Developing a Sketch Plan Model for the Southern California Association of Governments

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 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

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

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

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

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

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

13. Demo of Sketch Plan Model

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

15. Calibration Results

16. Calibration Results

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