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Step 4: Develop and Evaluate Base Year Conditions and a Reference Case

Step 4 Summary

View the full Scenario Planning Guidelines (PDF).

In this step, information about existing or recent conditions in the planning area are compiled to create a base year conditions report. Growth forecasts from existing plans are then added to the base year conditions to develop a "reference case" for the selected planning period. The base and reference case show both performance today and how well current plans are expected to perform in achieving various local objectives, including reducing GHG emissions, by the end of the planning period. The development and evaluation of the base year conditions and the reference case are useful for engaging decision-makers, advisory committees, and the public in discussions about potential strategies for the future, which would be tested later in the alternative scenarios.

Scenario planning starts with developing an understanding of current conditions, or "where the metropolitan area is today," and then evaluating the likely results of existing plans and policies in a reference case. Use of Metropolitan GreenSTEP (PDF) to perform an early high-level strategic assessment of conditions in the base year and the outcomes of the reference case is recommended before embarking on a more detailed analysis utilizing a sketch planning tool.

Base Year Conditions
Documenting base year conditions gives the decision-makers and the public a clear picture of current conditions and an assessment of whether things are likely to get better or worse in the future – either in the reference case or in the different alternative scenarios that are developed in the next step. Using the data and information collected in Step 3, a base year can be described and modeled in Metropolitan GreenSTEP, with the results providing a benchmark accounting of today’s transportation behavior and GHG emissions.
  • Oregon's metropolitan areas have a wealth of data available related to housing units, households, commercial uses, employment and existing transportation networks. These datasets form the backbone of defining the base year conditions.
  • Instructions for defining the base year conditions are explained in further detail in the Technical Appendix (PDF).
  • Results of the analysis will include the outputs of Metropolitan GreenSTEP, the sketch planning tool and any other models used.
Reference Case
The reference case is an estimate of where current adopted land use and transportation plans are likely to lead the metropolitan area over the selected long-term planning period.
  • The reference case developed with Metropolitan GreenSTEP will incorporates detailed assumptions about state and federal policies, and other local assumptions expected to be in place over the planning period as described in Step 3 and the Technical Appendix (PDF).
  • Metropolitan GreenSTEP accounts for the combined effect of all these factors to estimate a series of transportation related outcomes, including GHG emissions.
Baseline Assumptions
Baseline assumptions include assumptions about future conditions likely to affect people’s travel habits. These include estimates about the price of gasoline, forecasts about future vehicle technologies, and estimates about expected state and federal policies and programs, including state and federal funding for transportation.
Report Card
The process includes the use of evaluation measures (identified in Step 2) that indicate how well the metropolitan area is doing – and is expected to do in the future – in terms of such things as housing affordability, jobs-to-housing balance, amount of open space, and GHG reduction. This information is presented to the community as a report card. This report card provides an opportunity to engage stakeholders in a discussion about where the community is heading based on current trends, and identify key issues or problems that the community may want to explore further.

Three-Part Approach to Assembling Materials for Use in Discussions with Board or Advisory Group or a Full Public Engagement Process (PDF).