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Adaptive Signal Control Technology: Bringing a Systems Approach to Implementation and Evaluation October 18, 2011

Adaptive Signal Control Technology: Bringing a Systems Approach to Implementation and Evaluation October 18, 2011. Kevin Fehon, P.E., PTOE DKS Associates. Overview. The past 40 years of adaptive signal systems The last five years in the USA Breaking out in 2011

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Adaptive Signal Control Technology: Bringing a Systems Approach to Implementation and Evaluation October 18, 2011

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  1. Adaptive Signal Control Technology: Bringing a Systems Approach to Implementation and EvaluationOctober 18, 2011

    Kevin Fehon, P.E., PTOE DKS Associates
  2. Overview The past 40 years of adaptive signal systems The last five years in the USA Breaking out in 2011 Bringing a structure to system selection Performance Evaluation
  3. First a definition ASCT – Adaptive Signal Control Technology Terminology adopted by FHWA Used to refer generically to adaptive traffic signal systems Avoids confusion with ACS-Lite
  4. The past 40 years It all started with SCATS in 1973 and SCOOT in 1975 Two fundamentally different but practically-oriented approaches Both widely accepted outside the USA by 1985 Different approach attempted in USA, reflecting different administrative and economic environment
  5. SCOOT 2009
  6. SCATS 2009 53 Cities; 179 Signal Regions
  7. What has held up acceptance in the USA? Agency capability and willingness System performance and benefits Lack of understanding Cost Availability of US-based systems
  8. Growing acceptance in the USA. ASCT is an important element of FHWA’s Every Day Counts (EDC) program Increasing number of jurisdictions considering ASCT Modern equipment with more processing power New ASCT systems emerging Still less than 1% of USA signals
  9. US Adaptive Systems, April 2011
  10. Systems currently available in USA SCOOT/TACTICS SCATS InSync LADOT ATSC ACS-Lite OPAC KHAdence QuicTrac RHODES Balance Synchro Green RHODES ATMS.now Delcan & Intellight

  11. Introducing a structured approach to ASCT system selection

  12. What is an appropriate definition of “adaptive”? Many different definitions are acceptable The definition you choose should be the one that suits your circumstances How do you define real-time? Is it predictive or reactive or both? What parameters are “adaptive”?

  13. What are you trying to achieve with ASCT?

  14. Different coordination strategies Most coordination strategies can be categorized in one of the following four ways: Pipeline along a route (arterial or within grid) Progression in two directions along a route Equitable service for adjacent land uses Queue management
  15. Non-coordination strategies Some adaptive strategies do not involve coordination Optimal operation of an isolated intersection Optimal operation of a single critical intersection within a coordinated area

  16. Why use a systematic process?

  17. Why SE? Understanding the problem Managing risk Projects getting bogged down with shifting requirements Acquisitions being challenged by unsuccessful bidders/proposers/vendors Projects not meeting agency needs (and it is mandatory for federal-aid projects)
  18. Are you fully expressing your desires? Is ASCT really what you need? Can you clearly document the deficiencies of your existing system that you wish to overcome with adaptive? Can you clearly document the existing capabilities of your system that must be retained with adaptive operation?
  19. Can you clearly verify that you got what you asked for? Are your needs clearly expressed? Is each need translated into a requirement Is every requirement actually satisfying an expressed need? How is each requirement tested, so the that the vendor can verify it is satisified?
  20. Can you validate that you got what you needed? Have your organization’s goals and objectives been clearly defined? Are measures of performance clearly defined? Can you test the operation against the measures of performance?

  21. What is the purpose of the Model Systems Engineering Documents?

  22. Provide a framework to guide agencies to the most appropriate solution Provide sample statements that can be used in a Concept of Operation Provide sample requirements that can be used to select/purchase/design a system Describe appropriate verification and validation plans

  23. How should your process work?

  24. Overview First pass in half to one day, by experienced agency staff Identify additional information you need in order to make appropriate decisions and document the basis of those decisions
  25. Work Flow

  26. What are the pitfalls of not following a structured approach?

  27. Pitfalls You don’t get the most suitable system You may lose some capabilities You may not get the system you want Making a constraint a requirement at the outset distorts the outcome. You can’t quantify the trade-offs you are making
  28. The structured approach will result in the most appropriate ASCT selection Required capabilities will be clearly stated Assumptions will be explicit, so requirements won’t fall through the cracks Trade-offs to satisfy real and perceived constraints will be explicit and justified Expectations are more likely to be met
  29. Is it worth the effort? Emphatically yes! Some ASCT systems that have not fulfilled expectations are falling by the wayside The established systems have strongly documented benefits and high B/C ratios Much misinformation, both positive and negative
  30. Gresham PM Peak TT(Eastbound Burnside) Legend 1997 Free 1998 TOD 2004 Free 2004 (1998 TOD) 2004 TOD 2007 (2004 TOD) 2007 SCATS 500 424 405 393 373 400 368 349 Travel Time (sec) 314 300 200 100 0
  31. Evaluation techniques often hide the truth Travel time per direction does not show system-wide effects, and confuses positive and negative impacts. Travel time per period do not show effects of varying demand levels. Volume-weighted, system-wide evaluation allows differentiation of conditions.
  32. Sunnyvale: System Expansion

  33. Questions?

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