Activity Based Model

Activity Based Model Thumbnail Image
Primary Purpose

The Activity-Based Model (ABM) is a new generation of travel demand model. According to the 2010 RTP Guideline by California Transportation Commission, the largest four MPOs in California are encouraged to transition to activity-based travel demand models for the following RTP cycle (if the model is not already developed and validated for the current RTP cycle). This new modeling system is designed to meet/exceed federal regulations and state laws and requirements.


SCAG’s ABM adopts a true activity-based approach by focusing explicitly on activity episode generation and their characteristics. Key model characteristics include:

  • ABM creates rich socio-economic characteristics for each person and for each household in the SCAG region;

  • Simulates daily activities and travel patterns of all individuals in the region, as affected by transportation system level of services;

  • Predicts decisions “whether, when, where, for how long, with whom and in what sequence” to participate in activities;

  • Simulates the effects of transportation and land development investments and policies on the quality (time and cost) and quantity (traffic volume, congestion, and vehicle miles traveled) of travel by different modes (walk, bike, transit, and auto); and

  • Generates performance indicators, conformity analysis, and environmental justice analysis for the 2016 RTP/SCS. It is being developed to be capable of analyzing the impact of infrastructure investment, land use development, pricing policy, active transportation, high speed rail, and travel demand management.


SCAG’s ABM incorporates a state-of-the-art approach to forecast travel behavior in a micro-simulation framework. Major strengths of SCAG ABM include: comprehensively characterizes the activity-travel patterns of all household members; incorporates spatial-temporal dependencies and constraints between and within individuals of a household; incorporates advanced vehicle type choice sub-model (vehicle fleet composition defined by body type, fuel type, make/model, and vintage) for emissions analysis; temporal and spatial resolutions; and involves a portable and flexible object-oriented software architecture design.


SimAGENT (Simulator of Activities, Greenhouse Emissions, Networks, and Travel) is the base framework of SCAG’s ABM. It includes three core modules:

  • PopGen – Generates complete synthetic population by expanding the disaggregate sample data to mirror known aggregate distributions of household and person variables of interest;

  • CEMSELTS – Creates additional variables for each individual and simulates long-term choices; and

  • CEMDAP - Simulates activity schedule and travel characteristics for each individual of the region.

Documents & Resources

Flow Chart Sequence of SimAGENT Modules and their interactions

Modeling Task Force Presentation: SCAG Activity-Based Model Development Workshop Presentation

Stage 1 Model Development Reports

SimAGENT Final Report 1 - Overview
SimAGENT Final Report 2 - Opportunity-Based Dynamic Accessibility Indicators in SimAGENT
SimAGENT Final Report 3 - Population Synthesis
SimAGENT Final Report 4 - Activity-Based Travel Demand Analysis
SimAGENT Final Report 5 - TRANSIMS and MATSIM Experiments in SimAGENT

SimAGENT Research Papers

A Joint Vehicle Holdings (Type and Vintage) and Primary Driver Assignment Model with an Application for California
A Methodology to Match Distributions of Both Household and Person Attributes in the Generation of Synthetic Populations
A Household-Level Activity Pattern Generation Model for the SimAGENT System in Southern California
Simulator of Activities, Greenhouse Emissions, Networks, and Travel (SimAGENT) in Southern California
The Application of a Socio-Economic Model System for Activity-Based Modeling: Experience from Southern California

SCAG DTA Model Development & Training