The Transportation Agency uses the regional model for a variety of planning activities, and a realistic representation of travel behavior is critical to developing solutions for priority safety and congestion projects.
For the 2018 Metropolitan Transportation Plan / Sustainable Communities Strategy, the Association of Monterey Bay Area Governments completed an update to the Regional Travel Demand Model. The current model includes detailed transportation and transit networks, as well as a geographically based Traffic Analysis Zone layers (similar to census blocks) containing socioeconomic data for the base year 2015 and forecast year 2040. The model has a base year of 2015, established using data from the 2010-2012 California Household Travel Survey, United States Census, employment, and traffic counts.
This current model is a traditional four-step model, which begins with a forecast of land use. Forecasts are made for the region as a whole of population growth, then the region is divided into zones by trend or regression analysis, and the population and employment are determined for each. The model uses this information in the following four-steps to develop the travel demand forecast:
- Trip generation determines the frequency of origins and destinations of trips in each zone by trip purpose;
- Trip distribution then matches origins with destinations;
- Mode choice attributes the proportion of trips between each origin and destination that uses a particular transportation mode (the current AMBAG model can only provide a percentage of mode split for non-vehicle modes); and
- Route assignment allocates trips between an origin and destination by a particular mode to a route (the current model assigns routes based on available capacity and shortest travel time).
In collaboration with San Luis Obispo Council of Governments, and Santa Barbara County Association of Governments, AMBAG applied for and was awarded a Caltrans Planning Grant to develop the Central Coast Supra-Regional Activity-Based Model Framework. Under this project, the team is developing an advanced activity-based modeling framework for over 30 jurisdictions in California's Central Coast region. Activity-based models represent the state-of-the-art in travel demand modeling and offer a more accurate modeling paradigm over the traditional four-step models, largely because they track travel behavior at an individual level rather than aggregating trips into groups.
The project will involve the analysis of recent travel behavior survey data to develop, calibrate, validate and forecast passenger travel using daily simulated activity patterns. The activity-based model framework will then replace the existing four-step regional travel demand models throughout the region during the development of each Metropolitan Planning Organization’s next Regional/Metropolitan Transportation Plan and associated Sustainable Communities Strategy. The final activity-based model framework will help each agency evaluate transportation policies and system performance.
Bhupendra Patel, Director of Modeling for AMBAG, will provide a presentation to the Technical Advisory Committee on the model update project.