Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home
Public Roads
Featuring developments in Federal highway policies, programs, and research and technology.
This magazine is an archived publication and may contain dated technical, contact, and link information.
Federal Highway Administration > Publications > Public Roads > Vol. 77 · No. 2 > Predicting the Future?

September/October 2013
Vol. 77 · No. 2

Publication Number: FHWA-HRT-13-006

Predicting the Future?

by Lew Villotti and W. Kirk Brethauer

A Pennsylvania MPO takes the mystery out of scenario planning and the growth projections used by transportation agencies.

Communities in southwestern Pennsylvania used the scenario planning process to develop a vision scenario that prioritizes investments in revitalization and redevelopment of existing infrastructure, including central business districts like this one in Beaver, PA.
Communities in southwestern Pennsylvania used the scenario planning process to develop a vision scenario that prioritizes investments in revitalization and redevelopment of existing infrastructure, including central business districts like this one in Beaver, PA.

Who can predict the future? Whether designing an improvement to an intersection, identifying potential transit routes, or developing freight corridors, planners need to forecast the future. Although sometimes predictions such as these may resemble more art than science, they really are a bit of both.

Base data can help determine the needed capacity of the intersection, headways (times between bus or train arrivals) for the transit route, or the future need for freight movement in the corridor--all to ensure that the facilities have the ability to serve the public’s needs down the road. When looking forward, designers of these facilities need to predict the future number of vehicles, the potential ridership, or the number of freight containers.

How fast will the surrounding area grow? What types of growth will occur? What steps do planners take to estimate future needs? Here is where scenario planning can play an important role.

Scenario Planning

In the early years of developing growth projections, they were almost purely developed using straight-lined trending. That process involves simply carrying the most recent past trends from the current situation to some point in the future, using an annual growth factor. Although accurate in the near term, the overall usefulness of this approach over time was dependent on duration and stagnation. The farther from the origination date, the less accurate the projections became, because the important input variables changed, instead of staying stagnant, and their ability to maintain accuracy degraded.

Modelers compensate for this problem by developing more reactive policy models that allow for policy changes, thereby altering the outcomes computed by the models. In recent years, as the use of policy models gradually became more commonplace and the models became better able to capture changes in policy, the use of scenario planning in regional transportation planning also began to take hold. As the policy models became more sophisticated, they became able to distinguish the outcomes of different future scenarios.

This aerial photograph shows Southside Works, a redevelopment of a former brownfield site in Pittsburgh, PA. Brownfield redevelopment is one of the key regional policies that came from an MPO’s scenario planning for southwestern Pennsylvania.
This aerial photograph shows Southside Works, a redevelopment of a former brownfield site in Pittsburgh, PA. Brownfield redevelopment is one of the key regional policies that came from an MPO’s scenario planning for southwestern Pennsylvania.

A scenario is essentially a story about the future that helps people understand the forces of change and the collective choices they have. Scenarios show alternative futures by using maps, pictures, and text that illustrate different projections of future conditions that could occur as a result of varying policy choices. By associating diverse policies with different scenarios, a planner can visualize anticipated outcomes of future alternatives so that policymakers and the public can react in the present.

Scenario planning integrates policy models with geographic information systems (GIS) to form a powerful tool. It not only helps decisionmakers evaluate alternate policies but also assists planners in predicting future conditions and growth by connecting policies to future land use patterns. Before adding GIS, policy models could show numbers only. With the geographic element added, the models could depict variant land uses.

As Fred Bowers, a transportation planner with the Federal Highway Administration’s (FHWA) Office of Planning, Environment & Real Estate, states, “FHWA considers scenario planning an enhancement to, not a replacement for, the traditional planning process. We are committed to advancing scenario planning through workshops, webinars, and research. We support other Federal, State, and local agencies in their scenario planning efforts, and we will continue to help communities solve problems through scenario planning workshops tailored to meet their needs.”

At the forefront of forecasting through the use of scenario planning are metropolitan planning organizations (MPOs).

