05/16/2008 Improved Traffic Signal Efficiency in Rural Areas through the use of Variable Maximum Green Time Aswini Rajagopalan

05/16/ Outline Introduction Definitions Work Done By Others Research Plan Site Selection and Description Methodology Results and Discussion Conclusions and Recommendations

05/16/ Introduction: Traffic Signal? Why do we need it? Where do we install it?

05/16/ Introduction (contd): Working of a traffic signal:  Timers What is being timed in a traffic signal?  Green  Yellow  Red

05/16/ Introduction

05/16/ Introduction Contd… Statistics Researchers at Oak Ridge National Laboratory  296 million vehicle hours of delay  56% - poor traffic signal timings. Updated Traffic Signal Timings  10 to 40% reduction in delay,  10% reduction in fuel consumption,  22% reduction in harmful emissions

05/16/ Introduction Contd… Modes of Traffic Signal Operation:  Pre-timed mode Cycle lengths, phases, green times are all preset  Actuated mode Green Time could be modified according to the demand. Phase can be terminated in the absence of demand.

05/16/ What is the problem? “UNMET DEMAND”

05/16/ Definitions Minimum Green Time Vehicle Extension Normal Maximum Green Time Dynamic Maximum Green Time/Variable Maximum Green Time Dynamic Maximum Step Size

05/16/ VMGT Variable Maximum Green Time  variation of maximum green time in a step-wise manner  according to the traffic fluctuations (unmet demand),  within certain specified limits of green  in an actuated phase. It is an additional feature of modern traffic controllers.

05/16/ Terminology (Operation of VMGT) Gap Out Max Out

05/16/ Variable Maximum Green Time Picture taken from RESEARCH REPORT ON IMPROVING DIAMOND INTERCHANGE OPERATIONS USING ADVANCED CONTROLLER FEATURES By Engelbrecht et al(2001)

05/16/ My Study Objectives:  Evaluate a generic set of VMGT parameters that can be used to reduce the delay and increase the throughput of an isolated intersection. Methodology:  Software-in-the-Loop Simulation  Traffic simulation software - VISSIM

05/16/ Work Done by Others Engel Brecht et al(2001)  Improving diamond interchange operations using Advanced Controller Features.  one among the eight features considered.  Adaptation to unexpected demand- positive results.

05/16/ Work Done by Others Contd… Yun et al (2007)  evaluated the Adaptive Maximum feature in the EPAC300 actuated Traffic Controller.  Hardware-in-the-loop Simulation.  compared the VMGT with both a normally optimized maximum green and an arbitrarily large maximum green.  Result- VMGT performed better.

05/16/ Gaps in the Literature Generic set of VMGT parameters  Yun- VMGT parameters based on site- specific optimized timing. All phases  EngelBrecht - exit ramp phases on a diamond interchange. 16-hour volumes  Yun- peak hour volumes

05/16/ Research Plan Data Collection Base Model Development Development of Timing Plans Simulation Data Reduction and Initial Strategy Development Multi Run Simulation and evaluation of results Conclusions and Recommendations

05/16/ Site Selection Site selection criteria:  Isolated intersection  At a Rural area.  Presence of apparent queuing.  Difference in volume.

05/16/ Site description (Site 1) Site 1 – NC 11 at NC 5, Pinehurst,NC Speed Limit –  East-west -55 mph  North-south- 35 mph ADT vehicles

05/16/ Site description (Site 2) Site 2 – Dixie at 9 th, Cookeville, TN Speed Limit- 15 mph ADT vehicles

05/16/ Site description (Site 3) Site 3 – Willow at Jackson, Cookeville,TN Speed Limits  East-West – 30 mph  North- South- 35 mph ADT – 40,000 vehicles

05/16/ Methodology

05/16/ Different Timing Plans TreatmentGreen times DefaultMaximum = 20 seconds OptimizedOptimal green times for AM, Mid day and PM were used. VMGTNormal Maximum = 20 seconds Dynamic Maximum = 60 seconds Dynamic step size = 10 seconds Existing (for only Site 3)Used the maximum green times that were currently used in the field

05/16/ Different Timing Plans Contd… Default Timing Plan Optimized Timing Plan

05/16/ Different Timing Plans Contd… VMGT Timing Plan

05/16/ Results and Discussion Three performance measures:  Throughput Analysis  Delay Analysis  Signal Analysis

05/16/ Throughput Analysis – Site 1 Throughput Analysis:  Can a signal using VMGT serve the same amount traffic as a signal using optimized timings?

05/16/ Throughput Analysis – Site 2

05/16/ Throughput Analysis – Site 3

05/16/ Delay Analysis – Site 1 Can VMGT perform better than or equivalent to optimized treatment in terms of delay?

05/16/ Worst Approach and Worst Movement Delay – Site 1

05/16/ Delay Analysis – Site 2

05/16/ Worst Approach and Worst Movement Delay – Site 2

05/16/ Delay Analysis- Site 3

05/16/ Worst Approach and Worst Movement Delay – Site 3

05/16/ Signal Analysis Whether VMGT was able to increase or decrease the green time according to the varying demand in a reasonable way? In other words whether VMGT is able to provide reasonable cycle length?  Concern

05/16/ Signal Analysis

05/16/ Conclusions Contd… Signal Analysis  Whether VMGT was able to increase or decrease the green time according to the varying demand in a reasonable way? – YES  In other words whether VMGT is able to provide reasonable cycle length? -YES

05/16/ Cycle Length- Site 1

05/16/ Signal Analysis- Site 3

05/16/ Conclusions Throughput Analysis:  Can a signal using VMGT serve the same amount traffic as a signal using optimized timings? – YES Delay Analysis:  Can VMGT perform better than or equivalent to optimized treatment in terms of delay? – YES Site 1 - sharp AM peak Site 3 - Existing↔VMGT Sites 1and 2,VMGT = Optimized Site 3, VMGT = best Intersection Worst approach/ movement

05/16/ Recommendations Generic VMGT parameters  Normal Maximum Green Time = 20 seconds  Dynamic Maximum Step Size = 10 seconds  Dynamic Maximum Green Time = 60 seconds Controller settings: 2 (max outs and gap outs) Detection is compulsory.

05/16/ Future Research  Proper methodology oDynamic Maximum Green oDynamic Step Size  Coordinated Actuated control.  Different Strategies with different Dynamic step sizes and Dynamic maximum could be tried. oFor e.g. – from 10 to 15 secs for step for site 1.

05/16/ Acknowledgements Advisor – Dr. Steven Click, Tennessee Technological University. Vice President, CTE, Nashville – Jim Morinec PTV America - Kiel Ova Kim King, Marshall Boyd – CTE, Nashville

05/16/2008 Questions?