ASCT and Systems engineering

1. ASCT and Systems engineering Edward Fok, PE, PTOE FHWA Office of Technical Service/Resource Center

2. Adaptive Signal Control Topics • Operational Objectives • Systems Engineering • A Couple of Relevant Federal Regulations(if Federal Funds are used)

3. Objectives • Shift by time of day, and over time: • Pipeline vs. land-use access • Progression even possible? • Congestion: Throughput • Congestion: Queue management • What is making the phone ring? • Adaptive signal control continuously adjusts operation to measured conditions

4. The Role of Systems Engineering • 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)

5. Usual Systems Engineering Process • Define needs (Concept of Operations) • Extract requirements from needs • Design and implement to fulfill requirements • Test against requirements (verification) • Test against actual use (validation)

6. Purpose of SE Model Documents • Usual process too much work for small projects… • …but small projects still impose big risk to small agencies • Model documents greatly reduce effort by providing wording and documentation… • …but agencies still must identify their needs

7. Model Document Process • Answer a series of questions • Evaluate constraints • Ask questions again with different constraints

8. Questions • What is the size of the network that needs to operate adaptively, initially and in the future? • In the absence of adaptive control, what is the best operation? • What are the operational objectives for the signals to be coordinated? • If there are crossing arterials, how will compatibility be maintained?

9. Questions • How will borders with other systems and institutions be handled? • Do you need more than standard 8-phase operation? • Are queues outside the control of your system? • How should pedestrians be accommodated by the adaptive system?

10. Questions • Are there situations that may lead you to sometimes require non-adaptive control? • What form of monitoring and system control is required? • Will architecture constraints limit control options? • What performance reporting do you want?

11. Questions • How will notification of failure of the adaptive system be managed? • Is pre-emption or transit priority required to operate during adaptive operation? • What failure modes are required? • Sustainability requirements—complexity, software maintenance, staffing, databases, maintenance response times

12. Model Document Products • Scenarios for Concept of Operations • Basis for understanding organizational needs • Well-formed, testable requirements traced to needs • Basis for product choices • Basis for procurement documents • Basis for testing and acceptance • Sample project architecture

13. Example-Handling Crossing Streets • “If there are crossing arterials, how will compatibility be maintained? • Make them part of the operation, but remain separate systems • Make them part of the system • Constrain the adaptive system to respond to the operation of the crossing arterial”

14. Guidance for Choice 1 “Part of the operation • In this arrangement, the signals operating on the crossing arterials would not be part of the adaptive system. However, they would operate in a manner consistent with the adaptive system. This could be achieved by…”

15. Adaptive Scenario, Choice 1 • “A. Part of the operation • The adaptive system optimizes its operation on an arterial in accordance with its own objective functions. It then communicates key data to the adjacent systems operating other intersections, and those systems adjust their operation to maintain consistency with the adaptive system. This would typically involve sending cycle length and offset data to the other systems.”

16. Requirements Example • “…communicates key data to the adjacent systems…” leads to • The system shall export data • The data shall include cycle length • The data shall include cycle reference point • The data shall include offset of current cycle • The data shall include offset of next cycle • The export interface shall conform to NTCIP… • The system shall make export data available every second • And so on…

17. 23 CFR 940.11 Required SE Analysis • Portions of Regional Architecture being implemented (Model Project Architecture) • Roles and responsibilities of participating agencies (Scenario) • Requirements definitions • Analysis of alternative system configurations and technology options to meet requirements (Design choices) • Procurement options (Implementation options) • Identification of applicable ITS standards and testing procedures (Verification and Validation) • Procedures and resources necessary for operation and management of the system (Needs)

18. Procurement Regulations • Proprietary Materials (23 CFR 635.411) • Certification of no available competitive product • Uniquely fulfills the requirements imposed on the product • Achieves synchronization with existing systems • Public Interest Finding for proprietary purchase despite alternative available competitive products • Limited experimental application • Systems Engineering provides justification