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SH 242ADAPTIVE TRAFFIC SIGNAL
SYSTEM DEPLOYMENT
TxDOT Houston
October 13, 2015
Steve Chiu – TxDOT
Manu Isaac – Kimley-Horn
The Corridor
SH 242
– North of Houston
– Near Woodlands
Six Signals west of IH 45 (St Luke’s to Gosling)
In a Rapidly Growing Area
Congested with Closely Spaced Signals
Unpredictable Traffic Patterns
–Serves a College, Schools, Churches, Shopping Centers, Hospitals, etc.
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Adaptive Traffic Control Systems (ATCS)
Automates Signal Monitoring and Timing Adjustments
Adjusts Timings in Real Time Based on Traffic
ATCS is Gradually Gaining Acceptance in US
Few Adaptive Systems Available
– SCOOTS, SCATS, RHODES, OPAC, InSync, ACS Lite, etc.
ACS Lite was used for SH 242
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Why ACS Lite?
Developed by FHWA
Focus on Reducing Installation and Operations Costs
Collaborative Effort initiated in 2002
– Siemens, University of Arizona, Purdue University, and few
Controller Manufacturers
Four Field Evaluations in 2007
– Included Houston, TX (others in OH, FL, CA)
Houston’s ACS Lite was Deactivated shortly
– TxDOT still retained License
In 2012 - TxDOT Houston Decides to Use it for SH 242
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ACS Lite Overview
Primarily for Closed Loop Arterial Signal Systems
Designed to Adapt the Splits and Offsets
Maximum of 32 signals in a System
Minimal Firmware Upgrades
Adaptive Computations Isolated to a Single Controller
Cycle Lengths based on Time of Day (TOD) schedules
Specified Optimization Steps (5-10 minutes)
Adjusts Splits and Offsets
by small amounts (2-5 seconds)
Significant Benefit with Minimum Agency Investment
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SH 242 Signals
1 Diamond and 6 Standard intersections
6 signals using ACS Lite – but not IH 45 Diamond
– St Luke’s, Maverick, Achievement, Honor Roll, Windsor Hills, Gosling
Majority have Split Side Street Phasing
Had Video Detection but not very Functional
Fiber Communication between Signals
NEMA cabinets with mainly Siemens Controllers
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Signal Equipment Requirements
Communications - IP or Serial
Vehicular Detection
– Can be any Detection Technology
– One Detector for each Phase
– Individual Lane-by-Lane Monitoring Preferable
– Stop Bar Detector (within 100 ft of Stop Bar)
– Advance Detection in “Dilemma Zone” (optional)
– Use Exit or Mid-block Detectors for Saturated Corridors
– Individual Detector Lead-In Cables and Cards
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Pre-Deployment Tasks
Field Investigation
Traffic Data Collection
– 24-hour ATR Counts
– Turning Movement Counts
– Travel Time Runs
Signal Timing Development
– Baseline to run ACS Lite System
Communications and Detection
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ACS Lite Implementation
ACS Lite Software
Adaptive Master
Signal Upgrades
– Controller Switch-outs
– Detector Installation
– Detector Cards
Comm. Setup
IP Addressing
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ACS Lite Programming
ACS Lite has a User Friendly GUI
Similar to Many Signal System Software
System Modules
Configuration
– Detector
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Programming – Date/Time/Schedule
Date/Time Module
Schedule/TOD Plans
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Programming – Ring/Phase
Ring Configuration
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Phase Data
Programming – Patterns
Patterns or Split Plans
Multiple Patterns for Each Split
Number of Patterns per Split is User Defined
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Programming – Adaptive Setup
ACS Lite Adaptive Settings
– Global Settings
– Controller-Specific
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Programming – Adaptive Setup
Global Settings
– Offset
– Split
– Adjustment Interval
Controller Specific
– Phase Biasing
– Peds, Transitions
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ACS Lite Operation
Check all setups are validated
Turn System to Control Mode
Watch it Run
System Monitoring
–Phase
–Offset
–Detector
–Historical Data
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ACS Lite Status Monitoring
Phase Utilization
– Saturation Rates
– Average Green
– Unused Green
Detector Status
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ACS Lite Status Monitoring
Flow Profile
– Offset Adjustment for Progression
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ACS Lite Split Adjustment
Splits Adjusted Based on Utilization
– Split Status is Color Coded
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Summary
Travel Time and Delay Savings
– Travel times: ~10%; Delays: ~25%
Post-Deployment Intangibles
– Less Congestion
– Fewer Complaint Calls
–Minimized Queues
Next Steps
– Add Adjacent Signals including Diamond
– Other Controllers and Corridors
20
Thank you
Manu Isaac, P.E. Steve Chiu, EIT
Kimley-Horn and Associates Texas Department of Transportation
Houston, Texas Houston District
281-920-6306 713-802-5936
Manu.Isaac@kimley-horn.com Steve.Chiu@txdot.gov
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