RHODES and Next Generation RHODES

RHODES and Next Generation RHODES Pitu Mirchandani ATLAS Research Laboratory Arizona State University Is adaptive right for you? Panel ITE Meeting, Phoenix March 9, 2011 Acknowledgements: David Lucas, Larry Head, Steve Shelby, Doug Gettman, Suvrajeet Sen,, plus FHWA, ADOT, Tucson, Tempe, NSF

Outline 2-part talk Current Traffic Control Issues Response of RHODES: Real-time Adaptive Control RHODES - Next Generation Further Response to Issues Current Issues -- RHODES -- RHODES/NG -- Conclusions

What is an Adaptive Control System? It is necessarily a Feedback Control System that Adapts data Real-time Control System Sensors and Measurements: monitoring state of system Feedback & decisions Actual System Controls: Actuators Signals. Current Issues -- RHODES -- RHODES/NG -- Conclusions

Simplified Architecture for RHODES Data collection and prediction of queues and arrivals raw data processed data Control Selection Feedback & decisions Detectors, traffic signals, and communication Control Actions (phase durations) We are showing only Counts loop detectors but any sensor Stop-bar will work Current Issues -- RHODES -- RHODES/NG -- Conclusions

Issues with Conventional Traffic Control (TOD/Actuated) Although traffic signals manage the safety and traffic performance of the limited capacity of an intersection, little recognition that traffic is a fluctuating stochastic process. E.g.: A traffic plan (cycles, splits and offsets) assumes a stationary stochastic process. Note: RHODES does not use plans but estimates realtime information to provide green time to movements being demanded. (Will discuss shortly). Current Issues -- RHODES -- RHODES/NG -- Conclusions

TRAFFIC CONTROL ISSUES and RESPONSES ISSUES Limited Intersection Capacity TOD/Actuated RHODES RHODES-NG Safety Traffic Performance Widely Fluctuating Traffic Preemption & Priority Oversaturation Ease of Implementation Cost Installation $$ $$$ $$ Cost Maintenance $$$ $$ $ Very Good Okay Very Bad Current Issues -- RHODES -- RHODES/NG -- Conclusions

Quality Attributes of an Adaptive Traffic Signal Control System? Responsiveness: How fast does it respond to changes in traffic conditions? (including incidents and special events) Feedback Philosophy: Is it reactive? (the vanilla version) Is it proactive? (the sundae version) Current Issues -- RHODES -- RHODES/NG -- Conclusions

Open-loop, Reactive & Proactive (Illustration in following a trajectory) Position Actual Trajectory Reactive Open Loop Proactive Time Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES (Proactive) Traffic Control Explicitly recognizes that traffic state is a fluctuating stochastic process Requires prediction of short-term future based on current conditions and controls Especially useful for non-recurrent traffic conditions and major incidents Current Issues -- RHODES -- RHODES/NG -- Conclusions

TRAFFIC CONTROL ISSUES and RESPONSES ISSUES Limited Intersection Capacity TOD/Actuated RHODES RHODES-NG Safety Traffic Performance Widely Fluctuating Traffic (need prediction) & Priority Oversaturation Ease of Implementation Cost Installation Cost Maintenance $$ $$$ $$$ $$ $$ $ Very Good Okay Very Bad Current Issues -- RHODES -- RHODES/NG -- Conclusions

PREDICTION & CONTROL IN RHODES PREDICT arrivals & queues CONTROL ALGORITHMS (CAPRI) TURN RATIOS TRAVEL TIMES DISCHARGE RATES detectors state of traffic network Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES: INTERSECTION PREDICTION UNDER RHODES CONTROL ca rdetector Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES: INTERSECTION PREDICTION And... PREDICTIONS! Next second A little later R.3 1.3.6.3.3.3.3.3.3 T 1.5 2 1.5 2 1.5.5.5.5.5.5 L.2 1.2.4.2.2.2.2.2.2 1 2 3 4 45 46 47 48 49 50 51 52 Time Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES INTERSECTION CONTROL R T L R T L R T L R T L 1 2 1.6 2.4.3 1.5.2.3.5.2.3.5.2 1 2 3 4 45 46 47 48 49 50 51 52 PHASE ORDER: B-C-D-A-B-C-D-A... B C D A B C.3.5.2.3.5.2.3.5.2 From North From South From West From East Time We can easily compute total delay and stops from this diagram RHODES idea is to choose Phase durations to max. performance. 1 2 3 4 45 46 47 48 49 50 51 52 Time

Performance - Simulation (Atlanta) SAC RHODES Current Issues -- RHODES -- RHODES/NG -- Conclusions

Additional Features - Transit Priority NETWORK FLOW CONTROL SUBSYSTEM APRES-NET arrivals & queues REALBAND INTERSECTION CONTROL SUBSYSTEM PREDICT TRAVEL TIMES TURN RATIOS arrivals & queues CAPRI DISCHARGE RATES detectors Transit/bus Priority (position and weight ) Current Issues -- RHODES -- RHODES/NG -- Conclusions

