Evaluating The Effects Of Prohibiting Left Turns And The Resulting U Turn Movement

Author : Mashrur A. Chowdhury
Publisher :
ISBN 13 :
Total Pages : 90 pages
Book Rating : 4.59/5 ( download)

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Download or read book Evaluating the Effects of Prohibiting Left Turns and the Resulting U-turn Movement written by Mashrur A. Chowdhury and published by . This book was released on 2003 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research was to evaluate the operational and safety effects of restricting direct left turns from a driveway and providing alternatives to accommodate the left turn deterred traffic. This study was conducted in three phases: survey of state agencies, operational analysis, and safety assessment. Very little operational difference was found between no restrictions on direct left turns versus the restrictions with the U-turn alternative movements from site to site. While changes in the traffic volumes on the mainline had an impact in specific instances, no definite trends were apparent. As a result of all findings in this study, it is proposed that alternatives must be evaluated on a site-by-site basis. This study also found the jughandle design to be a superior alternative for accommodating left-turn deterred traffic for multi-lane divided and undivided sites compared to mid-block or intersection U-turns. The safety assessment revealed that a right turn followed by a U-turn movement is safer than the direct left turn.

Author :
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.11/5 ( download)

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Download or read book Operational Evaluation of Right Turns Followed by U-turns at Signalized Intersections (6 Or More Lanes) as an Alternative to Direct Left Turns written by and published by . This book was released on 2005 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Pan Liu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.55/5 ( download)

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Download or read book Evaluation of the Operational Effects of U-turn Movement written by Pan Liu and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: In Florida, the increased installation of non-traversable medians and directional median opening has produced an increased number of U-turns on multilane highways. Arguments have been advanced by some opponents of median modification projects that the increased numbers of U-turns may result in safety and operational problems on multilane highways. The primary objective of this study is to evaluate the operational effects of U-turn movement on multilane roadways. To achieve this research objective, extensive data were collected. Field measurements were conducted at 40 sites in the Tampa Bay area of Florida to collect traffic operations data. Besides, the crash histories of 179 selected roadway segments in central Florida were investigated. Statistical analysis was conducted based on the collected traffic operations data and crash data to quantitatively evaluate the operational performance of U-turn movement. Delay and travel time were compared for different driveway left-turn alternatives that are widely used in Florida and nationally. Crash rate models were developed to evaluate how the separation distance between a driveway exit and the downstream U-turn bay impacts the safety performance of vehicles making right-turns followed by U-turns (RTUT). With the crash data analysis results, the minimum separation distances under different roadway conditions were determined to facilitate driver use of RTUTs. The capacity of U-turn movement was analyzed under two different situations: (1) U-turns are provided at a signalized intersection; and (2) U-turns are provided at an unsignalized intersection. Adjustment factors were developed to quantify the impacts of the presence of U-turning vehicles on the capacity of a signalized intersection. The critical gaps and follow-up time for U-turn movement at unsignalized intersections were estimated. With the estimated critical gaps and follow-up time, the Harders model was used to determine the capacity of U-turn movement at an unsignalized intersection. This study also looks extensively at the minimum roadway width and median width required by vehicles to perform U-turn maneuvers on 4-lane divided roadways. It was found that a roadway width of 46 ft is generally sufficient for most types of design vehicles (except heavy vehicles) to perform a continuous U-turn maneuver without impedance.

Author :
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.89/5 ( download)

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Download or read book Safety Evaluation of Right Turns Followed by U-turns as an Alternative to Direct Left Turns: Operational evaluation of right turns followed by U-turns as an alternative to direct left turns written by and published by . This book was released on 2001 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Jian John Lu
Publisher :
ISBN 13 :
Total Pages : 260 pages
Book Rating : 4.03/5 ( download)

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Download or read book Safety Evaluation of Right Turns Followed by U-turns (4 Lanes Arterials) as an Alternative to Direct Left Turns written by Jian John Lu and published by . This book was released on 2005 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Xiaodong Wang
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.02/5 ( download)

