Travel Demand Modeling


The Shasta Regional Transportation Agency (SRTA) develops and maintains the regional travel demand model, which forecasts land use and corresponding travel behavior at least 20 years into the future for the Shasta County region. It is an important tool used for a variety of planning and programming activities at the agency.  Through modeling SRTA can estimate future traffic volumes, identify potential congestion points, evaluate traffic impacts related to future development projects or policies, and calculate related vehicle emissions.  

Current Travel Model - Shasta County Regional Activity-based Travel Model (ShastaSIM)

ShastaSIM is an advanced activity-based tour model that simulates the travel behavior of all residents in Shasta County over the course of a typical 24-hour weekday. ShastaSIM represents these travel activities as a series of "trip-legs" or "tours" connecting activities each person engages in, such as going to work, shopping or attending school.  The county population is represented by a "synthetic population" which is based on socio-demographic data collected by the US Census.  General land use information (such as residential, office or commercial) is represented at the parcel-level.  This level of detail allows SRTA to evaluate how changes in local/regional/state policies, completion of infrastructure projects or demographic changes of the population (e.g. an aging population) may impact transportation on our highways and local roads, the transit system and/or land use in the region.

The current model version (ShastaSIM 1.2) was adopted on October 9, 2018.  The previous model (version 1.1) was adopted on June 30, 2015.

Policies regarding use of the regional model can be found here: SRTA Travel Demand Model Policies (PDF)

Request Form

To request a copy of the model or specific travel model data, please fill out our request form
  1. DaySIM Documentation
  2. ShastaSIM (v1.0) Docs
  3. ShastaSIM (v1.1) Docs
  4. RTP Model Support Docs