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|Federal Highway Administration > Publications > Public Roads > Vol. 77 · No. 2 > Predicting the Future?|
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.
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.
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.
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.
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.
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.
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.
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:
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.
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.
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 firstname.lastname@example.org.
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