11th TRB Planning Applications Conference

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Simulation-Based Equilibrium Assignment
Insights and Future Challenges

• Michael Mahut, Michael Florian and Nicolas
  Tremblay
• INRO
• Montreal, Canada

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Agenda

• Overview of DTA
• Bakersfield Project
• Calibration approach
• Advances in assignment methodology
• Conclusions

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Types of DTA models

• microsimulation
• car following
• gap acceptance
• lane changing

microsimulation
highfidelity
fluid / CTM
lowfidelity
volume-delay constraints
one-pass
iterative
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Equilibrium DTA
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Agenda

• Overview of DTA
• Bakersfield Project
• Calibration approach
• Advances in assignment methodology
• Conclusions

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Network
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Calibration Data

• Data provided
• 2005 turning movement counts (16 major
  intersections)
• 2005 Route 99 car and truck counts
• 2006 AM PM qualitative queuing observations
• Other potential data
• speed measurements
• travel time probes

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Network
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Link Flows
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Relative Gaps
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Calibration Results

• interval slope R2
• 715-730 0.96 93
• 730-745 0.91 89
• 745-800 0.91 88
• 800-815 1.07 91
• 815-830 1.09 91
• 830-845 1.17 89

• interval slope R2
• 415-430 1.05 91
• 430-445 1.01 89
• 445-500 1.03 89
• 500-515 0.94 88
• 515-530 0.89 86
• 530-545 1.04 86

predicted flows
counts
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Queues
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Performance

• Demand
• 4x30-minute matrices, 2 classes
• Trips
• 61000 (car) 2900 (truck)
• RAM
• 80 MB
• CPU ? Speed-up
• per iteration 66 sec ? 110x
• full DTA 77 min ? 1.6x

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Agenda

• Overview of DTA
• Bakersfield Project
• Calibration approach
• Advances in assignment methodology
• Conclusions

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Link Flows
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Select Link
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Path Flows
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Agenda

• Overview of DTA
• Bakersfield Project
• Calibration approach
• Advances in assignment methodology
• Conclusions

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MSA Improvements

• general observation
• MSA can be slow in removing flow from
  unattractive paths
• (1) dynamic reset
• Step-size increases with increasing departure
  interval
• (2) quasi-gradient
• Path-flow adjustment by O-D based on
  quasi-gradient
• Step size applied to total displaced flow (O-D)

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MSA
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Gradient Reset
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Agenda

• Overview of DTA
• Bakersfield Project
• Calibration methodology
• Advances in methodology
• Conclusions

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Conclusions

• Micro-simulation based DTA (Dynameq)
• can be applied to medium-sized networks and
  calibrated with reasonable effort
• Calibration
• demand side (path and O-D) causes quickly
  identified using Select Link and Path Analysis
  tools
• Consistency (Reproduce-ability)
• Changes to demand or supply lead to reasonable
  (commensurate) changes to model outputs
• Equilibrium property is critical!

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