Transcript The RHODES Prototype: A Technical Review

RHODES
RHODES:
Fundamental Principles
Larry Head, Gardner Systems
Pitu Mirchandani, University of Arizona
TRB Annual Meeting 2000
Workshop on Adaptive Signal Control Systems
Gardner Systems
RHODES
Overview
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Basic Philosophy of RHODES
Control Variables
Data Sampling, Filtering and Smoothing
Phasing Flexibility
Measures of Effectiveness
Oversaturated Conditions
Preemption/Priority
Gardner Systems
RHODES
Basic Philosophy of RHODES
• to proactively respond to and utilize the
natural stochastic variations in traffic
flow with the appropriate time scale
• to operate within the framework of North
American traffic signal controllers
Gardner Systems
RHODES
System Architecture - Hierarchical
Scenario
Historical/Infrastructure Data
Origins/Destinations
Destinations/Origins
Network Load
Control
Current Capacities, Travel Times,
Network Disruptions
Network Load
Estimator/Predictor
(minutes/hours/days)
Network
Loads
Network Flow
Control
Target
Timings
Platoon Flow Prediction
(minutes)
Network Flow
Estimator/Predictor
Actual
Timings
Intersection
Control
Vehicle Flow Prediction
(seconds)
Intersection Flow
Estimator/Predictor
Control
Signal
Traffic Signal
Activation
Actual Travel
Behavior and Traffic
Gardner Systems
ATIS
Detectors and
Surveillance
y(t)
Measurements
RHODES
Control Variables
(interpreted to mean: Model and User Supplied Parameters)
• Structural (static)
– Geometric Description of Network
– Location/Type of Detectors
• Traffic Dynamics Parameters (adaptive)
– Saturation Flow, Turning Proportions…
• Signal Control (scheduled)
– Phasing, Minimum, Maximum, Pedestrian,….
• Optimization Parameters
Gardner Systems
RHODES
Control Variables
• Structural
– Geometric Description
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Link-node representation
Lanes, turning pockets, etc.
Lane Channelization
Lane Utilization
Gardner Systems
RHODES
Control Variables
• Structural
– Detectors
• Location (e.g. 224’ upstream - Passage)
• Type
– Passage (counting)
– Presence (stop bar)
– Detector Movement Assignment
– Prediction Feed Assignment
Gardner Systems
RHODES
Control Variables
• Traffic Dynamics Parameters
– Turning Percentage
• Dynamic using OD Estimation (currently static)
– Queue Discharge Rates - by movement/phase
• Saturation Flow Rate
• Dynamic using Queue Estimate and Presence
Detectors
• Start-up Lost Time
– Link Free Flow Speed
• Free Flow Corrected for Volume/Occupancy
Gardner Systems
RHODES
Control Variables
• Signal Control Parameters
– Phase (optimization stage)
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Allowable movements
Skipping
Minimum Green
Maximum Green (optional)
Amber & Red Clearance Times
Gardner Systems
RHODES
Control Variables
• Optimization Parameters
– Target Phase Evaluation Order
• ABCDACDE...
– Horizon
• User-definable, now using 45 seconds
– Resolution
• 1 second, 2 second, etc…….
Gardner Systems
RHODES
Data Sampling, Filtering and
Smoothing (data characteristics)
• Data Sampling
– data resolution = 1/second
– detector signals
• passage (count of falling edges)
• presence (state of detector just before end of second)
– Signal state (phase, interval)
• Filtering = NONE
• Smoothing = NONE
Gardner Systems
RHODES
Phasing Flexibility
• Number of Phases
– Any number of stages
D E
A B
C
• Flexibility in Phase Order
B
– for any optimization - select desired phase order
A
B
D
Gardner Systems
B
E
C
RHODES
Phasing Flexibility
• Currently assumes a fixed phase order
– rolling horizon =ABCDEA, BCDEAB,…..
• Phase Skipping allowed
– user selectable
– decisions = {0, min, min+1, ….., max*}
• for each phase
*optional
Gardner Systems
RHODES
Measures of Effectiveness
• Internal to RHODES
– Queue Size (number of vehicles) Estimate
– Predicted Link Flow Profiles
– Predicted Delay
• based on current queue and predicted arrivals
• External
– Queue Size
– Predicted Arrival Profile
Gardner Systems
Special Features for
Oversaturated Conditions
RHODES
• Consideration for Queue Spillback
– adjust departure rate for movements with
upstream queue spillback
– delay “discounting” for movements where
excessive downstream delay will occur
Gardner Systems
RHODES
Transit Priority
• Used coordination method
– Progression band
• Priority Band for Detected Buses
– Near upstream detection
– Far side stations
– Conditional on headway lateness
Gardner Systems
RHODES
Fire Priority
• Not in current RHODES model
• Potential route priority
– Using coordination method (bandwidth)
• Preemption provided by underlying
controller logic
– Ignore the adaptive control commands when a
preemption event is timing
Gardner Systems
RHODES
Arterial/Network
• Designed for both
• Most experience/experimentation on
arterials
• Optimization horizon (approx. 45 secs.)
