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Activity Based Model

SANDAG has completed the transition from an enhanced four-steptransportation model to an activity based model (ABM). An ABM simulates individual and household transportation decisions that compose their daily travel itinerary.

SANDAG Activity Based Model

ABM2+ (2021 Regional Plan, Series 14 Land Use)

SANDAG completed the transition from an enhanced four-step transportation model to an activity-based model (ABM1) in 2013 and applied ABM1 in the 2015 Regional Plan. SANDAG has since completed the development of ABM2 and applied it in the 2019 Federal Regional Transportation Plan. SANDAG is currently utilizing ABM2+ to support the 2021 Regional Plan, also known as the 5 Big Moves.

The SANDAG ABM includes a number of methodological strengths. It predicts the travel decisions of San Diego residents at a detailed level, taking into account the way people schedule their day, their behavioral patterns, and the need to cooperate with other household members. When simulating a person's travel patterns, the ABM takes into consideration a multitude of personal and household attributes like age, income, gender, and employment status. The model's fine temporal and spatial resolution ensures that it is able to capture subtle aspects of travel behavior. The SANDAG ABM strives to be as behaviorally realistic as possible and is based on empirical data collected by SANDAG, Caltrans, and the federal government. The model development has been regularly peer-reviewed by the ABM Technical Advisory Committee, a panel of national experts in the travel demand forecasting field.

ABM2+ Documentation

  • SANDAG Emme User Guide: ABM2+ is run using the transportation planning software Emme. This document provides an overview of the implemented modeling framework as well as a "how-to" for running the model.
  • SANDAG ABM2+ Base Year Validation Report: Interactive data visualizations that show how ABM2+ model results are validated against empirical data.
  • SANDAG ABM2+ Sensitivity Report: Contains sensitivity tests that describe the modeled effects of various inputs on metrics such as VMT, mode share, trip length, and transit boardings using ABM2+.
  • GitHub: GitHub is a repository used by many organizations and companies to store and keep track of edits to code for projects. SANDAG uses GitHub to keep changes to the ABM transparent to the public. More reports and documents for ABM2+ can be found here.

ABM2 (2019 Federal Regional Transportation Plan, Series 14 Land Use)

SANDAG ABM2 utilizes the 2016-2017 Household Travel Survey (HHTS) and the 2015 Transit On Board Survey (OBS) data to calibrate and validate the existing ABM1 and updated model (ABM2) for the development of the 2019 Federal Regional Transportation Plan. In the long term, SANDAG will re-estimate the ABM2 based on 2016 HHTS and 2015 OBS data and use the updated model for the 2023 Regional Plan.

ABM2 Documentation

Improvements to ABM2 since ABM1

Since the first release of ABM used in the 2015 Regional Plan, SANDAG has made numerous improvements and upgrades to the ABM. A few noteworthy efforts are listed below:

  • Travel Behaviors from 2015 Transit On Board Survey and 2016-17 Household Travel Behavior Survey
  • Increased travel time reliability
  • Escort model for dropping off/picking up to and from school
  • Tour-based Commercial Travel Model (CTM)
  • Cross Border Xpress (CBX) air passenger model
  • Updated heavy truck model
  • Improved transit path finding procedure
  • Migration from TransCAD to Emme

ABM1 Documentation

Current Improvements and Upgrades

SANDAG is currently working on the next generation of ABM. ABM2+ to be used in the 2021 Regional Plan will be an update to ABM2 and include recent technologies such as Transportation Network Companies (TNCs), micromobility, and future connected and autonomous vehicles.

More Information

  • ABM2+ Wiki: The ABM2+ Wiki serves as a user guide to describe the structure of the model, its setup and running procedures, and its inputs and outputs. It also includes reports and documents of model updates, enhancements, and sensitivity tests.
  • GitHub

Next Generation


ActivitySim is an open platform for activity-based travel modeling. It emerged from a consortium of Metropolitan Planning Organizations (MPOs) and other transportation planning agencies that wanted to build a shared, open, platform that could be easily adapted to their individual needs, but would share a robust, efficient, and well-maintained common core. Some of the advantages of ActivitySim include that it is distributed to the public at no charge and that all member agencies help make decisions about development priorities. As a result, each member benefits from the contributions of other members.


VisionEval is a programming framework for performance-based transportation planning. State and metropolitan-area governments address transportation issues via the strategic tools used by transportation modelers. Because VisionEval provides an open-source and common framework, it allows new model features to be added and shared easily among models.

Travel Model Improvement Portal - Exploratory Modeling and Analysis Tool (TMIP-EMAT)

TMIP-EMAT provides a methodological approach to exploratory transportation modeling and analysis. It includes rigorous methods for handling uncertainty and making informed decisions for all travel forecasting models. Additionally, TMIP-EMAT is designed to integrate into an existing model/tool to perform exploratory analysis over a wide range of scenarios.