Transcript LADOT''S ADAPTIVE TRAFFIC CONTROL SYSTEM (ATCS)

LADOT’S ADAPTIVE
TRAFFIC CONTROL SYSTEM
(ATCS)
Presentation at the TRB Workshop on Adaptive
Traffic Signal Control Systems, Sponsored by
Signal Systems Committee
January 9, 2000
GENERAL DESCRIPTION
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PC-based real-time adaptive traffic control system
Developed by LADOT staff
Funding provided by City of Los Angeles, LACMTA
and FHWA
Window NT with real-time extension
Distributed client-server architecture
Up to 400 intersections and 6400 detectors per
system
Currently 237 intersections on-line
Plan to cover 2500 intersections in 3 years
WORKSTATION DISPLAY
BASIC PHILOSOPHY
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Develop an open system to test various control
algorithms
 Adjust signal timing on a cycle-by-cycle basis:
– Cycle Length
– Splits (Critical Intersection Control)
– Offset (Critical Link Control)
 Each Optimizer can function independently
 Maximum flexibility in section assignment
 Avoid overreacting to short-term variations
 Capable of responding to spikes in traffic demand
CYCLE LENGTH DISPLAY
CONTROL PARAMETERS
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Volume and Occupancy, collected every
second, but used every cycle
Speed
Detector location
Queue length
Upper and lower limits of cycle length
Phase sequence is fixed
Minimum phase green time
DETECTOR DATA
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At least one detector per phase
Detectors located 200’-300’ upstream of
the intersection
Identify and screen out bad detectors
Smooth calculated demands
Project new cycle lengths
Prorate phase splits based on fixed timing
plan when detector data is not available
OVERSATURATED CONDITIONS
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For isolated intersections
– Adapt to high occupancy data with longer
cycle length
– Adjust splits based on phase demands
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For major arterials
– Identify critical link(s) and provide progression
for the congested approach(s)
– Permit double cycling at minor intersections
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For networks
– Need further research and development
TRANSIT PRIORITY
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Use loop-transponder technology to
detect buses
Check bus schedule in the central
database
Provide green extension/red truncation for
late buses when needed
Calculate bus arrival time and determine
the extension time
Minimize adverse impact on cross streets
traffic
TRANSIT PRIORITY
SYSTEM ARCHITECTURE
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Centralized area computers (PC Server)
communicate to local controllers.
 Multi-port serial cards connect to
communication lines.
 GUI Client running on area computers and
workstations.
 Main Data Server provides central traffic
data base and coordinates area
computers.
COMMUNICATION SYSTEM
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Dedicated communication path between
host and local controllers
Time division multiplexing
Local controllers polled once per second
at 1200 bps
Four intersections per communication
line.
Multiple communication protocols
Download/Upload to local controllers
LOCAL CONTROLLERS
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Type 170 controller.
– BI Tran Systems 172.3 software.
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Type 2070 controller.
– City of L.A. Traffic Signal Control
Software.
CENTRAL HARDWARE REQUIREMENTS
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Rack mounted server with a backup PC.
– 350 MHz PC with 192 MB RAM
 Workstation with two 21-inch monitors.
 Multi-port PCI serial cards.
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Ethernet network.
INSTALLATION COST
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Central computer hardware - $40,000 to
$50,000 per system
Central software - $1,000 & LADOT license
Local controllers - $8,000-$10,000 per
intersection
Loop detectors - $5,000-10,000 per
intersection
Communications system - vary by types
OPERATIONS AND MAINTENANCE
Central hardware - minimal.
 Central software - update costs.
 Communications network - labor
costs for repair.
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CONTACT PERSONS
Verej Janoyan, LADOT
(213) 580-5359
e-mail:[email protected]
Kang Hu, LADOT
(213) 485-8523
e-mail:[email protected]