Impacts On Safety Of Left Turn Treatment At High Speed Signalized Intersections
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Impacts On Safety Of Left Turn Treatment At High Speed Signalized Intersections
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Author : T. H. Maze
language : en
Publisher:
Release Date : 1994
Impacts On Safety Of Left Turn Treatment At High Speed Signalized Intersections written by T. H. Maze and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with Left-turn lanes categories.
Left-turning traffic is a major source of conflicts at intersections. Though an average of only 10% to 15% of all approach traffic turns left, these vehicles are involved in approximately 45% of all accidents. This report presents the results of research conducted to develop models which estimate approach accident rates at high speed signalized intersections. The objective of the research was to quantify the relationship between traffic and intersection characteristics, and accident potential of different left turn treatments. Geometric, turning movement counts, and traffic signal phasing data were collected at 100 intersections in Iowa using a questionnaire sent to municipalities. Not all questionnaires resulted in complete data and ultimately complete data were derived for 63 intersections providing a database of 248 approaches. Accident data for the same approaches were obtained from the Iowa Department of Transportation Accident Location and Analysis System (ALAS). Regression models were developed for two different dependent variables: 1) the ratio of the number of left turn accidents per approach to million left turning vehicles per approach, and 2) the ratio of accidents per approach to million traffic movements per approach. A number of regression models were developed for both dependent variables. One model using each dependent variable was developed for intersections with low, medium, and high left turning traffic volumes. As expected, the research indicates that protected left turn phasing has a lower accident potential than protected/permitted or permitted phasing. Left turn lanes and multiple lane approaches are beneficial for reducing accident rates, while raised medians increase the likelihood of accidents. Signals that are part of a signal system tend to have lower accident rates than isolated signals. The resulting regression models may be used to determine the likely impact of various left turn treatments on intersection accident rates. When designing an intersection approach, a traffic engineer may use the models to estimate the accident rate reduction as a result of improved lane configurations and left turn treatments. The safety benefits may then be compared to any costs associated with operational effects to the intersection (i.e., increased delay) to determine the benefits and costs of making intersection safety improvements.
Capacity And Operational Effects Of Midblock Left Turn Lanes
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Author : James A. Bonneson
language : en
Publisher: Transportation Research Board
Release Date : 1997
Capacity And Operational Effects Of Midblock Left Turn Lanes written by James A. Bonneson and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with Technology & Engineering categories.
The objective of this research project was to develop a methodology for evaluating alternative midblock left-turn treatments on urban and suburban arterials. The methodology had to be applicable to three common midblock left-turn treatments: the raised-curb median, the flush median with two-way left-turn lane (TWLTL) delineation, and the undivided cross section. The methodology developed for this research focuses on the evaluation of midblock street segments on urban and suburban arterials. The basis for NCHRP Report 395.
Signalized Intersections
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Author : Lee August Rodegerdts
language : en
Publisher:
Release Date : 2004
Signalized Intersections written by Lee August Rodegerdts and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Roads categories.
This guide provides a single, comprehensive document with methods for evaluating the safety and operations of signalized intersections and tools to remedy deficiencies. The treatments in this guide range from low-cost measures such as improvements to signal timing and signage, to high-cost measures such as intersection reconstruction or grade separation. Topics covered include fundamental principles of user needs, geometric design, and traffic design and operation; safety and operational analysis techniques; and a wide variety of treatments to address existing or projected problems, including individual movements and approaches, pedestrian and bicycle treatments, and corridor techniques. It also covers alternative intersection forms that improve intersection performance through the use of indirect left turns and other treatments. Each treatment includes a discussion of safety, operational performance, multimodal issues, and physical and economic factors that the practitioner should consider. Although the guide focuses primarily on high-volume signalized intersections, many treatments are applicable for lower volume intersections as well. The information contained in this guide is based on the latest research available on treatments and best practices in use by jurisdictions across the United States. Additional resources and references are highlighted for the student, practitioner, researcher, or decisionmaker who wishes to learn more about a particular subject.
Low Cost Safety Enhancements For Stop Controlled And Signalized Intersections
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Author :
language : en
Publisher:
Release Date : 2009
Low Cost Safety Enhancements For Stop Controlled And Signalized Intersections written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Roads categories.
"The purpose of this document is to present information on suggested effective, low-cost intersection countermeasures developed using intersection safety research results and input from an intersection safety expert panel. These low-cost countermeasures can be applied to a large number of intersections with a high frequency of crashes using a systematic approach. The net impact of such an approach can produce significant reductions in statewide intersection crashes, fatalities, and serious injuries. Low-cost countermeasures are defined as those ranging from $1,000 to $50,000 per intersection"--Page 4
Guidelines For Right Turn Treatments At Unsignalized Intersections And Driveways
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Author : Tanweer Hasan
language : en
Publisher:
Release Date : 1996
Guidelines For Right Turn Treatments At Unsignalized Intersections And Driveways written by Tanweer Hasan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with Driveways categories.
Guidelines for right-turn treatments at unsignalized intersections and driveways on the state highway system of Kansas were developed in this study. Two types of treatments, full-width lane and taper, were considered over the do-nothing radius treatment. THe guidelines were based on the results of an economic analysis conducted over a wide range of traffic volumes and speeds. A simple model was developed to determine the operational effects of right-turn movements at unsignalized intersections and driveways on high-speed highways. The operational effects were estimated in terms of delay and excess fuel consumption experienced by through vehicles due to the right turns. The relationship between speed differential and accidents was used to estimate the reduction in right-turn same direction rear-end accidents that would be expected to result from the provision of a right-turn treatment. Comparison with other guidelines and validation of existing right-turn treatments at the study sites indicate that the range of the guidelines developed in this study isre reasonable. They are also more definitive because they consider highway operating speed. They are more flexible in determining an appropriate treatment because an intermediate taper treatment is considered.