– need to populate predictions
– travel time between intersections defines the
horizon over which optimization has data
Gardner Systems
RHODES
END SESSION 1
Gardner Systems
RHODES
RHODES:
Equipment Requirements
Larry Head, Gardner Systems
Gary Duncan, Econolite Control
Products
Gardner Systems
RHODES
Overview
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System Architecture
Data requirements
Communication requirements
Local Controllers
Central Hardware requirements
Installation cost ranges
Operations & Maintenance cost ranges
Gardner Systems
RHODES
Architecture
• RHODES
–Hierarchical
• Network Loading
• Network Flow Control
• Management System
–Distributed
• Local Intersection Control
Gardner Systems
RHODES
System Architecture
Workstation
LAN
Workstation
ATMS
Servers
Field Communications
Gardner Systems
RHODES
Architecture
• Traffic Adaptive Signal Control is an added
capability of an ATMS
• RHODES has been designed to operate as
an extension of existing ATMS systems
• Requirements are for
– Additional Communications
– Additional Detection
– Additional Processing
Gardner Systems
RHODES
Architecture
Workstation
Workstation
LAN
ATMS
Servers
*Additional Detection
*Additional Communications
Field Communications
*Additional
Processor
Gardner Systems
RHODES
Data Requirements
(Number, Type and Location of Sensors)
• Observability
– need to be able to observe vehicle flows and
flow dynamics
• Predictability
– need to be able to predict vehicle flows over a
prediction horizon of interest
• Flexibility
– need to accommodate wide range of detector
locations
Gardner Systems
RHODES
Data Requirements
(Number, Type and Location of Sensors)
dA
dA
B
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dA
dA
B
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(iii)
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Gardner Systems
(ii)
t
(iv)
t
RHODES
Data Requirements
(Number, Type and Location of Sensors)
Prediction Generators
Prediction Generators
Prediction
Receiver
Prediction Generators
Gardner Systems
RHODES
Data Requirements
(Number, Type and Location of Sensors)
• Detectors
– Passage (upstream)
• Count of number of passed vehicles (trailing edge)
• Used for flow prediction and queue estimation
– Presence (stop bar)
• State of detector at end of second
• Used for queue estimation
– IF(presence = 0) queue =0
Gardner Systems
RHODES
Communications Requirements
(Architecture, Polling Time, Bandwidth)
• Architecture
– Peer-to-Peer Communications
– Central-Intersection Communications
• Polling Time (options)
– Discrete Event
– 1 message/second
• Bandwidth
– depends on architecture
Gardner Systems
RHODES
Communications Requirements
(Architecture, Polling Time, Bandwidth)
• Architecture - Alternatives
– Token Ring
– Ethernet
– Point-to-Point, Tree
• Technology
– Field Hardened
– $$$
Gardner Systems
RHODES
Peer-to-Peer Communications:
Tucson and Seattle
Central Management System
Optelecom 9712 Modem Pairs:
3 - 9600 Baud RS 232
1 - 19.2K Serial/PTZ
1 - Full Motion Video
1 - 1200 Baud Voice
Communications Hub
Figerlign Mux:
1 - T1 Data (6 - RS-232)
9 - Full Motion Video
All Communications are over single mode fiber.
The link between the communications hub and the central
management system in Seattle is TBD.
Figure 1: Peer-to-Peer Communications Architecture for Tucson and Seattle.
Gardner Systems
Intersection Controllers
(2070 with MEN CPU)
RHODES
Communications Requirements
(Architecture, Polling Time, Bandwidth)
• Bandwidth (approx.)
– central
• hub-central (8 intersections)
• total
= 150 bytes/sec
= 1200 *10 (bits/byte)
= 12,000 bps
– peer-to-peer packet:
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overhead (header, trailer, etc)
data (predictions, signal)
packet (estimated total)
4 packets/sec
central
total
10 bytes
+ 30 bytes
= 40 bytes
= 160 bytes/sec
+ 150 bytes/sec
= 310 *10 = 3100
– Recommend 19.2Kbps for Central,
– 9600 bps for peer-to-peer
Gardner Systems
RHODES
Hardware Requirements
(Central, Intermediate Field, Local Processor)
• Central
– PC-based traffic server (e.g. icons )
– Serial Communications (e.g. Rocket Port)
TM
• Intermediate Field
– Field Hardened PC *+ Serial Comm
• Local Processor (options)
– 2070 with VME Co-processor
– standard controller+Co-processor
Gardner Systems
RHODES
Installation Cost Ranges
• Difficult to estimate
– Project dependent
– Architecture dependent
• Several projects estimated in the range of
$45,000 - $50,000 per intersection including
hardware + engineering
• License: The University of Arizona (approx.
$500/intersection)
Gardner Systems
RHODES
O&M Cost Ranges
• Incremental cost based on additional
hardware (including detection) and software
• Cost savings based on improved signal
timing
Gardner Systems