National Academies Press: OpenBook

Visualization of Highway Performance Measures (2022)

Chapter: Chapter 2 - Literature Review

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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2022. Visualization of Highway Performance Measures. Washington, DC: The National Academies Press. doi: 10.17226/26651.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

8 Summary of Published Works to Date This chapter summarizes a review of the existing literature and guidance currently avail- able about visualizing performance measures and the relevance of that material to the overall synthesis. Due to the current evolutionary nature of the topic, much of the most recent information is addressed in the literature primarily through websites, conference presentations, or other forms of presentations that address more retrospectively what is already being put into practice. While there is ample literature available on visualization in general and on the visualization of data in other fields, particularly in the realm of science education, there is a relatively limited body of technical methodological research, academic publications, and reports in technical journals specifically addressing the topic of visualizing transportation data. Most of the aca- demic work regarding the visualization of transportation data has been on a micro level, in terms of seeking to apply visualization of data to location- or scenario-specific challenges, as opposed to how one might best apply the practice to a DOT system as a whole. As subsequent chapters will illustrate, much of what has been found in the current state of the practice has been derived from in-the-field innovation by individuals in DOTs throughout the nation. Therefore, although academic research is included in this review, it largely focuses on guidance that has been previ- ously published by national transportation organizations and the publications by researchers outside of the field of transportation. To explore complex visualizations not addressed in this synthesis, there are over one hundred video presentations from TRB Visualization in Transportation Symposia available on the TRBVIZ website about a wide variety of specialized topics surrounding data visualization (National Transportation Research Board Committee on Visualization in Transportation 2020). For example, the website includes “MAP-21 PM3 Deep-Dive Visual Analytics,” “Color Fundamentals for Visualization, Creation, and Exploration,” and “Visualizing Urban Freight Movement by Leveraging Mobility Data Portals” (Ayers 2019, Rhyne 2019, Yuksel 2019). The publications can be divided into two main groups: generalized guidebooks produced by visualization experts and enthusiasts and industry-specific publications. Both of these groups have impacted and been impacted by the state of the practice over the last 20 years. This review will first address generalized publications and then move on to a more in-depth discussion of the industry-specific literature currently available. Generalized Publications There are a number of published books and blogs on visualizing data that have been written by private subject-matter experts and enthusiasts that speak to common issues of theory and prac- tice in the visualization of data in general. The following review is not exhaustive but intended C H A P T E R   2 Literature Review

Literature Review 9   to provide an overview of some recent publications. The review also elucidates the literary and theoretical context within which DOT practitioners and innovators have been working, pre- sented in detail in the case examples in Chapter 4. The referenced publications on the visualization of data go back to the 1983 publication by Yale professor Edward R. Tufte, The Visual Display of Quantitative Information, initially believed to be relevant only to those interested in the then-dawning field of computer graphics. In the publication, Tufte lays out the foundations of theory and practice for the design and display of data graphics, including charts, graphs, and tables, and how to use them most efficiently for quick data analysis. Tufte went on to expand this foundation into a set of more widely appli- cable principles incorporating clarity of design in his next book, Envisioning Information (1990). He capped off his trilogy of contributions to the nascent field of data visualization with the 1997 publication of Visual Explanations: Images and Quantities, Evidence and Narrative. In this final volume he presented a vast array of real-life examples of how the efficient visualization of statistical data significantly contributed to decision-making processes. It is in this volume that he introduced the concept of narrative, or what is called storytelling by later authors, and the significance of resonating with an intended audience, ideas that can be widely found in the state of the practice today. There is significant literature in the general area of data visualization, and what follows is a summary of selected literature. Originally published in 2007, Garr Reynold’s book Presentation Zen: Simple Ideas on Pre- sentation Design and Delivery just went into its third edition (2019). In this book, Reynolds emphasizes the themes of connecting with an audience and what he argues is the necessity of simplicity and clarity in doing so effectively. He discusses the framework of storytelling and narrative in making his recommendations for how to best accomplish these goals. There is a companion blog available online, also titled Presentation Zen, that carries on these discussions in terms of real-life examples. One of Reynold’s most emphasized points is that design matters. He posits that visualiza- tion of data is about making communication as easy and clear for the audience as possible. For example, he argues that empty space is not nothing. It is a powerful something. It is the area that helps guide the eye to the most important information. He also discusses the importance of the principle of flow in a design and how it helps guide the audience the from beginning to the “ah ha” moment. Reynolds goes on to name four principles as important guides in the design of effective visualizations: contrast, repetition, alignment, and proximity. He explains that sophisticated design may begin with a concept that is memorable “at-a-glance,” but to execute the design typically requires addressing many small adjustments that result in a good informa- tion graphic. For example, Reynolds emphasizes simplicity in terms of how the visual will look, asking questions like: “What elements (text, chart, map, icon, table, photo) are included?,” “How large is each element?,” and “What is the first thing the audience should see?” He also addressed the issue of audience expectations when it comes to simplicity, such as placing a title in the upper left-hand corner because it is the place audiences expect to see a title. Reynolds suggests that it is most effective to work with such audience expectations rather than against them, as this increases clarity and simplicity. In his book The Back of the Napkin: Solving Problems and Selling Ideas with Pictures, pub- lished in 2013, author Dan Roam argues that everyone is born with a talent for visual thinking, which makes communicating ideas visually a relatively intuitive process. More importantly, he puts forward his ideas about the power that even simple drawings (such as on the back of a napkin) can have in the ability to organize and analyze information, streamlining the problem- solving process.

10 Visualization of Highway Performance Measures In this book, Roam asserts that data visualization assists with problem solving and suggests that “the heart of business is the art of problem solving.” He goes on to ask, “What if there was a way to more quickly look at problems, more intuitively understand them, and more rapidly convey to others what we’ve discovered?” Roam then lays a foundation for making strategic choices in creating data visualizations by explaining that there are six ways we see, which relate to six ways we can then show what we see. Figure 2 is an example from a chart that Roam uses to simplify his theories on the relation between thinking about questions of who/what, how much, where, when, how, and why, and the different ways that information can be shown. For example, if we are seeing a who or a what, one of the simplest ways Roam says to visually represent that information is with a portrait of a person or photograph of an object or place. However, if we are seeing how much of various categories there are and how they relate to one another, Roam says one of the simplest ways to visually represent that is with a chart or graph. Figure 3 shows another way Roam suggests further refining the best type of visual to use, for a particular type of data and for a specific level of an intended audience. The intention of the chart is to help the practitioner select first, on the left, which type of data they want to represent. For example, if the practitioner wanted to represent information about the question of who Roam’s previous chart identifies, the simplest way to represent that could be a portrait. This more complex chart then asks the practitioner to select the importance or necessity of certain visual qualities, based on the desired complexity of the data and/or visualization decided to be most appropriate for the intended audience. Roam labels the visualization/choice categories with the acronym “SQVID.” The filter is based on the following questions regarding the informa- tion that the practitioner should ask to evaluate their data and desired visual: • (S) Does the visual need to be simple or elaborate? • (Q) Does the visual need to convey quality of design or quantity? • (V) Does the visual represent vision or execution? • (I) Does the visual communicate an individual element or a comparison of many items? • (D) Does the visual communicate change or an as-is condition? Figure 3. Roam’s SQVID filter (Source: Roam 2013). Figure 2. An example referencing Roam’s six ways we can show what we see (Source: Roam 2013).

Literature Review 11   Storytelling with Data: A Data Visualization Guide for Business Professionals by Cole Nussbaumer Knaflic, published in 2015, speaks to the increasing trend toward visualization that is occurring in the marketplace at-large and toward the demand that exists for increasingly more informed guidance on the subject. This book is organized around the theories of audience, clarity of design, and visual storytelling, all essential principles initially introduced by Edward Tufte’s seminal works. In 2019, Knaflic also published a companion volume more focused on practical application, titled Storytelling with Data: Let’s Practice! Dona Wong was chosen as a keynote speaker for the 8th International Visualization in Trans- portation Symposium held in Washington, DC in 2017. Her presentation “Telling Compelling Stories with Data” featured her book, The Wall Street Journal Guide to Information Graphics: The Dos and Don’ts of Presenting Data, Facts, and Figures (2013), distributed to all attendees. She presented on common pitfalls and how to avoid them. Her very practical guidance points out her suggestions for best practices and common pitfalls of the most-used visualizations, including tables and bar, line, and pie charts. Guide to Information Graphics provides many clear examples for designers to consider. Figure 4, concerning high impact visualizations, is just one example from the book that illustrates the significance Wong places on working with what an audience expects, similar to the point that Garr Reynolds makes in Presentation Zen. Dr. Stephanie Evergreen has built her career on the critique and improvement of how pro- fessionals communicate data. Her website, Evergreen Data, hosts a blog discussing her theories and their practical application. Her book, Effective Data Visualization (2019) includes a chapter on recommendations for dashboard design and construction, reflecting the rapid expansion of the use of online dashboards to communicate data in a wide variety of fields and industries. Both the book and the website provide detailed theory and practical real-world examples of Evergreen’s methods to create effective data visualizations based on her research. Nancy Duarte’s book, DataStory: Explain Data and Inspire Action Through Story (2019), focuses on the singular concept of storytelling as an effective framework for the communication of data. She centers her guidance and employment of other principles, such as audience and clarity, around how to design and create visualizations that tell stories in a way that emotionally impact their audience and hence inspire and motivate direct action. She characterizes her approach as taking a “data point of view.” This accentuates that without data, there is no story to tell; it is through analyzing data that one determines if there is a story to be told, what that story is, and what, if any, recommendations for action should be made based on that story. According to her perspective, it is the answers to these questions that pro- vide the overall point of view and ultimately set the course for designing the most appropriate visual representation of that story in a manner that will resonate with the intended audience to inspire action. Duarte’s previous book, Resonate: Present Visual Stories that Transform Audiences, asserts that facts alone fall short. She explains that there can be piles of facts and the story may still fail to make any impact on its intended audience, so it is not the information that is important, but more so the emotional impact of that information that creates an effect. In this book, Duarte identifies that reporting performance measures may include “just the facts,” but converting the facts into useful information, and information into sustained impact, is the crux of the challenge. Therefore, it is crucial, in her estimation, that one determine the most effective way to trans- form the facts into a visual narrative that resonates with the intended audience (Duarte 2010). There are a number of general publications dealing with specific design aspects of visual- ization, such as the use of color. A representative example of this type of work can be found in Theresa-Marie Rhyne’s book Applying Color Theory to Digital Media and Visualization. In this book, Rhyne posits that color can be effectively used as the most impactful element to focus the

