined/merged approach that is consistent with a traditional countermeasure from MDOT Geometric Design Guidelines. At curved corner intersections, installing a combined/merged intersection approach near the midpoint of the curve is a potential countermeasure that can be expected to reduce the average intersection crash frequency by 25 percent for three-leg configurations. A larger radius of curvature along the curved segment at these types of intersections is also very favorable for safety performance. Each 100-foot increase in the radius of a three-leg or four-leg curved corner intersection is estimated to reduce crash occurrence by 5 percent and 8 percent respectively.The safety influence of intersection skew angle on rural two-lane two-way facilities was evaluated by calibrating crash modification factors. Ten years of crash history among federal aid and non-federal aid highways was used to develop crash modification functions at three-leg and four-leg stop-controlled intersections. Skew angle was investigated as a parameter in the SPF models both as a continuous variable, with observed values ranging from 0 to 80 degrees, and categorized into ranges. A few transformations of the skew parameter were considered such as the flexible form model having skew interaction with AADT (annual average daily traffic), and a Hoerl curve. Both three-leg and four-leg intersections exhibited an initially increasing trend of crash rates followed by a decreasing trend as skew angle increased. A categorical model was found to best describe the skew relationship using discrete skew angle ranges. Among three-leg intersections, a skew angle between 17 to 27 degrees experienced 22 percent more crashes than perpendicular intersections. However, more highly skewed three-leg intersections exhibited a decreasing relationship to increasing skew angle. Among four-leg intersections, a skew angle between 17 to 27 degrees experienced 40 percent more crashes, while intersections with a skew angle greater than 45 degrees did not have significantly different crash occurrence than perpendicular intersections. The implications of assuming a monotonic increasing relationship to skew angle are challenged as a result of this study. Multi-leg intersections with more than four approach legs constitute a rare circumstance, yet these sites experience higher than average crash frequencies compared to conventional four-leg intersections. Single-vehicle as well as angle and rear-end crash types are most likely to occur at multi-leg intersections based on the history of crashes observed.The procedures described in this study are consistent with the Highway Safety Manual (HSM) and subsequent state of the art research for the procurement of safety performance models for any variety of circumstances. By utilizing an expansive data set and geospatial mapping techniques, the analysis is extended to previously unexplored site types. The extension of predictive safety analysis to atypical intersection types with unique geometric characteristics helps to fill a gap in the current field of practice with the hope of achieving an ultimate goal toward zero deaths in motor vehicle transportation.
Book Synopsis Role and Application of Accident Modification Factors in the Highway Design Process by : James A. Bonneson
Download or read book Role and Application of Accident Modification Factors in the Highway Design Process written by James A. Bonneson and published by . This book was released on 2005 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Operational and Safety Performance Assessment of Innovative Intersection and Interchange Designs in a Connected Vehicle Environment by : Mutasem Alzoubaidi
Download or read book Operational and Safety Performance Assessment of Innovative Intersection and Interchange Designs in a Connected Vehicle Environment written by Mutasem Alzoubaidi and published by . This book was released on 2022 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Innovative intersections and interchange designs is one strategy known to enhance the operational and safety performance of our roads. Innovative designs specifically lead to an improved signal progression and result in reduced travel times, delays, crash severities and frequencies. Connected Vehicle (CV) technology is another strategy that has enabled dozens of Intelligent Transportation Systems (ITS) applications with the potential to bring major safety, mobility and environmental benefits. Many studies have focused on exploring each strategy when implemented solely. Therefore, one of the goals of this dissertation is studying the impacts and benefits of the combined implementation of the two strategies, while the other lies within developing a new innovative interchange design called the Continuous Green-T Partial Cloverleaf A (CGT-parclo A) and exploring its operational and safety aspects. A microsimulation approach was followed to achieve these goals.The results show that the combined implementation of CVs and innovative intersections has reduced travel times, and delays by nearly 65.3%, and 29.2%, respectively. Additionally, the total number of conflicts, rear-end and lane change conflicts dropped by nearly 23.8%, 23.6% and 24.4%, respectively at full Continuous Flow Intersections and 100% MPRThe CGT-parclo A exhibited superior operational performance to a multitude of interchange designs in most tested cases. The CGT-parclo A reduced travel times, and delays as high as 55.7%, and 69.8%, respectively, compared to the parclo A and parclo progressA. The CGT-parclo A is the best form of parclo A interchanges in terms of reducing the likelihoods, severities and frequencies of crashes.
