TPB News

Updates to 30-Year Transportation Plan and Growth Forecasts Bring Region's Future Into Clearer Focus

Jul 23, 2012

As it adopted updates to the region's 30-year transportation plan during its most recent meeting on July 18, the Transportation Planning Board at the same time made official new regional forecasts of population and job growth that were compiled by the Metropolitan Washington Council of Governments (COG) earlier this year. Together, the long-range plan and the new growth forecasts make it easier to see what the Washington region will look like in 2040 under current trajectories of planning and funding.

The new growth forecasts, referred to as Round 8.1 of COG's Cooperative Forecasts, were mainly an effort to adjust earlier forecasts to reflect updated population data collected during the 2010 Census. The previous round of forecasts -- Round 8.0 -- was adopted by COG and the TPB in November 2010 before the results of the decennial census were available.

In many cases, the counties, municipalities, and neighboring regions that provide independent forecasts of population and job growth as part of the regional forecasting effort had to revise their predictions of future growth upward or downward based on the new "starting point" provided by the census. About as many jurisdictions had previously overestimated the 2010 population as had underestimated it.

Some jurisdictions also made adjustments to their earlier forecasts of population and employment based on continued economic uncertainty, changes in the number of permits for new construction that have been granted since 2010, or changes to longer-term plans for future commercial or residential development.

As the regionally adopted forecasts of future growth, the Cooperative Forecasts are a key input into the TPB's annual Air Quality Conformity Analysis, which is a federally mandated process for determining whether total future vehicle-related emissions in the region will comply with federal standards.

To forecast future emissions, COG's population and job growth forecasts are used in conjunction with the TPB's plans for the future of the transportation system to predict where, when, and how often people will travel and whether they are likely to drive, take transit, or bike or walk to their destinations. Such analysis must be completed before the TPB can approve changes to the long-range plan.

The TPB also uses forecasts of future travel patterns to assess the degree to which the transportation system as it is currently planned will handle the demands that future population and job growth will create.

COG and the TPB coordinate the adoption of updates to the Cooperative Forecasts with adoption of updates to the region's constrained long-range plan (CLRP) because changes in population and job growth -- and changes in where that growth will occur -- affect and are affected by decisions about the future of the transportation system.

One example of why such coordination is important is the addition to the CLRP in 2004 of the Inter-County Connector (ICC) between Montgomery and Prince George's Counties in Maryland. Before the project could be added to the plan, forecasts of changes in population and employment patterns that were anticipated to occur as a result of the new highway had to be included in the TPB's 2004 Air Quality Conformity Analysis.

In 2000, COG also had to add new jobs and new residential units to the area near what is now the NoMa-Gallaudet U stop on Metrorail's Red Line before the TPB could add the station to the plan. The District of Columbia Office of Planning revised previous forecasts of population and job growth to reflect the changes in land-use that were anticipated to occur near the new station once it was constructed.

The most recent changes to the Metropolitan Washington Council of Governments' Cooperative Forecasts, while mostly technical in nature, reflect a continuing need to update land-use plans and transportation plans in a coordinated manner. These updates provide a realistic, up-to-date baseline of anticipated future conditions that planners, decision-makers, and the general public can use to assess the benefits of potential new land-use and transportation proposals in the Washington region.

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