developing a sketch plan model for the southern california association of governments
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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
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
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
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
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
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)
Example of Network Realignment
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 /*
Zonal Aggregation Models
• Intra-Superzone Trips Model • To account for underassignment of
trips
This Trip
Becomes an Intrazonal Trip
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
Intra-Superzone Assignment ExampleAggregate OD Matrix Inter-Superzone
TripIntra-Superzone Trip
Correspondence Table Disaggregate Intra-Superzone Trip
Zonal Aggregation Models
• Superzone Connector Assignment • To better assign Inter-Superzone
Trips
Should really be thisShould really be this
This TripThis Trip
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
Demo of Sketch Plan Model
Model Run Times
• Regional Model – 24 hours• Full Sketch Plan Run – 2 hours• One-loop highway-only run – 75
minutes
Calibration Results
Calibration Results
Future Work
• Explore Random allocation of zones for skimming
• Add transit-only component• Integration with TDM and land use
models• Additional optimization
Thank You