TPB News

Here's how we use growth forecasts for transportation planning

Mar 5, 2018
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(Fort Belvoir Community Hospital/Flickr)

Before the TPB approves its new long-range transportation plan, Visualize 2045, staff will complete two analyses. One will test the financially constrained element for its effect on the region’s air quality and the second will quantify forecasted changes in the transportation system.

These analyses will rely on recent updates to regional population, households and employment growth forecasts. The Metropolitan Washington Council of Governments (COG) coordinates the development of the forecasts, which are prepared by the local planning departments of its member jurisdictions.

A slight adjustment

This update—the Round 9.1 Cooperative Forecasts—shows how much growth is expected in the region between 2015 and 2045 as well as where that growth is expected to occur. Round 9.1 is an incremental update to Round 9.0, which was adopted by COG and the TPB in 2016. Drawing from existing or anticipated residential and commercial construction permits and local comprehensive plans, the latest update incorporates changes to land use and transportation. Overall, Round 9.1 shows a slight change of less than one percent when compared to Round 9.0. While regionally the change is small, it is considerable within specific areas of the member jurisdictions.

 


The Round 9.1 forecast shows how much growth is expected in the region between 2015 and 2045 as well as where that growth is expected to occur. Round 9.1 is an incremental update to Round 9.0, which was adopted by COG and the TPB in 2016. The graph shows the forecast for the number of households in the region to 2045. (COG)

 


This chart shows the forecast for the number of new jobs in the region to 2045. (COG)

Changes in these land-use based Forecasts reflect local comprehensive plans and economic development goals, as well as new transportation investments. The chart below shows examples of five regionally significant transportation investments that influenced these jurisdictions’ land-use Forecasts during the past 18 years.


Here are five examples of regionally significant transportation investments that influenced these jurisdictions’ land-use Forecasts during the past 18 years. (COG)

In Fairfax County a notable change is a plan for a major Bus Rapid Transit line along U.S. 1, Embark Richmond Highway. Fairfax County submitted forecasted changes in population and employment in the corridor along the route.

Land use and the 7 priority initiatives for Visualize 2045

Also new for Visualize 2045, TPB will examine how regional growth patterns may support the seven priority initiatives developed by the TPB’s Long-Range Plan Task Force. One of those initiatives is to focus on balancing and optimizing land use across the region. Specifically, it recommends that the region aspire to have more households overall in the future, and to increase housing and employment in Activity Centers —places where people can live, work, and play—and near high-capacity transit. As called for in Region Forward, planners and policy-makers have always looked at the share of projected growth in Activity Centers, the new TPB initiative calls for doing more of this to reduce congestion and increase mobility options in the future.

In the graph below, Round 9.1 shows that three-fourths of all new jobs are expected to be in Activity Centers. In addition, 64 percent of new household growth is also expected to occur in Activity Centers. The forecasts can provide information for regional leaders to explore ways to bring more homes closer to employment centers or bring jobs closer to where people live.


These graphs illustrate the forecast for growth in jobs and households in Activity Centers. These are hubs where people live, work, and play. (COG) 

Travel patterns and emissions

To forecast future vehicle-related emissions, the TPB will analyze changes in travel patterns anticipated over the next 25 years brought about by land use changes contained in the Cooperative Forecasts. The emissions forecasts also consider how new vehicle technologies, more efficient energy systems, and cleaner-burning fuels, are expected to evolve, and how quickly those changes are expected to occur.

In developing Visualize 2045, the region must demonstrate through the Air Quality Conformity Analysis that future emissions from the projects and programs in the financially constrained element collectively will remain below regional limits known as "emissions budgets."

Both the performance analysis and the Air Quality Conformity Analysis are meant to provide decision-makers and the public with information about how well planned and funded transportation investments will meet the region's future transportation needs.

The air quality analysis continues through the spring and summer as part of Visualize 2045. Then staff will analyze the transportation system’s performance. Once completed, the analyses will be available for review by the TPB, its stakeholders, and the public for 30 days before the TPB votes to approve Visualize 2045 at its October meeting.

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