Additional Features - Emergency Preemption NETWORK FLOW CONTROL SUBSYSTEM APRES-NET arrivals & queues REALBAND INTERSECTION CONTROL SUBSYTEM DISCHARGE RATES PREDICT TRAVEL TIMES detectors TURN RATIOS arrivals & queues CAPRI Emergency vehicles (phase constraints) Current Issues -- RHODES -- RHODES/NG -- Conclusions

OTHER ISSUES Few jurisdictions use adaptive control mainly because They are hard to implement need little more training Require additional sensors about the same as actuated but more communication (from upstream to downstream) Maintenance? if sensors are reliable then re-timing maintenance is decreased Improve performance only when system is under saturated will discuss oversaturation soon Current Issues -- RHODES -- RHODES/NG -- Conclusions

TRAFFIC CONTROL ISSUES and RESPONSES ISSUES Limited Intersection Capacity Safety Traffic Performance Widely Fluctuating Traffic Preemption & Priority TOD/Actuated RHODES Oversaturation Ease of Implementation Cost Installation $$. $$$ Next- Generation RHODES Cost Maintenance $$$ $$ Very Good Okay Very Bad Current Issues -- RHODES -- RHODES/NG -- Conclusions

2 nd Part Current Traffic Control Issues Response of RHODES: Real-time Adaptive Control RHODES - Next Generation Further Response to Issues Current Issues -- RHODES -- RHODES/NG -- Conclusions

The performance of RHODES is directly related to the accuracy of its queue estimates Parameters which affect this accuracy: Turn Proportions RHODES Input Parameters Proportion of vehicles on an approach which turn left, turn right or proceed through the intersection Queue Discharge Rates Rate at which vehicles leave an intersection, dependent upon the number of available lanes and the movement involved Link Travel Times Time taken by a vehicle to traverse the distance from an upstream peer intersection to a point downstream Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES Self-Adaptive Traffic Signal Control Self-adaptive Traffic Signal Control Next Generation RHODES incorporate algorithms that automatically update critical RHODES parameters based on available data Benefits Performance of RHODES will be further improved Significant reduction in calibration and fine-tuning Eliminates the need to update parameters periodically Data and computed parameters (from RHODES) will be available to agencies for other purposes, such as regional planning Current Issues -- RHODES -- RHODES/NG -- Conclusions

INTERSECTION CONTROL SUBSYTEM PREDICT arrivals & queues CAPRI TURN RATIOS DISCHARGE RATES TRAVEL TIMES GENERALIZED LEAST-SQUARE ESTIMATION detectors Current Issues -- RHODES -- RHODES/NG -- Conclusions

INTERSECTION CONTROL SUBSYTEM PREDICT arrivals & queues CAPRI TURN RATIOS TRAVEL TIMES DISCHARGE RATES detectors REAL-TIME PLATOON TRACKING Current Issues -- RHODES -- RHODES/NG -- Conclusions

INTERSECTION CONTROL SUBSYTEM PREDICT arrivals & queues CAPRI TRAVEL TIMES TURN RATIOS THIS IS SUPPORTED BY AN ON-GOING FHWA CONTRACT DISCHARGE RATES detectors Current Issues -- RHODES -- RHODES/NG MONITORING ESTIMATED QUEUES & DETECTOR OCCUPANCIES -- Conclusions

RHODES Self-Adaptive Traffic Signal Control Self-adaptive Next Generation RHODES responds to oversaturation 1. From residual queues it recognizes saturation regimes (next slide) 2. From upstream-downstream communication RHODES spreads the queues, keeping traffic stable. 3. But note: that there is always a capacity for a signalized network, and when the load is increased above this capacity there will be unbounded queues. Gating into network is necessary for keeping queues bounded. Current Issues -- RHODES -- RHODES/NG -- Conclusions

RHODES Self-Adaptive Traffic Signal Control Automatically recognizes various operating regimes Queue size Residual queues keep exploding (over saturation) Usually no residual queues Residual queues described by steady-state distribution Traffic load Current Issues -- RHODES -- RHODES/NG -- Conclusions

TRAFFIC CONTROL ISSUES and RESPONSES ISSUES Limited Intersection Capacity TOD/Actuated RHODES RHODES-NG Safety Traffic Performance Widely Fluctuating Traffic Preemption & Priority Oversaturation Ease of Implementation Cost Installation $$. $$$ $$ Cost Maintenance $$$ $$ $ Very Good Okay Very Bad Current Issues -- RHODES -- RHODES/NG -- Conclusions

Concluding Remarks on Next Generation RHODES Control Improvement in traffic performance: responds to recurrent congestion responds to near oversaturation responds to non-recurrent conditions and incidents (through monitor, learn, predict and optimally respond strategy) Decrease in traffic operations/planning effort operators need not time signals periodically planners and traffic engineers can concentrate on smaller number of scenarios Current Issues -- RHODES -- RHODES/NG -- Conclusions

Thanks for your attention Questions???

Possible Questions 1 and 2 Benefits compared to TOD/Actuated: main part of my talk Are there certain conditions when traditional TOD plans are more beneficial than your Adaptive TCS? No! When the traffic demand becomes stationary the phase durations become similar to a well timed semi-actuated control.

