SANDAG ABM3

Welcome to the SANDAG Activity-Based Travel Model documentation site!

Introduction

This website describes the travel demand modeling system developed by the San Diego Association of Governments (SANDAG). SANDAG plans for many complex mobility issues facing the San Diego region, including development of the Regional Plan. Transportation models are complex analysis tools used to provide transportation planners and policymakers with information to help allocate scarce resources fairly and equitably. As we plan for the future, models are used to forecast potential future scenarios of where people will live and how they will travel. They are the principal tool used for alternatives analysis.

The SANDAG transportation model is an activity-based model (ABM). It simulates individual and household transportation decisions that make up their daily travel. This includes all trips people make on a daily basis, such as to work, school, shopping, healthcare, and recreation. An ABM provides a controlled, analytical platform so that different inputs and alternatives can be evaluated to predict whether, when, and how this travel occurs. SANDAG ABM accounts for a variety of different weekday travel markets in the region, including San Diego region resident travel, travel by Mexico residents and other travelers crossing San Diego County’s borders, visitor travel, airport passengers at both the San Diego International Airport and the Cross Border Xpress bridge to the Tijuana International Airport, and commercial travel.

The most recent version of the SANDAG ABM is referred to as “ABM3”, and was developed for use in the 2025 Regional Plan. ABM3 is a significant enhancement from ABM2+ which was used for the 2021 Regional Plan. All of the passenger demand models in ABM2+ were converted from CT-RAMP to ActivitySim, including resident travel, cross-border travel, visitor travel, and airport travel. The internal-external travel component is now fully integrated with the resident model. The model was also enhanced to improve the representation of household and person-based mobility, vehicle fleet ownership, transit, shared and private micro-mobility, and micro-transit. Many of the model components were re-estimated using household survey data collected in 2022, and all model components were re-calibrated to base-year 2023 conditions. A new disaggregate commercial vehicle model was developed based upon a 2020 commercial vehicle survey, and implemented in ActivitySim.

This website includes a description of the model system, how to set up and run the models, and a description of model inputs and outputs. Some aspects of the site are a work-in-progress, so we recommend that you check in often, and share your thoughts on ways to improve the site with SANDAG Transportation Modeling staff. Thank you!