1. 05/16/2008 Improved Traffic Signal Efficiency in Rural Areas through the use of Variable Maximum Green Time Aswini Rajagopalan

2. 05/16/2008 2 Outline Introduction Definitions Work Done By Others Research Plan Site Selection and Description Methodology Results and Discussion Conclusions and Recommendations

3. 05/16/2008 3 Introduction: Traffic Signal? Why do we need it? Where do we install it?

4. 05/16/2008 4 Introduction (contd): Working of a traffic signal:  Timers What is being timed in a traffic signal?  Green  Yellow  Red

5. 05/16/2008 5 Introduction

6. 05/16/2008 6 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

7. 05/16/2008 7 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.

8. 05/16/2008 8 What is the problem? “UNMET DEMAND”

9. 05/16/2008 9 Definitions Minimum Green Time Vehicle Extension Normal Maximum Green Time Dynamic Maximum Green Time/Variable Maximum Green Time Dynamic Maximum Step Size

10. 05/16/2008 10 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.

11. 05/16/2008 11 Terminology (Operation of VMGT) Gap Out Max Out

12. 05/16/2008 12 Variable Maximum Green Time Picture taken from RESEARCH REPORT ON IMPROVING DIAMOND INTERCHANGE OPERATIONS USING ADVANCED CONTROLLER FEATURES By Engelbrecht et al(2001)

13. 05/16/2008 13 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

14. 05/16/2008 14 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.

15. 05/16/2008 15 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.

16. 05/16/2008 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

17. 05/16/2008 17 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

18. 05/16/2008 18 Site Selection Site selection criteria:  Isolated intersection  At a Rural area.  Presence of apparent queuing.  Difference in volume.

19. 05/16/2008 19 Site description (Site 1) Site 1 – NC 11 at NC 5, Pinehurst,NC Speed Limit –  East-west -55 mph  North-south- 35 mph ADT- 20000 vehicles

20. 05/16/2008 20 Site description (Site 2) Site 2 – Dixie at 9 th, Cookeville, TN Speed Limit- 15 mph ADT- 20000 vehicles

21. 05/16/2008 21 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

22. 05/16/2008 22 Methodology

23. 05/16/2008 23 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

24. 05/16/2008 24 Different Timing Plans Contd… Default Timing Plan Optimized Timing Plan

25. 05/16/2008 25 Different Timing Plans Contd… VMGT Timing Plan

26. 05/16/2008 26 Results and Discussion Three performance measures:  Throughput Analysis  Delay Analysis  Signal Analysis

27. 05/16/2008 27 Throughput Analysis – Site 1 Throughput Analysis:  Can a signal using VMGT serve the same amount traffic as a signal using optimized timings?

28. 05/16/2008 28 Throughput Analysis – Site 2

29. 05/16/2008 29 Throughput Analysis – Site 3

30. 05/16/2008 30 Delay Analysis – Site 1 Can VMGT perform better than or equivalent to optimized treatment in terms of delay?

31. 05/16/2008 31 Worst Approach and Worst Movement Delay – Site 1

32. 05/16/2008 32 Delay Analysis – Site 2

33. 05/16/2008 33 Worst Approach and Worst Movement Delay – Site 2

34. 05/16/2008 34 Delay Analysis- Site 3

35. 05/16/2008 35 Worst Approach and Worst Movement Delay – Site 3

36. 05/16/2008 36 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

37. 05/16/2008 37 Signal Analysis

38. 05/16/2008 38 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

39. 05/16/2008 39 Cycle Length- Site 1

40. 05/16/2008 40 Signal Analysis- Site 3

41. 05/16/2008 41 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

42. 05/16/2008 42 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.

43. 05/16/2008 43 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.

44. 05/16/2008 44 Acknowledgements Advisor – Dr. Steven Click, Tennessee Technological University. Vice President, CTE, Nashville – Jim Morinec PTV America - Kiel Ova Kim King, Marshall Boyd – CTE, Nashville

45. 05/16/2008 Questions?