Smart Information for a Sustainable World
True Adaptive Signal Control A Comparison of Alternatives
Technical Paper #1154
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Presentation to the 18th World Congress on
Intelligent Transport Systems
Technical Session 95 (TS95)
Wednesday 19 October 2011
19 Oct. 2011
Authors
Cary Vick, PE – Telvent Transportation (presenting)
Farhad Pooran, PE, PhD - Telvent Transportation
José Carlos Riveira Martinez - Telvent Trafico y Transporte
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Purpose / Agenda
Clarify definitions and capabilities of true adaptive signal control
Urge selection of some type of advanced signal controlWe can do better with what we have
It’s not just for research any moreIt’s not just for research any more
Summarize approach of available technologies / products
Not a comprehensive review and comparison of results
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Deployment of Adaptive Signal
Control Technologies
SCATS
SCOOT
ACSLite
InSync
RHODES
OPAC
LA ATCS
State with Active ASCT
State with Pending ASCT
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Categories of Signal Control
Definitions (USDOT / FHWA Traffic Signal Control Handbook (Gordon and Tighe)):
Isolated
Time Based CoordinationTime Based Coordination
Interconnected Control
Traffic Adjusted Control
Traffic Responsive Control
Traffic Adaptive Control
The primary differentiator for Traffic Adaptive Control is the use of
a traffic flow model to predict demand and adapt timings to meet
expected traffic flows5
What is NOT Adaptive Control
Traffic Responsive: Trigger plan or timing changes
Volume Density: Modify parameters based on demandModify parameters based on demand
Off-line Optimization: Real time measurements trigger re-optimization of timing plans
Central + Local Optimization:Real time measurements trigger re-optimization of selected timing parameters (off set) then local
control applies and adjusts
All approaches have value, but they are NOT
adaptive signal control6
Summary of ASCT AlternativesFunction
Control System
ACS Lite InSync LA ATCS OPAC RHODE
S
SCATS SCOOT UTOPIA ITACA NAZTEC QuicNet
Action P + R P + R P + R P + R P
(only)
R
(only)
P + R Pro-active P + R R
(only)
R
(only)
Architecture Dist. Dist. Central Dist. Central Central Central Central Central Central Central
Simulation
Model?
Yes Yes Yes Yes Yes No Yes Yes Yes No No
Time Frame 5–10 min Phase/
Cycle /
15 min.
Cycle Phase/
Cycle /
5 min.
Sec by
sec
Cycle Cycle/
5 min.
3 sec &
Cycle
5 sec &
Cycle
5–10 min 5–10 min
Optimization S / O S / C / O
/ PS
S / C / O S / C /
O
S S / C /
O
S / C / O
/ PS
S / PS S / C / O
/ PS
S / C / O S / C / O
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Adaptive Traffic Signal Control Processes
Offset Optimizer Split Optimizer Cycle Optimizer
Offset Split Cycle
Traffic Engineer
Expert Rules
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Offset
weights
Split
weights
Cycle
weights
Intersection control
Platoon modeling
VolumeOccupancy
B
A
A + BA or B
Control Center
Traffic Flow / Queue Model
�Operator /
Traffic Engineer Traffic data at detection ponts
Intersection structure
Operations of Adaptive Signal Control
�
Street Observer for Calibration
Mean travel time
Queue lengths
Exit flows
Queue capacity
Real Time Data
Pro Active
Timing Changes
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Weighting Factors Apply Expert Rules to
Adaptive Control Strategies
•ITACA Expert Rules System
•Usable range is -10 to +10
• Positive weights apply importance to affected links
• Negative weights reduce importance of associated links
• 2 weighting parameters for each link (split and offset)
• 1 weighting parameter for each intersection (cycle)
• Can be adjusted in real time manually or by expert rules• Can be adjusted in real time manually or by expert rules
• Each final weight may reflect adjustments by different sources
If Then UntilRoute A is highly
congested
Reduce weight for
Transversal Route B
Intersection B20
has maximum queue
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CabinetCabinetCabinetCabinet
OPAC Hardware ConfigurationAdvanced Traffic Controllers Advanced Traffic Controllers Advanced Traffic Controllers Advanced Traffic Controllers
OPAC Single Board Computer (local)OPAC Single Board Computer (local)OPAC Single Board Computer (local)OPAC Single Board Computer (local)
Upstream Advance DetectorsUpstream Advance DetectorsUpstream Advance DetectorsUpstream Advance Detectors
Traffic Signal Controller:Traffic Signal Controller:Traffic Signal Controller:Traffic Signal Controller:
Type 2070 or NEMA (TS1 / TS2)Type 2070 or NEMA (TS1 / TS2)Type 2070 or NEMA (TS1 / TS2)Type 2070 or NEMA (TS1 / TS2)
Stop Bar
Single Board Computer (Linux OS) running OPAC Single Board Computer (Linux OS) running OPAC Single Board Computer (Linux OS) running OPAC Single Board Computer (Linux OS) running OPAC
softwaresoftwaresoftwaresoftware
Force offs &
Holds
Detector Data
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ACS-Lite ArchitectureACSACSACSACS----Lite ComputerLite ComputerLite ComputerLite Computer
Minimum 9600 baud
Communications
(serial or IP)
On-street Master
(optional)
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Communications Interface
and/or
NTCIP Translators
NTCIP controllers or
Proprietary protocol controllers
(serial or IP)
NTCIP
Advantages of Predictive
Modeling
Continuous adjustment to changing demand
Pro-active timing changes
Optimal use of available capacityOptimal use of available capacity
Adjusts to incident conditions
The primary differentiator for Traffic Adaptive Control is the use of
a traffic flow model to predict demand and adapt timings to meet
expected traffic flows
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Cycle Length Adaptability
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Incident Incident Incident Incident
OccursOccursOccursOccurs
References:Stevanovic, Aleksandar, “Adaptive Traffic Control Systems: Domestic
and Foreign State of Practice” NCHRP Synthesis 403, Transportation
Research Board, Washington, DC, 2010
Gordon, Robert L, and Tighe, Warren “Traffic Control Systems
Handbook.” Federal Highway Administration Report FHWA-HOP-06-006, Handbook.” Federal Highway Administration Report FHWA-HOP-06-006,
Washington, DC, 2005.
Gartner, N.H., F.J. Poorhan, and C.M. Andrews. “Implementations and
Field Testing of the OPAC Adaptive Control Strategy in RT-TRACS.”
TRB Paper No. 02-3667 - Presented at the 81st Annual Meeting of the
Transportation Research Board, Washington, DC, 2002.
Riveira Martínez, José Carlos. “The Road to ITACA”, internal white paper,
Telvent, 2000.
MacGowan, J., and I. J. Fullerton. 1979. Development and testing of
advanced control strategies in the urban traffic control system. Public
Roads 43, no. 2, 3, and 4.
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Smart Information for a Sustainable World
Smart Information for a Sustainable World
Thank You19 Oct. 2011