RHODES Gardner Systems RHODES: Fundamental Principles Larry Head, Gardner Systems Pitu Mirchandani,...
Transcript of RHODES Gardner Systems RHODES: Fundamental Principles Larry Head, Gardner Systems Pitu Mirchandani,...
RHODES
RHODES:Fundamental Principles
Larry Head, Gardner Systems
Pitu Mirchandani, University of Arizona
TRB Annual Meeting 2000Workshop on Adaptive Signal Control Systems
RHODES
Overview
• Basic Philosophy of RHODES• Control Variables• Data Sampling, Filtering and Smoothing• Phasing Flexibility• Measures of Effectiveness• Oversaturated Conditions• Preemption/Priority
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
RHODES
System Architecture - Hierarchical
Destinations/Origins
Network LoadControl
Network FlowControl
IntersectionControl
Traffic SignalActivation
Detectors and Surveillance
Actual Travel Behavior and Traffic
NetworkLoads
Target Timings
ActualTimings
ControlSignal
Vehicle Flow Prediction
Scenario
Origins/Destinations
Current Capacities, Travel Times,Network Disruptions
(seconds)
(minutes)
(minutes/hours/days)
Platoon Flow Prediction
Network LoadEstimator/Predictor
Network FlowEstimator/Predictor
Intersection FlowEstimator/Predictor
Measurements
y(t)
ATIS
Historical/Infrastructure Data
RHODES
Control Variables
• 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
(interpreted to mean: Model and User Supplied Parameters)
RHODES
Control Variables
• Structural– Geometric Description
• Link-node representation
• Lanes, turning pockets, etc.
• Lane Channelization
• Lane Utilization
RHODES
Control Variables
• Structural– Detectors
• Location (e.g. 224’ upstream - Passage)
• Type– Passage (counting)
– Presence (stop bar)
– Detector Movement Assignment– Prediction Feed Assignment
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
RHODES
Control Variables
• Signal Control Parameters– Phase (optimization stage)
• Allowable movements
• Skipping
• Minimum Green
• Maximum Green (optional)
• Amber & Red Clearance Times
RHODES
Control Variables
• Optimization Parameters– Target Phase Evaluation Order
• ABCDACDE...
– Horizon• User-definable, now using 45 seconds
– Resolution• 1 second, 2 second, etc…….
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
RHODES
Phasing Flexibility
• Number of Phases– Any number of stages
• Flexibility in Phase Order– for any optimization - select desired phase order
A B C D E B
A B D 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
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
RHODES
Special Features for Oversaturated Conditions
• Consideration for Queue Spillback– adjust departure rate for movements with
upstream queue spillback– delay “discounting” for movements where
excessive downstream delay will occur
RHODES
Transit Priority
• Used coordination method – Progression band
• Priority Band for Detected Buses– Near upstream detection– Far side stations– Conditional on headway lateness
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
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
RHODES
END SESSION 1
RHODES
RHODES:Equipment Requirements
Larry Head, Gardner Systems
Gary Duncan, Econolite Control Products
RHODES
Overview System Architecture Data requirements Communication requirements Local Controllers Central Hardware requirements Installation cost ranges Operations & Maintenance cost ranges
RHODES
Architecture
• RHODES–Hierarchical
• Network Loading
• Network Flow Control
• Management System
–Distributed• Local Intersection Control
RHODES
System Architecture
ATMS
Servers
Workstation
Workstation
Field Communications
LAN
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
RHODES
Architecture
ATMS
Servers
Workstation
Workstation
Field Communications
LAN
Additional Detection
Additional Communications
Additional Processor
**
*
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
RHODES
Data Requirements(Number, Type and Location of Sensors)
(i) (ii)
(iii)
(iv)
di
dA
di
dA
di
dA
di
dA
B B
B B
t t
t t
RHODES
Data Requirements(Number, Type and Location of Sensors)
Prediction Generators
Prediction Generators
Prediction Generators
PredictionReceiver
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
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
RHODES
Communications Requirements(Architecture, Polling Time, Bandwidth)
• Architecture - Alternatives– Token Ring– Ethernet– Point-to-Point, Tree
• Technology– Field Hardened– $$$
RHODES
Peer-to-Peer Communications: Tucson and Seattle
Central Management System
Communications Hub
Intersection Controllers(2070 with MEN CPU)
Optelecom 9712 Modem Pairs:3 - 9600 Baud RS 2321 - 19.2K Serial/PTZ1 - Full Motion Video1 - 1200 Baud Voice
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.
RHODES
Communications Requirements(Architecture, Polling Time, Bandwidth)
• Bandwidth (approx.)– central = 150 bytes/sec
• hub-central (8 intersections) = 1200 *10 (bits/byte)
• total = 12,000 bps– peer-to-peer packet:
• overhead (header, trailer, etc) 10 bytes• data (predictions, signal) + 30 bytes• packet (estimated total) = 40 bytes• 4 packets/sec = 160 bytes/sec• central + 150 bytes/sec• total = 310 *10 = 3100
– Recommend 19.2Kbps for Central, – 9600 bps for peer-to-peer
RHODES
Hardware Requirements(Central, Intermediate Field, Local Processor)
• Central– PC-based traffic server (e.g. iconsTM)– Serial Communications (e.g. Rocket Port)
• Intermediate Field– Field Hardened PC *+ Serial Comm
• Local Processor (options)– 2070 with VME Co-processor– standard controller+Co-processor
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)
RHODES
O&M Cost Ranges
• Incremental cost based on additional hardware (including detection) and software
• Cost savings based on improved signal timing