Evaluation of Traffic Signal Displays for Protected/permissive Left-turn Control PDF Download

Author: Christopher Lynn Brehmer
Publisher: Transportation Research Board
ISBN: 0309087570
Category : Information display systems
Languages : en
Pages : 94

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Author: Chris L. Brehmer
Publisher:
ISBN: 9780309087575
Category : Highway research
Languages : en
Pages : 83

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Author: Zongzhong Tian
Publisher:
ISBN:
Category : Electronic traffic controls
Languages : en
Pages : 106

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Author: Hasan Ozer
Publisher:
ISBN:
Category : Left-turn lanes
Languages : en
Pages : 91

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Author: Michael A. Perfater
Publisher:
ISBN:
Category : Automobile driving
Languages : en
Pages : 42

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More than 70% of motorists returning a questionnaire distributed for the study favored the exclusive/permissive signal, while about 17% said the signal reduced delays, and 30% said it created a hazard. Intersections with one or more right-turn-on-red movements seemed especially susceptible to vehicular conflicts. The ratios of accidents involving left-turning vehicles to all accidents at intersections appeared to increase after the E/P signals were installed.

Author: F. Adam King
Publisher:
ISBN:
Category : Traffic conflicts
Languages : en
Pages : 61

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Selection of the left-turn phasing mode is a significant decision for the safe and efficient movement of left-turning traffic at signalized intersections. Because of different safety and operational effects associated with the signal left-turn mode, the two must be evaluated concurrently and be balanced based on capacity and crash potential when protected-only, permissive-only, and protected-permissive left-turn (PPLT) phasing modes are compared. The choice between left-turn phasing modes can be made on a time-of-day basis so that changing traffic conditions are accommodated appropriately. The purpose of this study was to define guidance that field traffic engineers can use to select the appropriate left-turn mode based on prevailing traffic conditions by time of day. In particular, guidance on the use of PPLT or permissive-only with flashing yellow arrows (FYAs) to indicate permissive movements was of interest to the Virginia Department of Transportation (VDOT). Prior to the development of time-of-day guidance, the overall safety effects of converting between left-turn phase modes and indications (or displays) needed to be explored. The study examined the impact of converting from a circular “green ball” display for the permissive portion of PPLT phasing to the FYA signal indication and converting from protected-only phasing to PPLT with FYA. To quantify these conversions, a before-after evaluation of signal conversions was performed using standard Bayesian methods to develop crash modification factors from field data for 28 intersections in Virginia. For these intersections, the expected crash reduction after conversion from PPLT to PPLT-FYA was estimated as 12 percent (total crashes), 14 percent (fatal and injury crashes), and 30 percent (angle crashes), which was consistent with results from previous studies. In evaluating different left-turn phasing modes on a time-of-day basis, crash risk, left-turn conflicts, and capacity prediction models for permissive-only and PPLT modes were developed using simulation data. A total of 750 unique scenarios based on different combinations of intersection characteristics, traffic signal parameters, and traffic volumes were simulated in VISSIM, and trajectory files were processed using Surrogate Safety Assessment Model software to determine the number of conflicts per scenario. Based on the outputs of the simulation models, prediction models for determining left-turn capacities and the expected number of left-turn conflicts per hour per 100 left-turning vehicles were created using multiple linear regression. A final model predicting the average crash risk per hour based on the predicted number of conflicts was developed. The three models created were incorporated into a single spreadsheet tool that can be used by VDOT engineers in determining phasing mode on a time-of-day basis.

Author: Joseph E. Hummer
Publisher:
ISBN:
Category : Electronic traffic controls
Languages : en
Pages : 240

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Author:
Publisher:
ISBN:
Category : Traffic signs and signals
Languages : en
Pages : 124

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A determination of the differences between flashing yellow and circular green permissive signal indications displayed to motorists in a separate left turn lane with a separate indication.

Author: James L. Pline
Publisher: Transportation Research Board
ISBN:
Category : Controlled access highways
Languages : en
Pages : 100

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Book Description
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.

Author: National Research Council (U.S.). Transportation Research Board
Publisher:
ISBN:
Category :
Languages : en
Pages : 83

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