RHODES Gardner Systems RHODES: Fundamental Principles Larry Head, Gardner Systems Pitu Mirchandani, University of Arizona TRB Annual Meeting 2000 Workshop on Adaptive Signal Control Systems

RHODES Gardner Systems Overview Basic Philosophy of RHODES Control Variables Data Sampling, Filtering and Smoothing Phasing Flexibility Measures of Effectiveness Oversaturated Conditions Preemption/Priority

RHODES Gardner Systems 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 Gardner Systems System Architecture - Hierarchical Destinations/Origins Network Load Control Network Flow Control Intersection Control Traffic Signal Activation Detectors and Surveillance Actual Travel Behavior and Traffic Network Loads Target Timings Actual Timings Control Signal Vehicle Flow Prediction Scenario Origins/Destinations Current Capacities, Travel Times, Network Disruptions (seconds) (minutes) (minutes/hours/days) Platoon Flow Prediction Network Load Estimator/Predictor Network Flow Estimator/Predictor Intersection Flow Estimator/Predictor Measurements y(t) ATIS Historical/Infrastructure Data

RHODES Gardner Systems 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 Gardner Systems Control Variables Structural –Geometric Description Link-node representation Lanes, turning pockets, etc. Lane Channelization Lane Utilization

RHODES Gardner Systems Control Variables Structural –Detectors Location (e.g. 224’ upstream - Passage) Type –Passage (counting) –Presence (stop bar) –Detector Movement Assignment –Prediction Feed Assignment

RHODES Gardner Systems 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 Gardner Systems Control Variables Signal Control Parameters –Phase (optimization stage) Allowable movements Skipping Minimum Green Maximum Green (optional) Amber & Red Clearance Times

RHODES Gardner Systems Control Variables Optimization Parameters –Target Phase Evaluation Order ABCDACDE... –Horizon User-definable, now using 45 seconds –Resolution 1 second, 2 second, etc…….

RHODES Gardner Systems 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 Gardner Systems Phasing Flexibility Number of Phases –Any number of stages Flexibility in Phase Order –for any optimization - select desired phase order ABC DEB ABD B EC

RHODES Gardner Systems 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 Gardner Systems 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 Gardner Systems 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 Gardner Systems Transit Priority Used coordination method –Progression band Priority Band for Detected Buses –Near upstream detection –Far side stations –Conditional on headway lateness

RHODES Gardner Systems 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 Gardner Systems 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 Gardner Systems END SESSION 1

RHODES Gardner Systems RHODES: Equipment Requirements Larry Head, Gardner Systems Gary Duncan, Econolite Control Products

RHODES Gardner Systems Overview  System Architecture  Data requirements  Communication requirements  Local Controllers  Central Hardware requirements  Installation cost ranges  Operations & Maintenance cost ranges

RHODES Gardner Systems Architecture RHODES –H ierarchical Network Loading Network Flow Control Management System –D istributed Local Intersection Control

RHODES Gardner Systems System Architecture ATMS Servers Workstation Field Communications LAN

RHODES Gardner Systems 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 Gardner Systems Architecture ATMS Servers Workstation Field Communications LAN Additional Detection Additional Communications Additional Processor * * *

RHODES Gardner Systems 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 Gardner Systems Data Requirements (Number, Type and Location of Sensors)

RHODES Gardner Systems Data Requirements (Number, Type and Location of Sensors) Prediction Generators Prediction Receiver

RHODES Gardner Systems 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 Gardner Systems 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 Gardner Systems Communications Requirements (Architecture, Polling Time, Bandwidth) Architecture - Alternatives –Token Ring –Ethernet –Point-to-Point, Tree Technology –Field Hardened –$$$

RHODES Gardner Systems Peer-to-Peer Communications: Tucson and Seattle Central Management System Communications Hub Intersection Controllers (2070 with MEN CPU) Optelecom 9712 Modem Pairs: Baud RS K Serial/PTZ 1 - Full Motion Video 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 Gardner Systems 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 Gardner Systems Hardware Requirements (Central, Intermediate Field, Local Processor) Central –PC-based traffic server (e.g. icons TM ) –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 Gardner Systems 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 Gardner Systems O&M Cost Ranges Incremental cost based on additional hardware (including detection) and software Cost savings based on improved signal timing