1. U.S. Department of Transportation Federal Highway Administration 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

2. U.S. Department of Transportation Federal Highway Administration Slide 2 Outline Goals System architecture Adaptive approach –Cyclic performance measures Field trials

3. U.S. Department of Transportation Federal Highway Administration Slide 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. U.S. Department of Transportation Federal Highway Administration Slide 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. U.S. Department of Transportation Federal Highway Administration Slide 5 Project Team

6. U.S. Department of Transportation Federal Highway Administration Slide 6 System Architecture Vendor Field Master Protocol Translation 9600bps, up to 12 controllers NTCIP + ACS-Lite firmware upgrade Vendor Specific or NTCIP NTCIP ACS-Lite Optional Field Processor

7. U.S. Department of Transportation Federal Highway Administration Slide 7 ACS-Lite Detection Layout Flow Profile Detectors Phase Utilization Detectors Need detectors at stop-bar of coordinated phases

8. U.S. Department of Transportation Federal Highway Administration Slide 8 2 1 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

9. U.S. Department of Transportation Federal Highway Administration Slide 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. U.S. Department of Transportation Federal Highway Administration Slide 10 Occupancy per phase interval Occupancy values per second Correlated to Red/Green/Yellow 37s4s49s Second-by-second Occupancy 37s4s32s Second-by-second Occupancy Cycle 1 Cycle 2 17s

11. U.S. Department of Transportation Federal Highway Administration Slide 11 Cycle-by-cycle Data Phase Timing Volume/Occupancy

12. U.S. Department of Transportation Federal Highway Administration Slide 12 Occupancy per interval  split tuning 57s4s29s Phase 2 Average Occupancy Unoccupied Averaging

13. U.S. Department of Transportation Federal Highway Administration Slide 13 Green occupancy  Phase Utilization

14. U.S. Department of Transportation Federal Highway Administration Slide 14 Cyclic occupancy profiles  Statistical profile “statistical” flow profile Example shows need to move offset so green corresponds with traffic earlier in cycle

15. U.S. Department of Transportation Federal Highway Administration Slide 15 Progression Performance  Offset tuning Performance measure for offsets  “capture efficiency” Shift offsets small amount Constrain changes within user-configurable bounds Inbound Outbound

16. U.S. Department of Transportation Federal Highway Administration Slide 16 Field trials PEEK St. Petersburg/Tampa, Florida Econolite Columbus, Ohio Eagle/Siemens Houston, Texas McCain San Diego, California

17. U.S. Department of Transportation Federal Highway Administration Slide 17 Field trial – Columbus, Ohio Early “lessons learned” –Communications integrity –Detector configuration Separate channels per lane –Remote configuration capability –Details, details High School Freeway 3km Major road Construction zone

18. U.S. Department of Transportation Federal Highway Administration Slide 18 Columbus, Ohio - Hamilton Road Study Area N

19. U.S. Department of Transportation Federal Highway Administration Slide 19 Columbus, Ohio – Hamilton Road (con’t)

20. U.S. Department of Transportation Federal Highway Administration Slide 20 ACS-Lite Field trial – Houston, Texas State Route 6 Study Area N

21. U.S. Department of Transportation Federal Highway Administration Slide 21 Houston, Texas – State Route 6 (con’t)

22. U.S. Department of Transportation Federal Highway Administration Slide 22 ACS-Lite Field trial – Tampa, Florida State Route 70 Study Area N

23. U.S. Department of Transportation Federal Highway Administration Slide 23 Tampa, Florida – State Route 70 (con’t)

24. U.S. Department of Transportation Federal Highway Administration Slide 24 ACS-Lite Field trial – San Diego, California Main Street N Study Area

25. U.S. Department of Transportation Federal Highway Administration Slide 25 San Diego, California – Main Street (con’t)

26. U.S. Department of Transportation Federal Highway Administration Slide 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. U.S. Department of Transportation Federal Highway Administration Slide 27 Questions?