The GreenSTEP model was developed by the Oregon Department of Transportation to estimate and forecast the effects of policies and other influences (e.g. gas prices) on the amount of vehicle travel, the types of vehicles and fuels used, energy consumption for vehicle travel, and resulting greenhouse gas (GHG) emissions. The name, GreenSTEP, is an acronym which stands for Greenhouse gas Strategic Transportation Energy Planning. The full name of the model helps to describe the model's origin and function.
Greenhouse gas: The origins of GreenSTEP's development and its main applications have been for the purpose of estimating and forecasting greenhouse gas emissions from the transportation sector.
Strategic: GreenSTEP was designed to support strategic planning efforts which require the consideration of many possible scenarios and contingencies. It combines higher level analysis with an ability to compute the effects of a large variety of factors that influence vehicle ownership, use, energy consumption and greenhouse gas emissions. It runs rapidly so that many scenarios and contingencies can be analyzed in a reasonable amount of time.
Transportation: The initial focus of GreenSTEP was on household travel using light duty vehicles. This focus reflected a statutory emphasis on reducing emissions from this portion of the transportation sector. GreenSTEP's capabilities are being expanded over time to address household travel more completely and to address more portions of the transportation sector. For example, although walking does not produce any greenhouse gas emissions, a walk model was added because the amount of walking is an important indicator of the health effects of a transportation and land use scenario. Work is also underway to incorporate air travel into the household emissions estimates.
Energy: In addition to computing greenhouse gas emissions, the GreenSTEP model calculates the amount of fuel and electricity consumed for the transportation modes that it models. This enables GreenSTEP to be used to assess potential consequences for fuel consumption, electricity consumption, household fuel expenditures, gas tax receipts, and related effects.
Planning: GreenSTEP is a planning model that can be applied at the statewide level or metropolitan level. It is being used to provide analytical support for a number of planning purposes such as the development of Oregon's Statewide Transportation Strategy for reducing greenhouse gas emissions, the Climate Smart Communities Scenarios project for the Portland metropolitan area, the Oregon Governor's Ten Year Energy Action Plan, and the assessment of the future effects of hybrid, plug-in hybrid, and electric vehicles on fuel tax receipts.
GreenSTEP can be applied at different geographic scales. When the model is applied at the statewide scale, the geographic area is subdivided into counties and population is apportioned to the urbanized, other urban, and rural portions of each county. Similarly, when the model is applied at a metropolitan scale, the geographic area is subdivided into districts and population is apportioned to the urbanized, other urban, and rural portions of the district. However, metropolitan applications may be limited only to the urbanized portions of the metropolitan area. GreenSTEP can be scaled to different geographies because the model does its calculations at the household level. Individual households are simulated with regard to their characteristics.
GreenSTEP then simulates vehicle ownership and use, energy consumption, and greenhouse gas emissions for each household given the household's characteristics and other relevant factors such as fuel prices, land use, transportation services, and the penetration of advanced vehicles in the market.
The household level model results and other GreenSTEP calculations can be used to calculate a wide variety of travel, energy, greenhouse gas, economic, and health measures. Examples can be seen in the Statewide Transportation Strategy technical appendices. The large number of model outputs and capabilities for evaluating many scenarios can pose a challenge for making sense out of massive amounts of data. Data visualization methods are being developed to help with this task. GreenSTEP Scenario Viewer is an example.
The GreenSTEP model was reviewed extensively by state, national and international travel and emissions modeling experts in multiple venues. Evaluation at the national level lead to the Federal Highway Administration adopting GreenSTEP as the basis for their EERPAT model. In 2010, the American Association of State Highway and Transportation Officials (AASHTO) awarded ODOT staff its Presidents Award for Planning for the development of the GreenSTEP model. Following is documentation for the GreenSTEP model: