PRT%20System%20Capacity

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

• Capacity Defining the Issues
• Station Operations
• Main Line
• Station/Main Line Transition Zone
• Vehicle Occupancy
• Conclusions

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Capacity Defining the Issues
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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

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Station Operations
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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

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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

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Serial Berths - Head End Load
Unload only Positions
Load and Unload Positions
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Serial Berths Platooning
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Parallel Berths In Line
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Parallel Berths With Reversing
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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

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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

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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

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Main Line
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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

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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

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Station/Main Line Transition Zone
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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

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Vehicle Occupancy
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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

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Conclusions
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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

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Is Capacity a Big Deal? YES

• Message to Planners/Suppliers
• PRT is ready for consideration, however
• Dont 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

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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

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