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Trip Distribution Modeling Part II

Trip Distribution Modeling Part II. CE 573 Transportation Planning Lecture 13. Objectives. Trip length distribution Model constraints Converting to Origin-Destination (O-D) format. Trip Length Distribution (TLD). Survey of region traveler behavior frequency of trips

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Trip Distribution Modeling Part II

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  1. Trip Distribution Modeling Part II CE 573 Transportation Planning Lecture 13

  2. Objectives • Trip length distribution • Model constraints • Converting to Origin-Destination (O-D) format Michael Dixon

  3. Trip Length Distribution (TLD) • Survey of region traveler behavior frequency of trips • Perform gravity model • While executing gravity model… • Impedance function calibration is only good for the conditions used for calibration, given: Michael Dixon

  4. Trip Length Distribution (TLD) (coninued) • Alternative impedance functions Use this for our example Michael Dixon

  5. Gravity Model Example • Given the TLD of a survey • Input information from trip generation • Interzonal travel costs in minutes • Adopt an impedance function [ ] • Execute gravity model, calibrating impedance function Michael Dixon

  6. Gravity Model Example (HBW TLD) Michael Dixon

  7. Gravity Model Example (Trip Generation Information) Michael Dixon

  8. Gravity Model Example (Intrazonal Travel Costs) Interzonal Michael Dixon

  9. Gravity Model Example (Execution) • Step 1: Initialize Jbin values to a value of ‘1’ for all cost bins bin • Step 2: Relate all zone pairs to travel cost bins Michael Dixon

  10. Gravity Model Example (Execution) • Step 3: Calculate the trip distribution matrix • Step 4: Determine the estimated TLD • Step 5: Compare estimated TLD to observed TLD • Step 6: Calibrate the impedance function to reproduce the observed TLD • Repeat steps 3 to 6 until error is less than X% (say 5% for this example) Michael Dixon

  11. Gravity Model Example (Execution) (continued) Michael Dixon

  12. Converting to Origin-Destination (O-D) Format • Non-Home Based trip purposes, Production-Attraction (P-A) format = O-D format • Home-Based trip purposes P-A format ≠ O-D format, needs to be modified • The formula for converting is as follows: Michael Dixon

  13. Converting to Origin-Destination (O-D) Format (from Example) Michael Dixon

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