This report showcases approaches to visualization that are used in the Congestion Management Processes (CMP) conducted by metropolitan planning organizations (MPOs). This report has been prepared as one of the inputs to the development of an updated guidebook on the CMP for the Federal Highway Administration (FHWA) and Federal Transit Administration (FTA). It highlights effective visualization practices that are currently in use by MPOs, noting examples of these practices, and the purpose, primary audience, and data and analysis requirements of the visualizations.
The use of visualizations to display information about the congestion of transportation systems is evolving, and may occur both within and outside of the CMP. Applications of the evolving techniques to CMPs can lead to an improved understanding of congestion issues by transportation planning staff preparing the CMP, to more informed decision making by the appointed and elected officials, and finally to the implementation of more effective congestion management solutions.
Clear, concise visuals—such as annotated maps, graphs, photos, illustrations, and videos—can allow the audience to quickly understand an important topic more effectively than through statistics and numerical tables. Consequently, visualization can be a very effective tool for presenting transportation performance data and information in ways that can be understood and absorbed by various audiences, including technical staff, transportation decision-makers, and the general public.
Visualization serves three essential functions within an MPO’s CMP, from the information gathering that occurs at the beginning of the process to the dissemination of information at the end. Visualization:
These three functions are related, but differentiated primarily by the intended use (helping with the detailed technical analysis, developing a staff consensus, or decision-support and public education). Many CMPs have visualizations with components of each of these broad purposes. Typically information needs drive analysis and data-and in the reverse, the availability of data, analysis methods, and display techniques impact the information available for decision making.
Several MPOs develop materials that are intended to present the information collected and analyzed through the CMP to the public, and disseminate these either through reports or websites. While these materials are generally broad in scope, they often include visuals such as maps of congested locations or bar graphs of changes in transportation system use over time, which are intended to convey a simple message about congestion in the area, and how it relates to other parts of the planning process. For example, if a major project was recently implemented in an effort to mitigate congestion in an area, a before-and-after visualization (such as a color-coded map of level of service, a graph of vehicle delay, or a series of photographs of actual conditions) could be used to convey the impact the project had. Similarly, if one location within an MPO stood out as a result of the CMP analysis as an area most in need of congestion mitigation, a visual could be used to express that to the public. The primary concern in developing visualizations for the public is to ensure that they are easy to understand and that the intended message is clear.
Visualizations, especially map-based, can also serve as a valuable tool in organizing data and making it easier to analyze on a technical level. Some visualizations are more schematic in their representations of data patterns, or blend schematic with map-based formats. The fact that much of the data collected for the CMP is geographically-based (tied either to an area, a corridor or a spot location) makes mapping especially important for practitioners, both within an MPO and at partner agencies outside the MPO. Mapping can be done on paper, through a GIS program, or through an online mapping service, depending on the data and the MPO’s capabilities. Graphs and photographs can also be effective tools in helping practitioners analyze and apply the large volumes of data that are often collected or gathered as part of a CMP effort. If kept relatively simple and easy to read, these display maps of technical data with concise annotations can also be an effective tool for reaching the general public.
MPOs create visualizations geared specifically toward different audiences. These visualizations are accessible to everyone, but may be most useful for specific sectors of the population. Some visualizations are more technical and are most practical for internal use as opposed to public consumption. For instance, visualizations depicting detailed level-of-service likely are most valuable for decision-makers and planners in determining where to focus congestion management efforts. For example, Puget Sound Regional Council uses a geodatabase with shapefiles showing land use attributes, congestion and level-of-service at points in the region in order to help planners better identify regional needs based on multiple factors.
Conversely, visualizations that show "before and after" alternatives are constructive for the public and stakeholders without expertise in transportation planning or analysis, since these visualizations clearly and visually lay out the results of different congestion management options. Scenario development can also be used to educate the public on the impacts of different land use decisions on transportation needs in a region. MPOs such as the Wilmington Area Planning Council house interactive maps developed using Google Maps, which allow viewers to pan and zoom so they can see the data on either a regional or a detailed scale. For example, people can zoom to the street level within their community or neighborhood to find the specific data for that area. The Atlanta Regional Council uses "travel time shed" diagrams to show policymakers how long it takes to travel from the downtown area outward.
There are no cut-and-dried rules for determining which visualization types are most useful for specific audience types. However, it is clearly necessary to consider the intended audience and use in determining the best visualization approach to use.