GreenSTEP was the first of these models to be developed, and was designed by the Oregon Department of Transportation (ODOT) to assist in the development of plans to reduce greenhouse gas (GHG) emissions from light-duty vehicles to meet statutory goals. GreenSTEP models the consequences of changes in many different factors (such as transportation supply, prices, and land use) on household vehicle ownership and use, and the resulting effects on emissions, traffic congestion, and other outcomes. It’s strength is in the ability to incorporate significant detail through modeling a synthetic set of individual households and associated vehicles and fuels, incorporating a budget model for pricing policies, while avoiding network details that lead to long run times. GreenSTEP, a statewide model with county and metro area “zones”, has been used to establish long-range goals and identify the possible strategies to achieve these goals, such as reducing transportation related emissions by a certain percent, or ensuring that a certain percent of households live in walkable neighborhoods.
The design concepts in GreenSTEP are the cornerstone of the related models. As a strategic planning model, GreenSTEP sits between sketch planning models that operate using simplified rule-based methods use, and modeling each individual’s daily trips by purpose on a detailed network with interacting policies. . GreenSTEP and the other VisionEval models simulate individual households and interactions between policies, but forecasts only overall travel based on metropolitan-wide travel conditions rather than detailed networks, striking a balance between rapid computation of alternative scenarios and accurate representations of how different types of households will change travel behavior in response to policies and investments. These models allow rapid analysis of how actions may interact, such as how urban area density may interact with electric vehicle ownership or car sharing. They can also test how household behavior may respond to policy changes, for instance how VMT may change in response to future increases in fuel cost or tighter budgets during stagnant economic times.
The inputs to GreenSTEP are similar to what is required for the other VisionEval models. These can be summarized into household characteristics (age mix, household size, personal income, dwelling type), vehicle characteristics (fuel economy, vehicle age, powertrain type), and place characteristics (density, amount of transit service, mixed use development). Given these attributes, the model estimates outputs such as household travel, travel costs, emissions, and road congestion and environmental impacts.
GreenSTEP continues to be used as a State-wide planning tool by ODOT, but is not available on a public repository currently. The FHWA maintains the similar statewide Energy and Emissions Reduction Policy Analysis Tool (EERPAT) model. EERPAT has just made a significant enhancement to add a freight model and associated policies built on FHWA Freight Analysis Framework commodity flow data.
The models developed for GreenSTEP form the core of all VisionEval models. Following the successful transfer of RSPM and RPAT to the VisionEval project, Oreon DOT (and Maryland DOT) are leading the transfer of statewide GreenSTEP to VisionEval, via a contract led by CH2M Hill with sub-consultants RSG, Inc. and the original GreenSTEP author of Oregon Systems Analytics. A VEGreenSTEP model should greatly facilitate transferring EERPAT to VisionEval.