High Volume, Heavy Vehicle, and Bus Stop Impacts on Four-lane to Three-lane Conversion PDF Download

Author: Woochul Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 164

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Author: Keith K. Knapp
Publisher:
ISBN:
Category : Left-turn lanes
Languages : en
Pages : 112

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Book Description
At and above 1,750 vehicles per hour, the simulation indicated a reduction in arterial level of service. Therefore, at least in Iowa, the feasibility of a four-lane undivided to three-lane conversion should be questioned and/or considered much more closely when a roadway has (or is expected to have) a peak-hour volume of more than 1,750 vehicles. Assuming that 10 percent of the daily traffic occurs during the peak-hour, these volume recommendations would correspond to 15,000 and 17,500 vehicles per day, respectively. These suggestions, however, are based on the results from one idealized case xi study corridor analysis. Individual operational analysis and/or simulations should be completed in detail once a four-lane undivided to three-lane cross section conversion is considered feasible (based on the general suggestions above) for a particular corridor. All of the simulations completed as part of this project also incorporated the optimization of signal timing to minimize vehicle delay along the corridor. A number of determination feasibility factors were identified from a review of the past research, before-and-after case study results, and the simulation sensitivity analysis. The existing and expected (i.e., design period) statuses of these factors are described and should be considered. The characteristics of these factors should be compared to each other, the impacts of other potentially feasible cross section improvements, and the goals/objectives of the community. The factors discussed in these guidelines include - roadway function and environment - overall traffic volume and level of service - turning volumes and patterns - frequent-stop and slow-moving vehicles - weaving, speed, and queues - crash type and patterns - pedestrian and bike activity - right-of-way availability, cost, and acquisition impacts - general characteristics, including - parallel roadways - offset minor street intersections - parallel parking - corner radii - at-grade railroad crossings xii The characteristics of these factors are documented in these guidelines, and their relationship to four-lane undivided to three-lane cross section conversion feasibility identified. This information is summarized along with some evaluative questions in this executive summary and Appendix C. In summary, the results of past research, numerous case studies, and the simulation analyses done as part of this project support the conclusion that in certain circumstances a four-lane undivided to three-lane conversion can be a feasible alternative for the mitigation of operational and/or safety concerns. This feasibility, however, must be determined by an evaluation of the factors identified in these guidelines (along with any others that may be relevant for a individual corridor). The expected benefits, costs, and overall impacts of a four-lane undivided to three-lane conversion should then be compared to the impacts of other feasible alternatives (e.g., adding a raised median) at a particular location.

Author: Karen Lynn Giese
Publisher:
ISBN:
Category :
Languages : en
Pages : 144

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This study investigated and compared the simulated operational measures of effectiveness for similar traffic volumes, left-turn percentages, and access point densities for a case study roadway with a four-lane undivided and a three-lane cross section. The objective of this study was to quantify the operational impacts of this type of conversion. Actual four- lane undivided to three-lane conversions have shown decreased crashes and crash rates, produced small reductions in average arterial travel speed (similar to the CORSIM results), and resulted in large reductions in the number of speeding vehicles. Four analysis tools were reviewed and the CORSIM model was chosen to complete a sensitivity analysis that included five simulations for each combination of four average daily traffic levels, three left-turn volumes, and six access point densities. The arterial level of service (LOS) decreased from LOS C to D when the average daily traffic was 20,000 vehicles per day (the largest volume considered). The timing of the two-phase signalized intersections within the simulated corridor was optimized and did not experience a change of more than 5.5 seconds per vehicle in average stopped delay (i.e., no overall intersection LOS change). In general, a statistically significant difference in average arterial travel speed was found when four-lane undivided roadways were compared to similar three-lane roadways. The magnitude of the difference, however, ranged only from 0.5 to 3.9 miles per hour.

Author: Thomas M. Welch
Publisher:
ISBN:
Category : Left-turn lanes
Languages : en
Pages : 34

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In recent years, many traffic engineers have advocated converting four-lane undivided urban streets to three-lane two-way left turn facilities. A number of these conversions have been successfully implemented. Accident rates have decreased while corridor and intersection levels of service remained acceptable. This conversion concept is yet another viable alternative "tool" to place in our urban safety/congestion toolbox.

Author:
Publisher: AASHTO
ISBN: 1560512598
Category : Technology & Engineering
Languages : en
Pages : 138

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Context-sensitive solutions (CSS) reflect the need to consider highway projects as more than just transportation facilities. Depending on how highway projects are integrated into the community, they can have far-reaching impacts beyond their traffic or transportation function. CSS is a comprehensive process that brings stakeholders together in a positive, proactive environment to develop projects that not only meet transportation needs, but also improve or enhance the community. Achieving a flexible, context-sensitive design solution requires designers to fully understand the reasons behind the processes, design values, and design procedures that are used. This AASHTO Guide shows highway designers how to think flexibly, how to recognize the many choices and options they have, and how to arrive at the best solution for the particular situation or context. It also strives to emphasize that flexible design does not necessarily entail a fundamentally new design process, but that it can be integrated into the existing transportation culture. This publication represents a major step toward institutionalizing CSS into state transportation departments and other agencies charged with transportation project development.

Author: Lee August Rodegerdts
Publisher: Transportation Research Board
ISBN: 0309155118
Category : Technology & Engineering
Languages : en
Pages : 407

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TRB's National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide - Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts. This report updates the U.S. Federal Highway Administration's Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.

Author: J. E. Curren
Publisher: Transportation Research Board
ISBN: 9780309053693
Category : Technology & Engineering
Languages : en
Pages : 92

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Author:
Publisher: AASHTO
ISBN: 1560512717
Category : CD-ROMS.
Languages : en
Pages : 142

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Author: Ken Skorseth
Publisher:
ISBN:
Category : Gravel roads
Languages : en
Pages : 112

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The purpose of this manual is to provide clear and helpful information for maintaining gravel roads. Very little technical help is available to small agencies that are responsible for managing these roads. Gravel road maintenance has traditionally been "more of an art than a science" and very few formal standards exist. This manual contains guidelines to help answer the questions that arise concerning gravel road maintenance such as: What is enough surface crown? What is too much? What causes corrugation? The information is as nontechnical as possible without sacrificing clear guidelines and instructions on how to do the job right.

Author: Gary A. Davis
Publisher:
ISBN:
Category : Roads
Languages : en
Pages : 0

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A 4-3 conversion involves changing a four-lane undivided road into one with two general travel lanes separated by a two-way left turn lane. A commonly-used guideline states that a 4-3 conversion can be considering as long as the road’s average annual daily traffic (AADT) volume does not exceed 15,000 vehicles/day but opinions vary, from lowering the AADT threshold to 10,000 vehicles/day to anecdotal evidence for successful 4-3 conversions with AADTs as high as 20,000. The main objective of this project was to identify conditions where 4-3 conversions might be feasible at AADTs greater than 15,000. After reviewing the literature, we conducted simulation studies on three different roads to identify combinations of major and minor road flow where three-lane configurations provided acceptable levels of service. Eight intersections, with 16 approaches, were then selected to represent our findings. These results were presented as summary tables that practitioners could use to make initial assessments regarding 4-3 conversion feasibility.