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ACS-Lite FHWA Adaptive Signal Control Systems

ACS-Lite FHWA Adaptive Signal Control Systems. Raj S. Ghaman, P.E. Team Leader, Office of Operations RD & T Traffic Signal & Operations Working Group March 26, 2008 Washington D.C., USA. Outline. Goals System architecture Adaptive approach Cyclic performance measures Field trials.

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ACS-Lite FHWA Adaptive Signal Control Systems

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  1. ACS-LiteFHWA Adaptive Signal Control Systems Raj S. Ghaman, P.E. Team Leader, Office of Operations RD & T Traffic Signal & Operations Working Group March 26, 2008 Washington D.C., USA

  2. Outline • Goals • System architecture • Adaptive approach • Cyclic performance measures • Field trials

  3. Adaptive in the U.S. (FHWA) • 1970s-1980s: UTCS • Second by second central • 1990s: Predictive control (ACS) • FHWA ACS: RHODES, OPAC • Second by second distributed • 2002: Controller-based Adaptive • FHWA ACS “Lite”: Siemens ITS • Leverage existing hardware • Update controller parameters every five minutes

  4. FHWA Goals for ACS-Lite • Low cost design • Leverage existing infrastructure • Standard US-style actuated controllers (rings, phases, splits, barriers) • Standard fully-actuated detector layouts • Standard NTCIP Communications • “Retro-fit” with major US signal system vendors

  5. Project Team

  6. Protocol Translation System Architecture 9600bps, up to 12 controllers ACS-Lite Vendor Field Master Optional NTCIP Optional Vendor Specific or NTCIP Field Processor NTCIP + ACS-Lite firmware upgrade

  7. ACS-Lite Detection Layout Need detectors at stop-bar of coordinated phases Phase Utilization Detectors Flow Profile Detectors

  8. ACS-Lite adaptive control philosophy • Data-driven parameter tuning • Limited/no traffic modeling • Recent past predicts the near future • Splits • Phase Utilization • Offsets • Statistical Flow Profiles 1 2

  9. ACS-Lite NTCIP firmware upgrade • Phase Timing Status Object • Detector Status Object • Configuration Objects • Polled once per minute • Second-by-second accuracy • Bandwidth efficient • Minute-by-minute polls are “stitched” together for cycle-by-cycle performance assessment 1 2 3

  10. Occupancy per phase interval • Occupancy values per second • Correlated to Red/Green/Yellow Cycle 1 Second-by-second Occupancy 37s 49s 4s Cycle 2 Second-by-second Occupancy 37s 32s 4s 17s

  11. Cycle-by-cycle Data Phase Timing Volume/Occupancy

  12. Occupancy per interval split tuning Averaging Unoccupied Phase 2 Average Occupancy 29s 4s 57s

  13. Green occupancy  Phase Utilization

  14. Cyclic occupancy profiles  Statistical profile Example shows need to move offset so green corresponds with traffic earlier in cycle “statistical” flow profile

  15. Progression Performance  Offset tuning • Performance measure for offsets  “capture efficiency” • Shift offsets small amount • Constrain changes within user-configurable bounds Inbound Outbound

  16. Field trials Econolite Columbus, Ohio McCain San Diego, California Eagle/Siemens Houston, Texas PEEK St. Petersburg/Tampa, Florida

  17. Field trial – Columbus, Ohio Construction zone • Early “lessons learned” • Communications integrity • Detector configuration • Separate channels per lane • Remote configuration capability • Details, details Major road High School 3km Major road Freeway

  18. Study Area N Columbus, Ohio - Hamilton Road

  19. Columbus, Ohio – Hamilton Road (con’t)

  20. Study Area N ACS-Lite Field trial – Houston, Texas State Route 6

  21. Houston, Texas – State Route 6 (con’t)

  22. ACS-Lite Field trial – Tampa, Florida State Route 70 N Study Area

  23. Tampa, Florida – State Route 70 (con’t)

  24. ACS-Lite Field trial – San Diego, California Main Street N Study Area

  25. San Diego, California – Main Street (con’t)

  26. Future • Algorithms enhancements (2008): • Long-term parameter adjustment • Seasonal baseline parameters • TOD schedule switch points • Cycle time tuning • Selection of transition method • Better Graphical User Interface (GUI)

  27. Questions?

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