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FHWA Scenario Planning Guidebook

Phase 5. What Impacts Will Scenarios Have?

Assess scenario impacts, influences, and effects.

Phase 5 focuses on analyzing scenarios. Scenario analysis typically involves assessing the impacts, influences, and effects that various scenarios exert on selected indicators. As described in Phase 3, indicators are statistical values (e.g., level of employment) or groups of values that are used to compare two or more scenarios. While Phase 5 focuses on scenario analysis through use of indicators, these indicators might have already been developed or considered in earlier phases, particularly Phase 4.

When analyzing scenarios, agencies can consider either a qualitative or a quantitative approach. Using a qualitative approach, agencies could utilize working groups or roundtables to facilitate discussion and brainstorming about scenario impacts. Agencies considering a quantitative approach could use the travel demand model or a GIS-based scenario analysis tool.

There are several steps to Phase 5. Agencies can:

Each step is listed below, along with associated key questions that agencies can consider. Some steps provide examples of additional issues or questions for further consideration.

Step 5.1: Develop or identify indicators to compare scenarios.

Developing Scenario Indicators

A variety of applications and models can be used to help identify and develop indicators:

  • The travel demand model can be used to gauge transportation accessibility.
  • GIS-based applications can be used to assess sidewalk availability, buffer areas for transit ridership, or other impacts.
  • The Environmental Protection Agency's Motor Vehicle Emissions Simulator (MOVES) model can be used to assess air quality or greenhouse gas emissions.

Examples of indicators used in previous scenario planning efforts are listed below.

Environmental/land-use indicators

  • Acres of non-urbanized land
  • Percentage of farms and forests

Community livability indicators

  • Percentage of population living in clustered communities
  • Percentage of population with access to transit
  • Annual gallons of gas consumed

Jobs/housing indicators

  • Number and/or percentage of jobs located near affordable housing
  • Change in average commuting times

Transportation system indicators

  • Number of highway congested hours
  • Vehicle miles traveled by mode
  • Percentage of work or all trips by mode

Climate change indicators

  • Greenhouse gas emissions by sector and county
  • Greenhouse gas emissions due to vehicle miles traveled
  • Acres of land deforested for development

Step 5.2: Use indicators to identify scenario impacts.

Step 5.3: Obtain feedback on analysis, and refine scenarios as needed.

Developing a Matrix for Scenario Analysis

TJPDC used a matrix to illustrate scenario performance.* The matrix compared scenario outputs with general as well as specific indicators developed from the Sustainability Accords principles.

The matrix, shown below, includes analysis of each of the four scenarios (dispersed, town centers, CoreL, and CoreM) developed by TJPDC. The italicized figures under the dispersed scenario column indicate that this scenario scored lowest on every measure compared with other scenarios. The low scores indicate the public's growth preferences in rejecting a dispersed, low-density pattern in favor of clustered, enhanced communities along major corridors and key crossroads.

The numbers under the scenario columns show the comparison of each scenario's land-use and transportation networks with the measures in the left-hand column. For example, only 55 percent of land cover in the dispersed scenario was composed of farms and forests.

Measure / Sustainability Accord Dispersed Town Ctr CoreL CoreM
Bold-faced measures correspond to the Sustainability Accord measures
Red/Italics — Comparatively lowest
Pct. Farms and Forests
Retain peer_exchange/habitat/farms/forests
55 64 65 65
Pct. Developed
Retain peer_exchange/habitat/farms/forests
45 36 35 35
Pct. Living in Clustered Communities
Optimize use/cluster/human scale
13 61 68 68
Pct. Non-auto Trips
Transportation Alternatives
4 15 18 18
Annual Gallons Gas Consumed (billions)
Conserve Energy
155 121 110 114
Pct. Travel Congested
Employment/Education Access
44 27 20 21
Water Quality and Quantity
Water Quality and Quantity
Poor Good Good Good

* For more information about TJPDC's scenario planning effort and the analysis matrix, see www.tjpdc.org/community/epi.asp.

Phase 5 Outputs

Phase 5 has several possible outputs, including a list of indicators to compare scenario outcomes and a qualitative or quantitative assessment of scenario impacts. Some agencies have used tables or matrices to outline how scenarios perform against the chosen indicators. Other agencies utilizing a qualitative scenario assessment approach have summarized scenario performance in white papers or other documents, or through discussion in focus groups, roundtables, or expert panels.

Updated: 05/14/2014
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