Travel Demand Model

Screenshot from SRTC’s Travel Demand Mode

Many of the transportation planning activities performed by SRTC require Travel Demand Modeling; a method of representing how people use the transportation system now and forecasting travel behavior in the future. Modeling uses computer software to analyze modes of travel including walking, biking, bus, personal vehicles and carpool. Modeling takes into consideration the demand on the transportation system and assists community leaders and partner agencies in making transportation investment decisions.

SRTC’s travel demand model contains inventories of existing transportation facilities and of all housing, shopping and employment in the area. Using the model, transportation planners can estimate future traffic volumes and transit ridership.

The model is used to evaluate transportation measures such as transit ridership, traffic volumes, miles traveled, travel speeds, and delay on the regional transportation system. The model’s land use data comes from a variety of sources: WA State Employment Security Department, Department of Revenue, Department of Health, Census, comprehensive plans, and building permits. Results from the travel demand model are often used for corridor studies, subarea plans, and air quality analysis.

SRTC uses a “4-step” model:

  1. Trip Generation (land-use & economic factors determine how many trips people will make)
  2. Trip Distribution (determines where trips start and end)
  3. Mode-choice (determination of how you get to your destination; e.g., bus, walk, drive, etc.)
  4. Trip Assignment (determination of which path you take from your trip origin to your trip destination)

Travel Forecasting Documentation
Federal transportation planning regulations require documentation of the input assumptions and methods used for developing travel forecasts [23 CFR 450.316]. The documentation of the 2013 MTP Update, Horizon 2040, includes an inventory of the current state of transportation in the planning area, key planning assumptions used in developing forecasts, and descriptions of the methods used to develop forecasts of future travel demand. The documentation and corresponding appendices are below. For Word document versions, please email contact.srtc@srtc.org or call (509) 343-6370.

Land Use Documentation and Planning Assumptions

In 2015, SRTC hosted a model peer review to receive feedback from national experts on the Spokane regional model compared to the state of the travel demand modeling practice. The objective of the peer review was to better understand the capabilities of the current model and how to proceed with model improvements. An overview of the peer review and the resulting recommendations are summarized in the SRTC Model Peer Review Report.

In 2018, Dr. Michael Clay evaluated SRTC’s methodology for projecting and allocating future employment and housing inventories to be used in SRTC’s model. Dr. Clay holds a PhD in Transportation Technology and Policy and specializes in assisting mid-sized MPOs in evaluating their current modeling methods. Dr. Clay delivered his results in a presentation that was recorded and posted here. 

Model Data
As a service to SRTC partner agencies and the consulting firms they work with, SRTC provides transportation modeling data in an effort to ensure regionally consistent transportation studies in Spokane County. That data can include transportation networks, operating characteristics, households and employment by transportation analysis zones, and modeling assumptions. This information is provided free of charge, although there may be minimal costs associated in reproducing this information.

In order to receive transportation modeling data, please fill out this Model Data Request Form updated and email it to contact.srtc@srtc.org.