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Congestion Management Process Guidebook

Chapter 4 - Using Visualization as a Communication and Analysis Tool

The use of visualizations to display information about congestion of transportation systems is evolving, and may occur both within and outside of the CMP. Applications of the visualization techniques to CMPs can lead to: (a) an improved understanding by transportation planning staffs preparing the CMPs, (b) more informed decision making by appointed and elected officials, (c) the implementation of more effective congestion management solutions, and (d) greater acceptance and appreciation by the general public and interested stakeholders.

4.1 - The Role of Visualizations in the CMP

Clear, concise visuals—such as annotated maps, graphs, photographs, illustrations, and videos—can often communicate important information 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:

Visualizations, especially maps, can also serve as valuable tools in organizing data and making it easier to analyze on a technical level. Since much of the data collected for the CMP is geographically-based (tied either to an area, corridor, or spot location), mapping—whether on paper, through a GIS program, or through an online mapping service—is especially important for practitioners, both within an MPO and at partner agencies outside the MPO, to better understand the geographic patterns in the data. 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.

These display maps of technical data can also be an effective tool for reaching the general public, if they are kept relatively simple and easy to read. 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 that are intended to convey a simple message about congestion in the area, which can then help people understand the issue as it relates to other parts of the planning process. For example, an MPO may use a visualization developed as part of its CMP to illustrate a point in its MTP.

4.2 - Data Used in Visualizations

Visualizations are tools that summarize an extensive amount of data into a more easily-comprehensible set of information displays that allow viewers to quickly assess and interpret the information. This data can come from multiple sources and may be tied to the performance measures developed in Action 3. Data may be directly collected by the MPO utilizing in-house staff and resources or temporary personnel, or through consultants. Data may also be gathered by the MPO from external sources that collect data for a different main purpose, such as archived ITS data from traffic flow detectors used by transportation operations organizations. In creating visualizations, there is a distinction between the observed data that some MPOs use and simulated or forecasted information. When the CMP is dealing with future scenarios, modeling of information is necessary. When dealing with existing or past conditions, the observed data is often more accepted by decision-makers.

Visualization can be an effective tool for organizing, interpreting, and using large volumes of data and information, and for presenting the most pertinent information to the public. Data activities take many forms, ranging from the manual collection of speed data through travel-time runs to the gathering of vast data repositories available through Intelligent Transportation System (ITS) and Advanced Transportation Management System (ATMS) activities. In many cases, data is gathered from existing data sources at partner agencies, such as crash databases from the state police or state DOT. Ultimately, visualizations are an illustration of data collected and presented in a format that allows the observer to more rapidly respond to an image than would be possible when simply looking at raw data.

4.3 - Visualization Methods Used in CMP Activities

A wide range of different types of visuals can be used as part of the CMP. Several examples are noted in this section.

Displays of Measured Congestion based on Observed Data

These are maps of current data collected in the CMP monitoring process. Examples include:

The example in Figure 5, from the Capitol Region Council of Governments in Hartford, uses a color-coded schematic map to display data collected for the regional freeway ITS system. Color-coded maps are a simple, easily-comprehended method of visualizing this information, which in this example is the average speed in the peak direction in the 7:00 to 8:00 AM time period on the regional freeways.

Figure 5. Freeway System Display of Speeds or Congestion Using Color Coded Lines, Hartford, CT

Average Weekday 7:00 – 8:00 A.M. Inbound. Average speed on area freeways, inbound direction for the average weekday, 7:00 to 8:00 A.M. This map has five freeways radiating out from the center of the region. Different colors show the average speed of segments.

Source: "Transportation Monitoring and Management Report: Metropolitan Hartford Area, 2005", Capitol Region Council of Governments, 2007, www.crcog.org.

More complex maps, such as speed-time-location visuals, are more effective at showing detailed information available from ITS, such as the locations of bottlenecks, the extent of backups, and the duration of congestion. Figure 6, from the Chicago Metropolitan Agency for Planning, is a detailed speed-time-location display based on archived ITS detector data from a private sector data provider. As noted with the display, the graph shows average directional speed by location along the expressway corridor as well as by time-of-day throughout a selected sample day. This display shows for example that the westbound PM congestion conditions occurred over a two-hour period between 4:00 and 6:00 PM, and were concentrated between about milepost 4.0 and milepost 5.5, with the most concentrated congestion being between mileposts 4.5 and 5.0. The display shows eastbound congested conditions as well. It enables planners to focus in on the most densely congested areas and view the extent of congestion around each area so that the seriousness of the congestion in terms of delay can be assessed, and to communicate this complex information to the public in an understandable way.

Figure 6. Congestion Display Showing Speeds by Location and Time of Day for a Roadway, Chicago

Congestion Display Showing Speeds by Location and Time of Day for a Roadway, Chicago. Click for more information.

Source: Chicago Metropolitan Agency for Planning CMP Performance Measurement Website (2009 data), http://www.cmap.illinois.gov/mobility/roads/cmp/performance-measurement

Displays of Forecasted or Modeled Conditions

One common analysis approach in many CMPs is to use model results (whether current or forecasted) as a primary information source. Since models themselves are built using geographic data, this information can be easily displayed graphically in the form of maps. Displays include:

Travel time contour maps can be made using any type of speed/travel time data, but are typically made using modeled results rather than observed data (or sometimes with a combination of the two), to ensure full coverage of the region. Figure 7 provides an example of travel time contour maps. The Atlanta Regional Commission shows the travel time during the peak period between downtown Atlanta and all points within the MPO area, as well as the non-congested free-flow condition, using 15-minute color-coded bands. This provides a quick snapshot of the effects regional congestion have on regional travel times.

Figure 7. Travel Time Contour Map, Atlanta

Travel Time Contour Map, Atlanta. Click for more information.

Source: "Congestion Management Process Update 2005: Technical Memorandum 5", Atlanta Regional Commission, 2005, www.atlantaregional.com.

Displays of Congestion Trends Observed over Time

The ongoing data collection that occurs as a result of the CMP can also be a source of information on congestion trends over time. Several MPOs have developed methods of displaying this trend data on maps, which can be useful tools in determining whether implemented CMP strategies are effective at addressing congestion concerns in certain corridors. Common approaches include:

The North Central Texas Council of Governments (NCTCOG) displays results of traffic condition trends over several years side-by-side. It shows the average temporal variability within each year, the spatial variability along the roadway corridor, as well as the year-to-year trends of both. In addition to the year-to-year temporal variability, this type of visual can be used to show the temporal variability within the hours of a typical weekday, by day of the week, month of the year, or by season. Each of these may be of different interest to the general public, planning staff, and decision-makers. This provides detailed information useful for tracking change over time, and can be a helpful tool in determining whether implemented CMP strategies are effective at addressing congestion concerns in certain corridors.

Figure 8. Display of Measured Congestion Levels over Time, Dallas

Display of Measured Congestion Levels over Time, Dallas. Click for more information.

Source: "2007 Traffic Conditions in the Dallas-Fort Worth Metropolitan Area", North Central Texas Council of Governments, 2007, www.nctcog.org.

Displays of Reliability Data

These types of displays utilize information collected on the reliability of transportation systems. Examples of these types of graphics include:

The Capital District Transportation Committee (CDTC) in Albany uses derived metrics such as the planning time index - the CDTC maps use line widths to display base travel time and the additional travel time built into travel time planning to account for non-recurring congestion and delay. Figure 9 shows examples of the reliability visuals developed by CDTC.

Figure 9. Display Showing Recurring and Non-recurring Congestion, Albany

Display Showing Recurring and Non-recurring Congestion, Albany. Click for more information.

Source: "The Metropolitan Congestion Management Process", Capital District Transportation Committee, 2007, www.cdtcmpo.org.

Displays of Multimodal and Transit Data

Many MPOs include transit service and bicycle/pedestrian facilities in their analysis of congestion, both in terms of system performance and as a potential congestion management strategy. Several approaches can be used to display this information, both from the perspective of the availability of options/system performance and potential as a congestion management strategy:

The Hillsborough County MPO in Tampa has an effective way of displaying information on the availability of multimodal facilities and services, in comparison with areas of highway congestion, through a series of strip maps shown side by side, as in Figure 10. These maps are well-suited for analysis of whether the multimodal system is aligned with the congestion-mitigation needs of the highway system. Therefore, these maps can be utilized to identify those areas where needs are not met, and plan for future construction of bus routes or increased bicycle/pedestrian facilities necessary for congestion mitigation.

Figure 10. Display Showing Transit, Road, Bicycle, and Pedestrian Measures, Tampa, FL

There are three schematic maps in this figure, showing different modes serving a particular corridor. All three maps use the same base map that shows local roads. The first map shows bus routes serving the corridor, the second map shows the volume to maximum service volume ratio for road segments, and the third map shows bicycle and pedestrian facilities. Pedestrian facilities are shown as the percent of the road segment with sidewalks.

Source: "Congestion Management System Performance Report", Hillsborough County MPO, 2005, www.hillsboroughmpo.org.

Displays of Recommended Strategies for Implementation

Many MPOs develop graphics to show the strategies that are recommended in the CMP. This provides an easy-to-read and understand one-stop source for location-based information on the strategies in the CMP. Maps can be developed to cover specific spot locations, corridors, or entire regions. The example in Figure 11, from the Miami-Dade MPO, shows the strategies recommended as the result of a corridor analysis in their CMP.

Figure 11: Display of Recommended CMP Strategies, Miami-Dade, FL

Display of Recommended CMP Strategies, Miami-Dade, FL. Click for more information.

Source: Miami-Dade MPO LRTP Interactive Project Tool: www.miamidade2035transportationplan.com/ProjectGuide/

Charts, Graphs, and Tables

Charts, graphs, and tables are a clear, easy to understand way of visualizing data and analysis results. Examples include:

Figure 12, from the Washington Metropolitan Area Transit Authority, used in the National Capital Region Transportation Planning Board’s CMP, clearly shows the relative levels of congestion on several transit lines in an easy-to-understand manner. It alerts the public to future capacity problems along certain lines, and can be used to help show policy makers the need for more funding or management and operations strategies for the Metrorail system to meet the needs of its ridership growth.

Figure 12. Display of Transit Congestion Using Simple Color Coding, Washington, DC

Display of Transit Congestion Using Simple Color Coding, Washington, DC. Click for more information.

Source: MWCOG CLRP Website, http://www.mwcog.org/clrp/performance/congestion.asp.

Use of Visuals to Differentiate among CMP Strategy Options

Beyond using visualizations to convey data, several MPOs use photo-simulation and other visual tools to conceptually convey the ideas presented as potential CMP strategies. The Capital District Transportation Committee (CDTC), the MPO for the Albany area, uses photographs and photo-simulations to show the public what different CMP strategies would look like on the ground, as shown in Figure 13. The visuals below show an existing corridor in the Albany area (top) and an example of what this corridor could look like with improvements to the bicycle and pedestrian infrastructure (bottom). The MPO uses these visuals to help the public understand differences between strategies outlined in the CMP.

Figure 13. Photo Simulation of Potential Strategy Implementation, Albany, NY

This graphic shows two photographic images. The first is of the existing conditions along a wide corridor with a wide travel lane in each direction and a striped median. The second image is a photographic simulation of the concept for the corridor. There is now a large, landscaped median in the center of the road with grass and a tree, much narrower travel lanes, a bicycle lane, and on-street parking on one side of the street.

Source: Capital District Transportation Committee, www.cdtcmpo.org

Use of Video or Animation

Multimedia displays can appeal to audiences by providing dynamic information. Examples include:

The video in Figure 14, from Evans City in the Southwestern Pennsylvania Commission (SPC), demonstrates the result of SPC’s regional traffic signal program, which is an outgrowth of its CMP. It utilizes an appealing visualization to make the results of the program more tangible and real, allowing drivers to see exactly how change will affect them. The display shows traffic conditions before and after the implementation of several CMP strategies at this location, and highlights the vast improvement in travel time through the corridor (as both videos are played simultaneously). On one side of the screen, the viewer can see that after signal re-timing, the driver is able to travel the roadway in 3 minutes and 1 second, while before signal re-timing it took 6 minutes, 10 seconds.

Figure 14. Video Demonstrating Result of Strategy Implementation, Pittsburgh, PA

Video stills Demonstrating Result of Strategy Implementation, Pittsburgh, PA. Click for more information

Source: SPC Transportation website:http://www.spcregion.org/trans_ops_traff.shtml

4.4 - Lessons Learned on Effective Visualization

The primary lesson learned with regard to visualization of the CMP is that visualizations intended for public consumption must be easy to understand, and must clearly convey their intended message. While graphics should not be littered with superfluous information, and should not attempt to show too much information all at once, too simplistic representations of the data may skip over or trivialize important interrelationships that need to be better understood to effectively select and gain support for implementing a particular congestion management strategy.

Some visualization methods can be costly to perform due to intensive labor needs, specialized skills or training, expensive technology, or the amount/type of data required. However, visualizations do not need to be expensive to be effective - many of the methods above could be developed relatively simply, using either in-house staff or hired consultants. The type(s) of visualization used in the CMP will vary based on the type of information being displayed, the intended audience, and the resources available.

It is sometimes difficult to overcome the perception of visualization as a frill that is not a necessary part of the CMP process. However, visualization plays a major role in organizing the spatial and temporal data collected as part of the CMP and in communicating the results of the CMP analysis to the public and elected officials. The primary goal of the CMP is for the congestion analysis to be a major factor in the development of long-range plans and short-range funding plans developed by MPOs, and to influence the selection of projects that are included in these plans. For this to happen, it is vital for the congestion data collected and analyzed through the CMP to be distributed in a format that can exert that influence on the rest of the MPO planning process. Visualization is a very effective way of doing this.

Updated: 01/08/2014
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