Travel Demand Model
The Travel Demand Model analyzes how people use the regional transportation system and forecasts future travel behavior. The model is used by transportation planners to estimate future traffic volumes and transit ridership and aid in a variety of transportation plans, studies and analyses. Additionally, transportation planners use the model’s evaluations to make important investment decisions. The Travel Demand Model also analyzes other modes of travel besides transit such as walking, biking, personal vehicles and carpooling.
What is the 4-Step Model?
A travel demand model is a software tool that uses mathematical equations to estimate future travel. SRTC uses a traditional trip-based model with four major steps: trip generation, trip distribution, mode choice, and trip assignment.
Trip Generation:
Land-use and economic factors determine how many trips people will take.
Trip Distribution:
Determines where trips start and end.
Mode Choice:
Determines how you get to your destination such as the bus, walking, driving, etc.
Trip Assignment:
Determination of which route 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. The Metropolitan Transportation Plan, Horizon 2045, includes an inventory of transportation systems and services in the region, key planning assumptions used in developing forecasts, and descriptions of the methods used to develop forecasts of future travel demand. In 2024, SRTC released a new 2022 base model and 2050 forecast model. Links to the planning assumptions and model documentation are below.
Access to Model Data
SRTC provides transportation modeling data to partner agencies and their consulting firms to ensure regionally consistent transportation studies in Spokane County. This information is provided free of charge unless reproducing the requested information has associated costs.
The data includes:
- Transportation networks
- Operating characteristics
- Households and employment data organized by transportation analysis zone
- Modeling assumptions
