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PRT System Capacity

CARBON-FREE MOBILITY CONFERENCE. PRT System Capacity. March 6, 2009 J. Sam Lott, P.E. Kimley-Horn and Associates, Inc. Presentation Overview. Capacity – Defining the Issues Station Operations Main Line Station/Main Line Transition Zone Vehicle Occupancy Conclusions.

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PRT System Capacity

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  1. CARBON-FREE MOBILITY CONFERENCE PRT System Capacity March 6, 2009 J. Sam Lott, P.E. Kimley-Horn and Associates, Inc.

  2. Presentation Overview • Capacity – Defining the Issues • Station Operations • Main Line • Station/Main Line Transition Zone • Vehicle Occupancy • Conclusions

  3. Capacity – Defining the Issues

  4. Capacity – Defining the Issues • Safety • Operational sustainability • Failure mode recovery/work-around • Redundant elements: More is not necessarily better • Public perception may negate some solutions

  5. Station Operations

  6. Station Operational Capacity – A premise for the near term As important as line capacity issues are, the successful application of PRT systems will be determined by the practical and sustainable operational capacity limits of the stations serving the peak demand conditions of the system. Ref. 2006 PT Expo “PRT Stations – System Capacity Implications” by J. Sam Lott and Jill Capelli

  7. Operational Concept and Station Configuration • Serial Station Berths • FIFO with head-end loading position(s) • FIFO with platooning and simultaneous loading positions • Parallel Station Berths • Parallel In-Line • Parallel Only Berths

  8. Serial Berths - Head End Load Unload only Positions Load and Unload Positions

  9. Serial Berths – Platooning Unload/ Load Berths Dispatch Track Staging Positions Receiving Track Staging Positions

  10. Parallel Berths – In Line Parallel Berth Station Guideway Mainline Guideway

  11. Parallel Berths – With Reversing Parallel Berths Unload/ Load Berths Dispatch Track Staging Positions Serial Berths Receiving Track Staging Positions

  12. Conclusions on Station Capacity Dwell time is #1 variable • 2 to 20 sec. in theoretical studies, but passenger interactions could increase these values • Communication of loading berth location is complicated for visually impaired passengers • Extended dwell times required for elderly and handicapped • Loading and unloading of baggage significantly impacts dwell times

  13. Conclusions on Station Capacity Number of loading berths #2 variable • Station dimensions are a practical limit Berth configuration (serial berths versus parallel berths) is #3 variable • Parallel berths reduce dwell and reliability impacts, but slow down operating speeds

  14. Conclusions on Station Capacity For the first PRT Systems we will implement (i.e., next ten years), the following are proposed practical maximums for planning purposes: • Single-sided stations • 6 to 8 berths • 500 to 1000 vehicles/hr • 1000 to 2000 passengers/hr

  15. Main Line

  16. Main Line Capacity Mainline throughput capacity issues include: • Sustainable operating headway • Empty vehicle mix • Average passenger occupancy of loaded vehicles Ref. 2005 TRB “Capacity Analysis of Demand Responsive Systems” by J. Sam Lott and David S. Tai

  17. Operating Headway Determined by: • Synchronous control means that provides space (or “slot”) for merging vehicles to enter the Main Line flow • Brick wall stop safety criteria • Sustainable average spacing between vehicles that accounts for operational perturbations – i.e., the real world

  18. Station/Main Line Transition Zone

  19. Designations of Operating Zones • Station Guideway – Low speed operations with special train control considerations • Main Line Guideway – Full speed operations under ATP safety functions • Station/Main Line Transition Zone – Acceleration/deceleration zones where hand-off occurs between Station and Main Line control functions

  20. Vehicle Occupancy

  21. Vehicle Occupancy • Determined by the local demographic effect on travel party size (e.g., % of families) • Shared ride options heavily effected by: • Safety culture and physical context • Trip patterns conducive to shared ride • Surge flow characteristics • Empty vehicle management and storage locations drive the mix of empty vehicles A new ASCE APM Conference paper by Ingmar Andréasson addresses some of these aspects

  22. Conclusions

  23. Is Capacity a Big Deal? YES Message to Owners/Developers – PRT is ready for consideration, however: • Suitability must be determined for each specific application • Operations are very complex • Hidden capacity constraints can exist • Solutions applying redundant elements may penalize PRT effectiveness

  24. Is Capacity a Big Deal? YES Message to Planners/Suppliers – PRT is ready for consideration, however: • Don’t force fit PRT to all applications • Be patient and let PRT technology mature before assuming capacity capabilities • Listen to what transit professionals have learned through experience

  25. Is Capacity a Big Deal? YES Message to Transit Professionals – PRT is ready for consideration, however: • Capacity vs. safety issues are critically important to understand • Consider the world-wide design context • Be open minded, while remaining protective of passenger safety

  26. PRT System Capacity March 6, 2009 J. Sam Lott, P.E. Kimley-Horn and Associates, Inc.

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