Book Synopsis Effectiveness Evaluation of a Modified Right-turn Lane Design at Intersections by : Kerrie Schattler
Download or read book Effectiveness Evaluation of a Modified Right-turn Lane Design at Intersections written by Kerrie Schattler and published by . This book was released on 2016 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of a Safety Evaluation Procedure for Identifying High-risk Signalized Intersections in the Virginia Department of Transportation's Northern Virginia District by : Young-Jun Kweon
Download or read book Development of a Safety Evaluation Procedure for Identifying High-risk Signalized Intersections in the Virginia Department of Transportation's Northern Virginia District written by Young-Jun Kweon and published by . This book was released on 2007 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research was undertaken to develop an evaluation procedure to identify high-risk four-legged signalized intersections in VDOT's Northern Virginia district by traffic movements and times of day. By using the developed procedure, traffic engineers are expected to be able to identify signalized intersections where the traffic crash occurrences under different traffic conditions for different times of day are more frequent than would normally be expected. Using generalized linear models such as negative binomial models, one safety performance function was estimated for each of nine crash population reference groups formed by three traffic crash patterns (crash patterns 1, 4, and 6) and four times of day (A.M. peak, mid day, P.M. peak, and evening off peak). Crash pattern 1 is a same-direction crash (rear-end, sideswipe or angle crash) that occurs after exiting the intersection; crash pattern 4 is a right-angle crash between two adjacent straight-through vehicle movements in the intersection; and crash pattern 6 is an angle or head-on or opposite sideswipe crash between a straight-through vehicle movement and an opposing left-turn vehicle movement in the intersection. The procedure developed in this study is based on the empirical Bayes (EB) method. Additional data do not need to be collected in order to use the EB procedure because all the data required for applying the EB procedure should be obtainable from VDOT's crash database and from Synchro input data that are already available to traffic engineers for traffic signal phase plans. Thus, the EB procedure is cost-effective and readily applicable. For easy application of the EB procedure, an EB spreadsheet was developed using Microsoft Excel, and a users' guide was prepared. These are available from the author upon request.
Book Synopsis Evaluation of Safety Strategies at Signalized Intersections by : Raghavan Srinivasan
Download or read book Evaluation of Safety Strategies at Signalized Intersections written by Raghavan Srinivasan and published by Transportation Research Board. This book was released on 2011 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB’s National Cooperative Highway Research Program (NCHRP) Report 705: Evaluation of Safety Strategies at Signalized Intersections explores crash modification factors (CMFs) for safety strategies at signalized intersections. CMFs are a tool for quickly estimating the impact of safety improvements.
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 Report on the Railroad Technology Program, by the Secretary of Transportation to the President, the Senate, and the House of Representatives by : United States. Dept. of Transportation
Download or read book Report on the Railroad Technology Program, by the Secretary of Transportation to the President, the Senate, and the House of Representatives written by United States. Dept. of Transportation and published by . This book was released on 1974 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Intersection and Interchange Design by : National Research Council (U.S.). Transportation Research Board
Download or read book Intersection and Interchange Design written by National Research Council (U.S.). Transportation Research Board and published by . This book was released on 1993 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Report on the Railroad Technology Program, by the Secretary of Transportation to the President, the Senate, and the House of Representatives by : United States. Department of Transportation
Download or read book Report on the Railroad Technology Program, by the Secretary of Transportation to the President, the Senate, and the House of Representatives written by United States. Department of Transportation and published by . This book was released on 1973 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