Who Does It

When the U.S. Congress passed the Federal-Aid Highway Act of 1962, the new law required the formation of an MPO for any urbanized area with a population greater than 50,000. In a metropolitan area with more than 50,000 people, the responsibility for transportation planning lies with the MPO designated for that city.

As the organizations responsible for planning metropolitan transportation, MPOs examine travel patterns in their regions and couple that analysis with a review of demographic and economic conditions to identify transportation issues and needs within their jurisdictions. This long-range planning includes an analysis of alternatives to meet projected future demands, while providing a safe and efficient transportation system to ensure mobility without creating adverse impacts on the environment. For many MPOs, this planning process includes the development of forecasts and growth projections for population, housing, and employment.

Diagram. This diagram is divided into two halves. On the left side are three sets of icons that serve as a legend for the other side of the diagram. The first set of icons, under the heading Primary Development Density, has two circles containing dots of various sizes. The first circle is labeled “High Density” and has a large number of dots; the second circle is labeled “Medium Density” and has fewer dots. Next down is a set of icons under the heading Primary Development Mix, with two ovals—one labeled “Low Separation” and containing building icons crowded together so they are touching, and the other labeled “Moderate Separation” and containing building icons spaced apart so they are not touching. Underneath that set of icons is the final set, under the heading Primary Transportation Elements, with a bus icon representing “Mass Transit,” a stick figure and a bicycle icon representing “Pedestrian/Bike,” and a railroad tracks icon representing “Rail.” On the right side of the diagram is the “Compact Sketch Scenario,” where icons for trees, buildings spaced apart (moderate density development), buses (transit), stick figures (pedestrians), and railroad tracks (rail) are all close together but not touching and therefore representing the Compact/Infill/Transit-Oriented Scenario—a future where investments would be made around existing older communities with transit as the primary transportation mode.
This sample sketch scenario for southwestern Pennsylvania depicts the density and mix of development and transportation system elements associated with a compact development scenario.

Federal- and State-mandated programs use regional and subregional socioeconomic estimates and projections developed by modelers to support long-range transportation plans and shorter range transportation improvement programs. In addition, modelers use the forecasts for other critical aspects of the planning process, such as air quality modeling, land use plans, and environmental justice analyses. Aside from the planning process, MPOs and transportation agencies often use the growth projections in project-specific planning, design, and evaluation; program design and evaluation; and program implementation. Integrating growth projections with scenario planning enhances all of these efforts.

Richard J. Hoch, Ph.D., AICP CEP and assistant professor in the Department of Geography and Regional Planning at Indiana University of Pennsylvania, considers scenario planning to play a critical role in the planning process. “Developing land use plans or environmental impact assessments requires the use of scenario planning,” he says. “Scenario planning legitimizes the process in a way that is acceptable to professionals and understood by the public.”

Case Study in Scenario Planning

In the summer of 2007, the MPO for the 10-county metropolitan region surrounding Pittsburgh, PA--the Southwestern Pennsylvania Commission (SPC)--adopted a transportation and development plan that was the culmination of a scenario planning process known as Project Region. Reviewing the history of this process provides an illustration of how scenario planning is done.

SPC’s Project Region involved a set of organized activities to help the 10 counties of southwestern Pennsylvania work together to develop a regional consensus on a growth plan. To achieve this consensus and the most effective strategies for the future, Project Region used analytical tools, community involvement, and scenario development. The SPC members designed the Project Region process to maximize regional assets and infrastructure to achieve balanced, cost-effective growth; capitalize on investments in existing communities; and strengthen quality job creation and regional economic competitiveness.

