1. 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

2. 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

3. Goal of the Sketch Plan Model Project
Current Regional Model is 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

4. 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

5. 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)

6. Example of Network Realignment

7. 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

8. Zonal Aggregation Models
Intra-Superzone Trips Model
To account for underassignment of trips
This Trip
Becomes an Intrazonal Trip

9. 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 9

10. Intra-Superzone Assignment Example
Aggregate OD Matrix
Intra-Superzone Trip
Inter-Superzone Trip
Correspondence Table
Disaggregate Intra-Superzone Trip

11. Zonal Aggregation Models
Superzone Connector Assignment
To better assign Inter-Superzone Trips
Should really be this
This Trip 11

12. 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 12

13. Demo of Sketch Plan Model13

14. Model Run Times Regional Model – 24 hours
Full Sketch Plan Run – 2 hours
One-loop highway-only run – 75 minutes 14

15. Calibration Results 15

16. Calibration Results 16

17. Future Work Explore Random allocation of zones for skimming
Add transit-only component
Integration with TDM and land use models
Additional optimization

18. Thank You