Evaluation of the Adaptive Maximum
Feature in the EPAC300 Actuated Traffic Controller Using Hardware-in-the-Loop
Simulation
By:
Byungkyu
“Brian” Park, Ph.D.
University of Virginia
Thornton Hall
351 McCormick Road
P.O. Box 400742
Charlottesville, VA 22904
Phone: 434-924-6347
Fax: 434-982-2951
E-mail: bpark@virginia.edu
Ilsoo
Yun, Ph.D.
University of Virginia
Thornton Hall
351 McCormick Road
P.O. Box 400742
Charlottesville, VA 22904
Phone: 434-825-9271
Fax: 434-982-2951
E-mail:
iy6m@virginia.edu
Matthew Best
University of Virginia
Thornton Hall
351 McCormick Road
P.O. Box 400742
Charlottesville, VA 22904
M.S., Civil Engineering, May 2007
Phone: 434-996-9118
Fax: 434-982-2951
E-mail: mgb3e@virginia.edu
A Research Project
Report for the Intelligent Transportation Systems Implementation Center (ITS)
A U.S. DOT University Transportation Center
Dr. Byungkyu “Brian” Park, Ph.D.
Department of Civil Engineering
Email: bpark@virginia.edu
Center for Transportation Studies at the University of Virginia produces outstanding transportation professionals, innovative research results and provides important public service. The Center for Transportation Studies is committed to academic excellence, multi-disciplinary research and to developing state-of-the-art facilities. Through a partnership with the Virginia Department of Transportation’s (VDOT) Research Council (VTRC), CTS faculty hold joint appointments, VTRC research scientists teach specialized courses, and graduate student work is supported through a Graduate Research Assistantship Program. CTS receives substantial financial support from two federal University Transportation Center Grants: the Mid-Atlantic Universities Transportation Center (MAUTC), and through the National ITS Implementation Research Center (ITS Center). Other related research activities of the faculty include funding through FHWA, NSF, US Department of Transportation, VDOT, other governmental agencies and private companies.
Disclaimer: The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. This document is disseminated under the sponsorship of the Department of Transportation, University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof.
|
1. Report No. |
2. Government Accession No. |
3. Recipient’s Catalog No. |
|||||
|
UVACTS-15-0-110 |
|
|
|||||
|
4. Title and Subtitle |
5. Report Date |
||||||
|
Evaluation of the Adaptive
Maximum Feature in the EPAC300 Actuated Traffic Controller Using
Hardware-in-the-Loop Simulation |
July 17, 2007 |
||||||
|
|
6. Performing Organization Code |
||||||
|
|
|
||||||
|
7. Author(s) |
8. Performing Organization Report No. |
||||||
|
Dr. Byungkyu “Brian” Park, Ph.D., Ilsoo Yun, Ph.D.,
Matthew Best |
|
||||||
|
9. Performing Organization and Address |
10. Work Unit No. (TRAIS) |
||||||
|
Center for Transportation Studies |
|
||||||
|
University of Virginia |
11. Contract or Grant No. |
||||||
|
PO Box 400742 Charlottesville, VA 22904-7472 |
|
||||||
|
12. Sponsoring Agencies' Name and Address |
13. Type of Report and Period Covered |
||||||
|
Office of University
Programs, Research Innovation and Technology Administration US Department of
Transportation 400 Seventh Street, SW Washington DC 20590-0001 |
|
Final Report |
|||||
|
|
|
14. Sponsoring Agency Code |
|||||
|
|
|
|
|||||
|
15.
Supplementary Notes |
|||||||
|
|
|||||||
|
16. Abstract |
|||||||
|
Several actuated traffic controllers contain the Adaptive Maximum
feature, with which the controllers can adjust the maximum green intervals
for actuated phases within specified upper and lower limits according to
fluctuating traffic demand. It has
been difficult, however, to evaluate the merits of this and other features
available in modern traffic controllers.
Recent developments in traffic signal control systems hardware and
software technologies have now made it possible to evaluate controller
features in a realistic and risk-free environment using hardware-in-the-loop
simulation (HILS). HILS is a method
of simulation in which one or more actual traffic signal controllers are
physically linked with a microscopic traffic simulator. This paper demonstrates the performance of the Adaptive Maximum
feature using HILS, which consisted of an EPAC300 traffic controller and the
VISSIM microscopic simulation model.
The demonstration was conducted at an isolated, fully actuated
intersection in Richmond, Virginia. In
a feasibility test of the Adaptive Maximum feature, the HILS results indicated
that the Adaptive Maximum feature was able to provide traffic signal control
operations as efficiently as normal maximum green intervals optimized by
SYNCHRO. However, in a robustness
test, where fifteen percent changes in traffic volumes were considered, the
Adaptive Maximum feature outperformed the normal maximum green
intervals. |
|||||||
|
17 Key Words Traffic Controller,
Hardware-in-the-Loop Simulation |
18. Distribution Statement |
||||||
|
|
No restrictions. This
document is available to the public. |
||||||
|
19. Security Classif.
(of this report) |
20. Security Classif. (of
this page) |
21. No. of Pages |
22. Price |
||||
|
Unclassified |
Unclassified |
22 |
N/A |
||||
Abstract
Several actuated traffic controllers contain the Adaptive Maximum feature, with which the controllers can adjust the maximum green intervals for actuated phases within specified upper and lower limits according to fluctuating traffic demand. It has been difficult, however, to evaluate the merits of this and other features available in modern traffic controllers. Recent developments in traffic signal control systems hardware and software technologies have now made it possible to evaluate controller features in a realistic and risk-free environment using hardware-in-the-loop simulation (HILS). HILS is a method of simulation in which one or more actual traffic signal controllers are physically linked with a microscopic traffic simulator.