Diagram. Labeled “Places Policies,” this vertical “ladder” graphic is labeled “Tally Score” on the vertical axis, with horizontal lines drawn at scores of 20, 40, 60, 80, 100, and 120. To the right of the ladder is a legend. The first symbol in the legend is a green diamond that represents the policy statement, “Revitalize & redevelop existing communities,” which received a score of about 110 on the value ladder. The next symbol, a red square representing “Optimize investment at corridor level,” received a score of about 100. The third symbol, a blue triangle representing “Identify & develop industrial sites,” received a score of about 85 or 90. The final symbol, an orange X representing “Diverse development by type & location,” received a score of about 50.
In its scenario planning, SPC used value ladders to show the policy statements that the participants in the planning process considered most important or of greatest value to the region. Shown is the value ladder for policy statements on places.

The SPC members relied on FHWA throughout the planning process. The members started by reviewing past State, regional, and local plans to identify recurring themes and perspectives. They sought to develop a set of core common themes as the basis for initial policy statements. By developing these common themes through information provided in past plans, SPC was able to demonstrate that these policy statements had a direct lineage to past public feedback.

Through this process, the SPC members prepared close to 40 draft policy statements. An example is “Encourage the redevelopment of brownfields.” The members further refined these statements and, when appropriate, combined and grouped them as the basis to begin scenario development. Through these statements, SPC sought policies to guide investment that would influence future growth patterns.

The Next Steps in Scenario Planning

In a 2005 report funded by FHWA and titled Integrating Land Use Issues into Transportation Planning: Scenario Planning, Keith Bartholomew, an assistant professor at the University of Utah, summarized several of the common components and variables included in many exercises in transportation and land use scenario planning. Bartholomew’s research showed that four of the most common components or variables used in scenario planning are the location, density, and mix of development, and the elements of the transportation system.

Through a series of workshops and larger partner meetings, and through facilitated group discussions, SPC was able to establish the participants’ general preferences in terms of common scenario components. Using Bartholomew’s concepts as the basic building blocks, SPC developed six sketch scenarios. Instead of running full-blown scenarios, SPC developed simple variant scenarios without having to do model runs. Sketch scenarios enable the modelers to assess rapidly which ones should be run in more depth.

To assist in this discussion, SPC assigned its draft policies to the six sketch scenarios. The SPC facilitators gave participants an opportunity to review all of the draft policy statements and then rank them in order of importance, developing what is called a value ladder. This value ladder is critical to the process, as it helps participants see which policies have “value” and remain consistent, not only in the sketch scenario process but also in the entire scenario planning process.

The facilitators then helped the participants narrow the six sketch scenarios down to four scenarios, either through combination or elimination. The discussion groups labeled the scenarios the Trend Scenario, Corridor/Cluster Scenario, Compact/Infill/Transit-Oriented Scenario, and Dispersed/Fringe Scenario.

Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green to light green, yellow, orange, and then red. These depict the areas that are more closely aligned to the policy statements and characteristics of a given scenario and therefore more likely to attract development under that scenario. The redder an area, the more likely it will attract development. The red areas here are around current roadways and are dispersed throughout the region with some heavy concentration in the central core, with less dense development represented by the yellow areas along those roadways, representing the Trend Scenario. Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green in areas with little development to light green, yellow, orange, and then red for the most developed areas. In this scenario, the red areas are clustered around roadway corridors and existing communities connected by those corridors.
Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green in areas with little development to light green, yellow, orange, and then red for the most developed areas. In this scenario, development is focused on the central core and areas with good access to transit. Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green in areas with little development to light green, yellow, orange, and then red for the most developed areas. In this scenario, there is little red, with most of the 10 counties being covered in yellow representing a low density of development that is dispersed throughout the region.
Shown here are GIS spatial representations of the Trend Scenario, Corridor/Cluster Scenario, Compact/Infill/Transit-Oriented Scenario, and Dispersed/Fringe Scenario for the SPC region.

The Trend Scenario depicted what the region would look like if existing patterns of investment were to continue.

The Corridor/Cluster Scenario showed what the region would look like if the patterns of investment focused development in and along defined transportation corridors and clustered it around access nodes such as highway interchanges or transit stations.

The Compact/Infill/Transit-Oriented Scenario represented a future where investments would be assigned solely around existing older communities with transit as the primary transportation mode.