Safety Effectiveness Of Intersection Left And Right Turn Lanes
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Author : Douglas W. Harwood
language : en
Publisher:
Release Date : 2002
Safety Effectiveness Of Intersection Left And Right Turn Lanes written by Douglas W. Harwood and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Roads categories.
This report presents the results of research that performed a well-designed before-after evaluation of the safety effects of providing left- and right-turn lanes for at-grade intersections. Geometric design, traffic control, traffic volume, and traffic accident data were gathered for a total of 280 improved intersections, as well as 300 similar intersections that were not improved during the study period. The types of improvement projects evaluated included installation of added left-turn lanes, added right-turn lanes, and extension of the length of existing left- or right-turn lanes. An observational before-after evaluation of these projects was performed using several alternative evaluation approaches. The three contrasting approaches to before-after evaluation used were the yoked comparison or matched-pair approach, the comparison group approach, and the Empirical Bayes approach. The research not only evaluated the safety effectiveness of left- and right-turn lane improvements, but also compared the performance of these three alternative approaches in making such evaluations. The research developed quantitative safety effectiveness measures for installation design improvements involving added left-turn lanes and added right-turn lanes. The research concluded that the Empirical Bayes method provided the most accurate and reliable results. Further use of this method is recommended.
Left Turn Treatments At Intersections
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Author : James L. Pline
language : en
Publisher: Transportation Research Board
Release Date : 1996
Left Turn Treatments At Intersections written by James L. Pline and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with Controlled access highways categories.
This synthesis will be of interest to traffic engineers in both the public and private sectors, as well as to design engineers, safety and law enforcement officials, traffic signal technicians, and others concerned with the accommodation of nonmotorized transportation (pedestrians and bicycles) on the roadway. The synthesis describes the traffic conditions, signalization, signing, and geometric design issues associated with accommodating left-turning vehicles at intersections. This report of the Transportation Research Board discusses the basic concerns related to left-turn movements and the guidelines and requirements for handling these movements in the traffic stream. It also addresses the design criteria for left-turn treatments and the performance measures frequently applied to determine their effectiveness. The synthesis discusses the specific requirements for signing and pavement markings, and the various elements of traffic signal requirements, signal design and installation, phasing optimization, and lane-use controls. There is also a description of special applications such as U-turn control, pedestrian requirements, bicycles, and light rail transit interface.
Toolbox To Assess Tradeoffs Between Safety Operations And Air Quality For Intersection And Access Management Strategies
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Author :
language : en
Publisher:
Release Date : 2008
Toolbox To Assess Tradeoffs Between Safety Operations And Air Quality For Intersection And Access Management Strategies written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Air quality categories.
Significant transportation agency resources are allocated to meet maintenance, operations, safety, and air quality goals. Although there is a significant amount of overlap between these areas, decisions to meet agency goals in one area often do not consider goals in the others and, as a result, miss opportunities to leverage funds and make better informed decisions overall. There are a number of areas of overlap between capital improvements designed to improve operations, maintenance, safety, and air quality goals that provide a rich opportunity to leverage funds and use resources more cost-effectively while meeting agency goals in two or more of the areas. The objective of this research is to develop analytical tools that can efficiently evaluate common capital projects used to meet agency goals in one area (operations, safety, air quality, and maintenance) but that also have a significant impact on the others.
Development Of Left Turn Lane Guidelines For Signalized And Unsignalized Intersections
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Author :
language : en
Publisher:
Release Date : 2004
Development Of Left Turn Lane Guidelines For Signalized And Unsignalized Intersections written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Left-turn lanes categories.
It is generally accepted that the level of service (LOS) at intersections significantly affects the overall LOS of the road system. It is also known that the LOS at an intersection can be adversely affected by frequently allowing left-turning vehicles to block through traffic. In addition, crash rates tend to be higher at intersections than on through sections of a road. The separation of left-turning vehicles from through traffic is therefore an important condition for the safe and effective operation of intersections. Existing guidelines for installing left-turn lanes have several limitations. They are mainly based on the traffic volumes at the intersection, and they use deterministic models with fixed gap acceptance and/or left-turn maneuver times. In addition, the guidelines for left-turn lanes for unsignalized intersections and signalized intersections must be specific for the type of intersection. In this study, new left-turn guidelines for both unsignalized and signalized intersections were developed on the basis of well-validated event-based simulation programs. Guidelines for unsignalized intersections were based on the percentage of left turns blocking through vehicles, whereas the guidelines for signalized intersections were developed using a minimum left-turn volume of either 85% left-turn capacity or LOS E delay (55 seconds/vehicle). In addition to the general guidelines, a prioritization tool that can be used to prioritize candidate intersections was developed. The prioritization tool accounts for both operational and safety aspects.
Evaluation Of Safety Strategies At Signalized Intersections
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Author : Raghavan Srinivasan
language : en
Publisher: Transportation Research Board
Release Date : 2011
Evaluation Of Safety Strategies At Signalized Intersections written by Raghavan Srinivasan and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Technology & Engineering categories.
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.