This paper demonstrates the performance of the Adaptive Maximum feature using HILS, which consisted of an EPAC300 traffic controller and the VISSIM microscopic simulation model. The demonstration was conducted at an isolated, fully actuated intersection in Richmond, Virginia. In a feasibility test of the Adaptive Maximum feature, the HILS results indicated that the Adaptive Maximum feature was able to provide traffic signal control operations as efficiently as normal maximum green intervals optimized by SYNCHRO. However, in a robustness test, where fifteen percent changes in traffic volumes were considered, the Adaptive Maximum feature outperformed the normal maximum green intervals.
INTRODUCTION
As traffic congestion becomes more severe in its intensity and duration, traffic engineers have the challenging task of operating traffic signal systems more efficiently. To accomplish this, they have attempted to use green times more efficiently to reduce vehicle delays. For example, the implementation of isolated or coordinated-actuated traffic signal control systems over pre-timed signal control has improved the efficiency of green time allocation. In isolated, fully actuated signal control, detectors are placed on the approaches of an intersection to sense the presence of vehicles from the subject movements. They send these vehicle actuations to the controller, which then adjusts the subject phase length to serve current traffic demands. Under normal actuated operation without the volume-density control, three main settings govern the length adjustment of a phase—minimum green, maximum green, and vehicle extension. For example, if recall is not set for a phase and the phase receives no detector calls during its yellow and red intervals, it is skipped. An advantage of actuated traffic signal control over pre-timed traffic signal control is the ability to terminate the green time of the active phase immediately and to provide additional green time to the phases with demand. This function—gap out—is intended to serve approaches with demand if additional vehicles are not arriving on the current approach within the predetermined gap out time. Gap out provides flexibility in the allocation of green times when needed. Due to these merits, actuated traffic signal control is widely deployed across the U.S. (1).
Modern actuated traffic controllers have additional features that add to the overall efficiency of actuated traffic control. For example, the Adaptive Maximum feature (also known as Dynamic Maximum) is available in several actuated traffic controllers (2, 3, 4). Using this feature, controllers can adjust the maximum green intervals according to traffic fluctuations for actuated phases within specified upper or lower limits. This feature is especially useful at an isolated-actuated signal control.
It has been difficult in the past, however, to evaluate such a feature in the field or laboratory environment. Recent developments in hardware and software technologies in the transportation industry have introduced hardware-in-the-loop simulation (HILS), which allows for the evaluation of traffic controller features in a realistic and risk-free environment. In the engineering industry, HILS is a new method of simulation in which a physical device is added to simulation software to provide an effective platform for developing and testing real-time embedded systems (5). In the case of traffic simulation, a traffic signal controller is connected to a microscopic traffic simulation software program, such as CORSIM or VISSIM, in a personal computer. Here, the external controller operates the traffic signal in the microscopic simulation model instead of the software.
This paper aims to evaluate the Adaptive Maximum feature available in the EPAC300 actuated traffic controller using the VISSIM microscopic simulation model-based HILS. The feasibility of the Adaptive Maximum feature was first investigated. In this test, operations with the Adaptive Maximum settings were compared with the (1) normal maximum green settings optimized by Synchro (6), a macroscopic signal timing optimization model, and (2) excessively large maximum green settings. It is noted that the latter setting was tested to evaluate the performance of actuated control using only the gap out feature. For the feasibility test, observed traffic counts were used as the traffic demands in the VISSIM-based HILS; however, fifteen percent increases and decreases in traffic demands were assumed in the robustness test, which was intended to verify the proper operation of the Adaptive Maximum feature in different volume conditions.
LITERATURE REVIEW
Adaptive Maximum
As discussed, the Adaptive Maximum feature—or a similar one under a different name—is available in several different actuated traffic controllers. According to NTCIP 1202: Objective Definition for Actuated Traffic Signal Control Units (7), the Adaptive Maximum (referred to as Dynamic Maximum in NTCIP 1202) operation can be defined as a cycle by cycle maximum green interval adjustment within an upper and lower limit. The advantage of this feature is that the controller can adjust maximum green intervals according to the degree of traffic demand and fluctuations.
In the EPAC300 traffic controller, shown in Figure 1, the Adaptive Maximum operation has three main parameters: Maximum Green (seconds), Dynamic Maximum (seconds), and Dynamic Step (tenths of seconds). Here, Maximum Green is different from a normal maximum green time setting and works as the lower or upper limit in the operation. For example, after a phase maxes out on two consecutive cycles, and after each successive max out thereafter, the Dynamic Step value is added to the current normal maximum green time until before it is greater than the larger of Maximum Green or Dynamic Maximum. In a similar way, after a phase gaps out on two consecutive cycles, and after each successive gap out thereafter, the Dynamic Step value is subtracted from the current maximum green until before it is less than the smaller of Maximum Green or Dynamic Maximum. If a phase gaps out in one c