The Dispersed/Fringe Scenario adopted investment policies that favored new highway development and investment in infrastructure in low-density areas throughout the region.

Each of the four scenarios maintained a distinct theme such as focusing on corridors, compact development, or dispersed development. The themes are critical in the end because what is being evaluated are the differences between the scenarios.

Each of the four scenarios placed a different emphasis on specific policy statements. For example, if a policy stated that improving transit would be a primary focus of the region, that policy would receive more emphasis in a Compact/Infill/Transit-Oriented Scenario than it would in a Dispersed/Fringe Scenario. The four scenarios depicted not how much the region would grow, but how and where that growth would take place.

A priority outcome of the scenario planning process was to invest in a transit system that will connect people with resources throughout the entire region. This light-rail stop is in Pittsburgh.
A priority outcome of the scenario planning process was to invest in a transit system that will connect people with resources throughout the entire region. This light-rail stop is in Pittsburgh.

At this point scenario planning supplements traditional growth forecasting with important new information. SPC used traditional regional and subregional policy models to develop straight-line population, housing, and employment numbers for each scenario. Then, SPC used an in-house allocation model in combination with the scenario development models to allocate residential and employment growth by traffic analysis zones down to the block level.

 Each projection depended on the block’s attractiveness measures as associated with the policies of a given scenario. For example, a given block might have a transit station yet have poor highway access. In a scenario based on policies that place a greater emphasis on transit, this block will “attract” more residential and employment growth than a scenario with policies that place a greater emphasis on highway access. The key to effective scenario planning is the ability to show those differences in a meaningful way.

By using scenario planning software, SPC presented approximately 40 variables as performance indicators for each of the chosen scenarios and showed how those variables would differ depending on the scenario. Working with all 40 variables could become confusing, so the facilitators again gave the partners in the planning process the opportunity to choose which variables were most important to them. The participants selected the following six variables:

  • Density of development
  • Amount of land developed
  • Households close to highway interchanges
  • Households close to transit stops
  • Regional travel as depicted by regional daily vehicle miles traveled
  • Cost for basic infrastructure

After choosing these variables, the participants reviewed the four scenarios and discussed the pros and cons of each development pattern for their own local community and for the region as a whole.

To afford the public and policymakers a way to assess these differences easily, SPC used GIS technology and scenario planning software to depict visually how the different scenarios and policy emphases would affect the region and show how and where it would grow.

These housing units represent an example of the kind of newer medium-density residential development being built in the suburbs. A desire to increase the density of newer suburban housing was one of the outcomes of the scenario planning process.
These housing units represent an example of the kind of newer medium-density residential development being built in the suburbs. A desire to increase the density of newer suburban housing was one of the outcomes of the scenario planning process.

It is important to emphasize that these scenarios would not predict the specific outcome of a given scenario but would instead highlight the differences resulting from investment policy decisions. The scenario process does not predict the future; rather, it shows the potential differences among alternative futures.

Impacts on Growth Patterns

Each of the scenarios would have different impacts on the region’s growth patterns. For example:

The Dispersed/Fringe Scenario has a lower density development pattern, with development occurring outside the urban cores. The transportation focus is primarily highway-oriented with transit and transit accessibility playing little-to-no role. This scenario would require the expansion of infrastructure, including water and sewer utilities, to previously unserved areas.

The Compact/Infill/Transit-Oriented Scenario has high-density development with a mix of uses and development targeted within or adjacent to core communities. This scenario would take advantage of opportunities for infill development, would reinvest in existing business districts, and would rehabilitate brownfields. In rural areas, preservation of open space would be key. This scenario would be more pedestrian oriented and rely strongly on public transportation. Expansion of existing utilities to accommodate new growth would be minimal.

Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green in areas with little development to light green, yellow, orange, and then red for the most developed areas. The red areas represent roadways and are concentrated in a central core with dispersed concentrations throughout the green area, with yellow areas representing development along those roadways under the final vision scenario. The vision scenario most nearly resembles the Corridor/Cluster Scenario.
This GIS spatial representation of SPC’s vision scenario is the final rendering adopted as part of the region’s 2035 Transportation and Development Plan.

 

Map. Shown is a map of the 10 counties represented by SPC in southwestern Pennsylvania. Colors on the map correspond with levels of development and range from dark green in areas with little development to light green, yellow, orange, and then red for the most developed areas. The red areas represent roadways and are concentrated in a central core with dispersed concentrations throughout the green area, and the yellow areas represent development along those roadways under the final vision scenario. In addition, the map contains purple lines superimposed along some of the red/yellow areas to represent investments in transportation projects included in the plan. The map shows how the planned transportation investments are in accordance with the vision scenario.
Shown here are potential transportation projects overlaid on the vision scenario to evaluate their consistency with the adopted scenario.

The Corridor/Cluster Scenario features medium- to high-density development in centers, clusters, and transportation corridors with a strong multimodal focus, including highways, transit, railways, and waterways. This scenario has excellent access to the urban core with improved transportation operations. Expansion of water and sewer infrastructure would occur along established corridors.

The Trend Scenario is simply the continuation of existing development patterns and policies.

The SPC next developed scorecards to capture the statistical differences between the performance indicators (the six variables listed above) that were considered important through the public process. Participants in the planning process were able to use the statistical and spatial information to help them consider what the region might look like in the future. Using this information, the participants, partners, and regional policymakers were able to select a vision scenario and growth pattern for the region.

How to Use Scenario Planning

Forecasting a region’s growth pattern through scenario planning is just the beginning. As previously mentioned, a scenario is essentially a story about the future that can help people understand the forces of change and the collective choices they have. Once participants and decisionmakers have made the necessary choices, it is important to ensure that future decisions are consistent with that preferred future.

Using the same techniques that were employed in developing the scenario, transportation agencies also can use the scenario planning process to conduct a geospatial and policy analysis for project evaluation and program implementation and development. This helps to ensure that current or future decisions are consistent with the preferred vision for the future. For example, by geographically comparing projects against the vision scenario, transportation planners can evaluate the consistency of a project or series of projects with that vision. Even more important, agencies can develop new programs or initiatives to advance the vision for the region.

For example, SPC’s vision scenario looks to give all areas of the region access to transit. The growth pattern associated with the vision scenario seeks to place more households close to transit in an effort to help achieve that outcome. To promote that scenario, the region needed to look at efforts to advance transit-oriented development.

Through public and private initiatives taking place throughout the region, a number of transit-oriented projects are underway with the support of policymakers and the public. These projects, which seek to place residential and commercial development around transit nodes, are consistent with the policies and intent of the region’s vision scenario and therefore are able to attract the needed funding.

In this era of limited resources, funding, time, and human capital, it is more important than ever that the correct decisions are made when they might impact the long-term future of a region. As the competition for these limited resources increases, a region must use all the tools available to help its policymakers with those difficult decisions. The ability to integrate scenario planning with growth and development forecasting is one of the most valuable tools in providing the needed information to make those decisions.


Lew Villotti is SPC’s planning and development director. Prior to joining SPC, Villotti worked at the Michael Baker Corporation as a project manager. He holds a B.A. in urban affairs and an M.A. in geography and regional planning from California University of Pennsylvania.

W. Kirk Brethauer is SPC’s information systems director in Pittsburgh, PA. Brethauer joined SPC in 1993 and developed its 10-county GIS to support all levels of transportation planning and economic development. Today, he manages SPC’s geospatial analysis, Highway Performance Monitoring System, and information technology. He holds a B.S. in planning and GIS from Pennsylvania State University.

For more information, contact Lew Villotti at 412–391–5590, ext. 302, or lewvillotti@spcregion.org.

ResearchFHWA
FHWA
United States Department of Transportation - Federal Highway Administration