Possible Questions 3 Has a cost to benefit analysis been done for your Adaptive TCS? Yes! Third party evaluation at Pinellas Co. showed that Main corridor showed significant operational improvements, with very slight cross street penalties Total lifecycle savings over 10-yr period was $10.6M, B/C ratio 7.7 Average reductions: travel time: 5-15% stops: 10-24% delay: 9-39%

Possible Questions 4 What are the basic steps in installing your system? Current RHODES requires: A single board computer (SBC) to house it, now using Gecko Board with Windows OS. (Now porting to Linux). 2070 ATC running Siemen s NextPhase or Econolite ASC with an adapt interface. But we are creating a public API for other controllers. Reliable communication network. E.g., intranet between peer intersections RHODES now fully integrated with MIST traffic mgt. system. It can monitor RHODES status and upload/ download intersection layout and parameters RHODES has worked in TS1, TS2, and 170 cabinets.

Possible Questions 4 (contd) What are the basic steps in installing your system? Current RHODES by April can be run On 2070-1C engine board, eliminating need for SBC Also run centrally, where data from field will be operated on a central server which will download adaptive timings. In this case we need a high-speed communication network. (This approach could be used for trying out RHODES before investing in field equipment.)

Possible Questions 5 Once installed, what tasks are required to maintain it? typical maintenance tasks of inspecting detectors and communications systems. Until RHODES-NG is ready, need TOD turning ratios and any improvements or capacity changes to increase or decrease free flow travel times. (After RHODES-NG it is assumed all these parameters will be selfcorrecting.)

Possible Questions 4 (contd) What are the basic steps in installing your system? Current RHODES requires: Once hardware in place need to configure RHODES for each intersection which involves: Obtaining lane layout (number of lanes, length of turn bays, etc.) and inputting related parameters. (half of these used in TOD) Obtaining detectors layout and inputting related parameters (also used for TOD) Obtaining traffic data and inputting related parameters (also used in TOD) Tuning parameters to see if they were right (e.g., was the travel time right?) (also done in TOD) Qualitatively observe if RHODES seems to be working (also done in TOD)

RHODES Installations RHODES Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion

Additional Features - Emergency Preemption Location of incident reported Shortest route computed based on real-time traffic conditions and given to dispatcher Traffic signals pre-empted based on shortest route from depot to incident Depot Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion

Additional Features - Rail Preemption Train movement (position and schedule) NETWORK FLOW CONTROL SUBSYSTEM APRES-NET arrivals & queues REALBAND INTERSECTION CONTROL SUBSYTEM DISCHARGE RATES PREDICT TRAVEL TIMES TURN RATIOS arrivals & queues CONTROL ALGORITHMS Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion

Adaptive Turn Proportions Auto configuration based upon intersection geometrics/phasing Auto adjusts to reflect actual turn proportion variability Simulation results show an improvement in performance

Adaptive Turn Proportion Sample Results Approach-1-through movement turning pro oportion 1.2 1 0.8 0.6 0.4 0.2 0 algorithm's prediction three cycle's average 241 754 1187 1664 2155 2600 3269 3787 4433 5030 5929 time Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion

Simulation Results Without Turning Proportions Estimation Vehicle Vehicle Vehicle Travel time Avg. speed Avg. stop minutes Miles Trips Delay (Sec/Veh -Trip) (MPH) (Per Trip) time Period 1 3059 6711 3576 80.3 20.4.7 Period 2 5474 12304 5737 75.1 21.3.7 Period 3 8002 18369 8292 73.0 21.5.6 With Turning Proportions Estimation Vehicle Vehicle Vehicle Travel time Avg. speed Avg. stop minutes Miles Trips Delay time (Sec/Veh -Trip) (MPH) (Per Trip) Period 1 3058 6712 3039 75.4 21.7.6 Period 2 5467 12284 4760 70.4 22.8.6 Period 3 7979 18315 7386 70.1 22.4.6 Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion

Self-adaptive Traffic Signal Control Automatically recognizes various operating regimes Queue size Load info provided from upstream to downstream (usually no residual queues) Illustrated this earlier Residual queues keep exploding (over saturation) (residual queues described by steady-state distribution) Queue build info provided from downstream to upstream* Traffic load [* info on end of queue to prevent spill-back at upstream intersection]

Additional benefit: performance monitoring Queues, delays and travel times, Level of congestion operational regimes Unsaturated Saturated but stable Over saturated (unstable) Route travel times

Concluding Remarks NEAR FUTURE: Special vehicles will be identified via transponders and detectors, e.g.: Emergency, Transit, HAZMAT, using IntelliDrive structure Traffic signals will provide appropriate signal service by scheduling the service within the given time horizon FAR FUTURE: Every vehicle will be tracked. Every vehicle will be require and be provided appropriate service and treated with appropriate priority. Signals will provide in-vehicle signal and controls ( STOP or you will have an accident ). Safety will improve. Current Adaptive Control RHODES RHODES/NG RHODES/VII Conclusion