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FAQs
1. How many ABM versions does SANDAG maintain?
There are two released ABM versions, ABM1 and ABM2. ABM1 was released in January 2013. An updated version of ABM1 was used in “San Diego Forward: The Regional Plan,” adopted by the SANDAG Board of Directors in October 2015. ABM2 was released in June 2019 and was used in the SANDAG 2019 Federal Regional Transportation Plan adopted by SANDAG Board of Directors in October 2019. SANDAG is currently working on updating ABM2 to ABM2+ for applications in the San Diego Forward: The 2021 Regional Plan (2021 Regional Plan).
2. What is ABM2+ for? What’s the difference between ABM2 and ABM2+?
The ABM2+ is designed for application in the 2021 Regional Plan, a bold new vision for the San Diego region that provides compelling alternatives to driving. The ABM2+ is built on top of ABM2 with enhancements to consider emerging technologies, including autonomous vehicles, shared mobility, ridehailing, transformative modes, and micromobility.
3. Who uses the SANDAG ABM and what for?
The SANDAG ABM is used by SANDAG and many other public and private entities in the San Diego region. These entities include the City of San Diego and other local jurisdictions, Caltrans District 11, San Diego Metropolitan Transit System, North County Transit District, and private developers. Typical ABM applications include analysis for regional planning, air quality conformity, corridor studies, and land use development impact studies.
4. What is the “flavor” of the SANDAG ABM?
The SANDAG ABM is based on the Coordinated Travel Regional Activity-Based Modeling Platform (CT RAMP) family of Activity-Based Models.
5. What model components does the SANDAG ABM have?
The SANDAG ABM is a suite of models covering various travel demand markets in the San Diego region. The microsimulation model components include a San Diego resident model, a commercial vehicle model, a Mexican resident crossborder model, a visitor model, a San Diego International Airport ground access model, a Cross-Border Express model serving Tijuana International Airport, and a special event model. The aggregate model components include an external heavy truck model and external trip models.
6. What is the base year of the SANDAG ABM?
ABM1 has a base year of 2012. Both ABM2 and ABM2+ have a base year of 2016.
7. How many TAZs does SANDAG have? What are MGRAs?
There are 4,996 Transportation Analysis Zones (TAZs), including 12 cordon zones at the County border. The Master Geographic Reference Area (MGRA) is the SANDAG micro-analysis zone (MAZ) system. There are 23,002 MGRAs.
8. What Synthetic Population software does SANDAG use?
The Synthetic Population used in ABM2 and ABM2+ was developed by the SANDAG Economic and Demographic Analysis and Modeling group (EDAM). It combines a microsimulation of personal and household demographic evolution with elements of probabilistic imputation of socioeconomic attributes. The software is implemented in SAS.
9. What year of dollars are used for income and other costs in the SANDAG ABM?
2010 dollars.
10. What is the Active Transportation Model in the ABM?
The Active Transportation (AT) Model is an enhancement made to the original ABM1. The AT Model is designed to make the model system sensitive to bicycle infrastructure improvements such as the implementation of bicycle paths, lanes, and routes. In addition, the model system was enhanced to provide more accurate “all streets”-based measures of pedestrian accessibility.
11. How is travel time reliability modeled in the ABM?
In ABM2, SANDAG incorporated and implemented Strategic Highway Research Program recommendations regarding improving the sensitivity of travel models to pricing and reliability.
12. What programming languages are used to build the SANDAG ABM?
The disaggregate simulation models are implemented in Java. The aggregate models are implemented in EMME/Python. Microsoft SQL Server–based processes are used to load model results into a database and generate performance metrics.
13. What is the approximate model runtime?
The model runtimes vary by model year, scenario, and the server used. Approximate model runtimes in ABM2 recent release 14.1.0 for years 2016 and 2035 are 35 and 40 hours respectively. The model runtime in ABM 2+ release 14.2.1 for years 2016 and 2035 are 34 and 37 hours respectively, which was approximate 2~3 hours shorter than previous ABM2 releases. These runtimes are based on a single machine deployment.
14. How many ABM servers does SANDAG have? What are the specs?
SANDAG has 20 ABM servers. Typical specs of an ABM server are: Make Model OS Processor Physical Cores Logical Cores RAM Hard Drive Dell Server PER430 Windows Server 2012 R2 Std 2 Intel® Xeon® Processor E5-2690 v4 @2.60GHz 28 56 256GB 927GB
15. Is the ABM connected to a database?
Yes. Upon successful completion of an ABM model run, a batch file is executed as part of the model flow. This command inserts a record into the load request table indicating the run has successfully completed and provides all necessary information for the Extract-Transform-Load data pipeline to load the model run into the database. Each night, the load request table is checked for records, and any requested ABM model runs present in the table are loaded into the database.
16. Is a Cloud model available for the SANDAG ABM?
Test implementations of ABM1 have been deployed at the UC San Diego super-computing center. There are no current cloud implementations, but this is a possibility in the future.
17. Does SANDAG have a Dynamic Traffic Assignment model? Is it integrated with the ABM?
SANDAG, with WSP and Aimsun, created a regional 24-hour Dynamic Traffic Assignment (DTA) model using a Dynamic User Equilibrium simulation. The model uses the SANDAG ABM1 trip list and networks and signal timings from 2013–2015. The DTA model is not fully integrated with the SANDAG ABM and is currently only in use for research and development purposes.
18. What is the SANDAG Service Bureau? How is the ABM used in Service Bureau projects?
The SANDAG Service Bureau is the preferred source for customized demographic and economic studies, data and analysis, Geographic Information Systems analysis and mapping, and transportation modeling. Consulting services are available to government agencies and private businesses on a fee-for-service basis. Service Bureau staff deploy the ABM in support of Member Agencies General/Community Plan update process, in support of other government agencies special studies, and for analysis of land use developments proposed by the private sector.
19. What is the next version of the SANDAG ABM?
The next version is ABM3, and development work is set to start in October 2020. As part of ABM3 development, components will include re-estimating resident and special market models using recent survey data, further improving emerging technology model capabilities and model runtime, and exploring the possibility of transitioning from CT-RAMP Java software to ActivitySim. The ABM3, designed for the SANDAG 2025 Regional Plan, will be calibrated and validated to an updated base year yet to be decided.
20. What is the crossborder model? Any updates on the crossborder model?
The cross border travel model (CBTM) is a key ABM component that measures the impact of Mexican residents traveling on the San Diego transport networks and predicts border crossings at each port of entry. The existing CBTM used data from the 2010 travel behavior survey on Mexican residents who made border crossings into the United States. SANDAG is currently conducting 2019 Mexican resident cross border survey and will utilize the collected data to update CBTM to reflect border crossing travel behavioral changes since 2010. The CBTM is the first model component in the SANDAG modeling suite that will transition from Java-Based CT-RAMP to Python-Based ActivitySim.