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