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Download or read book Effects of U-turns on Capacity at Signalized Intersections and Simulation of U-turning Movement by Synchro written by Xiaodong Wang and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The primary objective of this study is to evaluate the operational effects of U-turn movement at signalized intersections. More specifically, the research objectives include the following parts: To identify the factors affecting the operational performance of U-turning vehicles. In this case, we are particularly interested in the U-turn speeds of U-turning vehicles; To evaluate the impacts of U-turns on capacity of signalized intersections, and; To simulate U-turn movement at signalized intersections using Synchro and validate the simulation results. To achieve the research objectives, extensive field data collection work was conducted at sixteen selected sites at Tampa Bay area of Florida. The data collected in the field include: U-turning speed; Left turning speed; Turning radius Queue discharge time; Control delay; Hourly traffic volume, and; Percentage of U- turning vehicles in left turn lane. Based on the collected field data, a linear regression model was developed to identify the factors affecting the turning speeds of U-turning vehicles at signalized intersections. The model shows the turning speed is significantly impacted by the turning radius and the speed of U-turning vehicles increases with the increase of turning radius. On the basis of field data field data collection, a regression model was developed to estimate the relationship between the average queue discharge time for each turning vehicle and the various percentages of U-turning vehicles in the left turn traffic stream. Adjustment factors for various percentages of U-turning vehicles were also developed by using the regression model. The adjustment factors developed in this study can be directly used to estimate the capacity reduction due to the presence of various percentages of U-turning vehicles at a signalized intersection. The developed adjustment factors were used to improve the simulation of U-turn movement at signalized intersection by using Synchro. The simulation model was calibrated and validated by field data. It was found that using the developed adjustment factors will greatly improve the accuracy of the simulation results for U-turn movement.

Author : Jian John Lu
Publisher :
ISBN 13 :
Total Pages : 158 pages
Book Rating : 4.05/5 ( download)

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Download or read book Safety Evaluation of Right Turns Followed by U-turns as an Alternative to Direct Left Turns: Crash data analysis written by Jian John Lu and published by . This book was released on 2001 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Xinyun Cao
Publisher :
ISBN 13 : 9781321207545
Total Pages : 77 pages
Book Rating : 4.49/5 ( download)

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Download or read book A Performance Accessment of the Elimination of Left-turns at Selected Intersections written by Xinyun Cao and published by . This book was released on 2014 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: For most signalized intersections, left-turn movements are considered as a primary contributor to intersection delay. The concept of eliminating left-turn movements is now feasible with the rise of GPS-based routing which will allow the active routing of vehicles in networks with reduced left turns. This research seeks to estimate the impact of left turn reductions on overall travel time and left turn delay at intersections. The research objective is to evaluate the effect of left turn movement elimination in sample networks. The type of intersections considered is restricted to a grid network but is defined by the roadway hierarchy. A sample network was selected based on a real world network and reflecting observed volumes, travel times, and delays. The analysis approach is to eliminate left turn movements in three types of intersections by applying turn prohibitions and adjusting cycle lengths and turn penalties on other movements. Network performance is then assessed based on delay reduction, total travel time, and fuel consumption. It was concluded that selective reduction of left turn movements can improve network performance.

Author : Lu, Jian John Lu
Publisher :
ISBN 13 :
Total Pages : 172 pages
Book Rating : 4.95/5 ( download)

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Download or read book Safety Evaluation of Right Turns Followed by U-turns at Signalized Intersections (6 Or More Lane Arterials) as an Alternative to Direct Left Turns written by Lu, Jian John Lu and published by . This book was released on 2005 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Jian John Lu
Publisher :
ISBN 13 :
Total Pages : 194 pages
Book Rating : 4.16/5 ( download)

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Download or read book Determination of the Offset Distance Between Driveway Exits and Downstream U-turn Locations for Vehicles Making Right Turns Followed by U-turns written by Jian John Lu and published by . This book was released on 2005 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Florida increasingly uses restrictive medians and directional median openings on multi-lane highways to manage left turn egress maneuvers from driveways and side streets. By installing non-traversable medians and replacing full median openings with directional median openings at various locations, Florida prohibits direct left-turn exits onto some major arterials. The purpose of this research was to evaluate how the offset distance between driveway exits and downstream median openings or signalized intersections impacts traffic operational and safety performance. The primary objective is to determine optimum offset distances to facilitate driver use of Right Turn Followed by a U-Turn (RTUT) maneuvers, specifically investigating (1) traffic operational performance, based on the evaluation of vehicle travel time at various offset distances, and (2) safety performance, based on the evaluation of traffic conflicts and crash data. The focus of this research was on urban or suburban multi-lane divided arterials. Researchers studied the impacts of offset distance under four different scenarios: 4-lane divided roadways accommodating U-turns at median openings, 4-lane divided roadways accommodating U-turns at signalized intersections, 6 or more-lane divided roadways accommodating U-turns at median openings, and 6 or more-lane divided roadways accommodating U-turns at signalized intersections.