developing a sketch plan model for the southern california association of governments
DESCRIPTION
Developing a Sketch Plan Model for the Southern California Association of Governments. Jim Lam, Caliper Corporation Guoxiong Huang, SCAG Mark Bradley, BB&C Rich Kuzmyak Hong Kim TRB Applications Conference, May 18, 2009. Outline. Goal of the Sketch Plan Model Project - PowerPoint PPT PresentationTRANSCRIPT
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Developing a Sketch Plan Model for the Southern California Association of Governments
Jim Lam, Caliper CorporationGuoxiong Huang, SCAG
Mark Bradley, BB&CRich Kuzmyak
Hong KimTRB Applications Conference, May 18, 2009
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Outline
• Goal of the Sketch Plan Model Project• Sketch Plan Model Simplifications• Zonal Aggregation Models• Other Sketch Plan Features• Sketch Plan Demo• Model Run Times• Calibration Results• Future Work
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Goal of the Sketch Plan Model Project
• Current Regional Model is 4000+ zones and takes 24 hours to run
• To create a sketch planning version of the regional travel demand model
• Tool will be a quick response tool for testing a wide range of policies and projects to assess their benefits for the region.
• Tool will be simpler to run, much faster in execution, but be sufficiently accurate to identify beneficial projects for further detailed analysis with the full model.
• Keep model code consistent with Regional Model
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Sketch Plan Model Simplifications
• Aggregate TAZs to a simpler zonal structure
• Option to “skip” major portions of the model, such as transit
• Reduce input and output files, and reduce user-controllable model parameters
• Create a simplified interface• Reduce feedback loops and one-loop
model run• Simplify networks*• Mode split simplification*• Trip purpose reductions*• Vehicle ownership category
reductions** Models considered but ultimately not adopted
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Zonal Aggregation Models
• Zones reduced from 4109 to 302 zones, networks remained the same size
• Network centroid connectors realign to “Superzones” and networks re-skimmed for 302 zone system
• Extra models necessary to account for aggregation bias and for trip loss during aggregation (Zonal Allocation and Zonal Aggregation Models)
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Example of Network Realignment
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Zonal Aggregation Models• Zonal Allocation Model to determine
best “skim” for aggregated OD pair• Random choice model
• Randomly chosen OD pair from Regional skims for consistency with Regional estimations
• Problem: Need more than one random chosen pair to reduce variability, which reduces performance
• Randomness causes variability of results in alternatives analysis
• Weighted zonal allocation model• Superzone centroid location is chosen based
on HH and Emp weights allTAZ
iallTAZ
ii HouseholdHouseholdLongitudeLongitude /*
allTAZ
iallTAZ
ii HouseholdHouseholdLatitudeLatitude /*
allTAZ
iallTAZ
ii EmploymentEmploymentLongitudeLongitude /*
allTAZ
iallTAZ
ii EmploymentEmploymentLatitudeLatitude /*
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Zonal Aggregation Models
• Intra-Superzone Trips Model • To account for underassignment of
trips
This Trip
Becomes an Intrazonal Trip
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Zonal Aggregation Models
• Intra-Superzone Trips Model • Divide OD trips into Inter-
Superzone and Intra-Superzone trips from original correspondences
• Expand Intra-Superzone trips into original TAZ trip matrix using base OD matrices and IPF
• Separately assign Inter-Superzone trips and Intra-Superzone trips
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Intra-Superzone Assignment ExampleAggregate OD Matrix Inter-Superzone
TripIntra-Superzone Trip
Correspondence Table Disaggregate Intra-Superzone Trip
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Zonal Aggregation Models
• Superzone Connector Assignment • To better assign Inter-Superzone
Trips
Should really be thisShould really be this
This TripThis Trip
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Other Sketch Plan Features
• Automatically create Sketch Inputs from Regional Inputs
• Provide a simple interface• Simply define alternative scenarios• Simply run and compare multiple
scenarios
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Demo of Sketch Plan Model
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Model Run Times
• Regional Model – 24 hours• Full Sketch Plan Run – 2 hours• One-loop highway-only run – 75
minutes
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Calibration Results
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Calibration Results
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Future Work
• Explore Random allocation of zones for skimming
• Add transit-only component• Integration with TDM and land use
models• Additional optimization
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Thank You