Figure 4. An example from Wong’s The Wall Street Journal Guide to Information Graphics: The Dos and Don’ts of Presenting Data, Facts and Figures (Source: Wong 2013).

Literature Review 13   attention of the audience on the area that tells the story. Using color well reinforces the message. Using color in visualizing a performance story is a marriage between art and science. One sees the entire picture, and all the colors at once. e elements of color, shown in Figure 5, are used together to help tell the story (Rhyne 2017). Rhyne elaborates on how eective design can be shown in black and white and still commu- nicate the story. For example, if the primary distribution is expected to be a personal printer, black and white may be the best design choice. However, she points out that color has the benet of adding another dimension to focus attention on important information. Rhyne, similar to many general knowledge sources on color theory, illustrates that there are multiple possible considerations when selecting colors in a data visualization. Some of these considerations can include, but are not limited to, the following: • Psychological relationships to colors; for example, what does a reader think of when seeing red or orange? Not everyone will have the same reaction, but there are some common expectations. • Contrast will have a profound eect on the legibility of a visual. Dark red text on black is dif- cult to read. Some audience members are color blind, and require strong contrasting values to distinguish between color pairs. • Balance, or the relationship of major and minor elements, impacts where the eye is focused. • Color theory studies the relationships between colors. Analogous colors that are close to each other can be both visually attractive and communicate eectively. Contrasting colors on oppo- site sides of the color wheel will intensify the color of both. Adding white, black and/or gray can add sophistication and nuance to the overall impact (Adobe 2021). ere are a number of scientic studies into questions of how eective data visualization is for the communication and recall of information and why. An example of these studies and how they contribute to a deepening understanding of the practice is the 2015 Harvard study on visualization and memory, “Beyond Memorability: Visualization Recognition and Recall.” In this study, the authors argue that the most memorable visualizations are those that are memo- rable “at-a-glance.” ey explain the science behind this is that visualizations are memorable if they require less eye movement to recognize the visualization, hence they can be more quickly retrieved from memory. More signicantly, “when these visualizations are retrieved from memory, many details of the visualization are retrieved as well” (Borkin et al. 2015). Theory Relationship between colorsTheory Relationship between colors Psychological Relationship of color to our feelings Psychological Relationship of color to our feelings Contrast Relationship of light to dark Contrast Relationship of light to dark Balance Relationship of Major and Minor areas Balance Relationship of Major and Minor areas Figure 5. Key concepts from Rhyne’s Applying Color Theory to Digital Media and Visualization (Source: Broen).

14 Visualization of Highway Performance Measures The Harvard study also speaks to possibilities of why many of the initial principles identified by Tufte have endured in both theory and practice over the last several decades. These prin- ciples again include simplicity, clarity, working with expectations of an intended audience, and use of narrative strategy. The study speaks quite specifically to a particular strategy of “perfor- mance journalism,” developed by Washington State DOT (WSDOT). This strategy uses care- fully crafted textual headlines in conjunction with data visualizations (addressed in detail in the WSDOT case example in Chapter 4 of this document). The authors of the study explain the effectiveness of such strategies in the following way: Titles and text attract people’s attention, are dwelled upon during encoding, and correspondingly contribute to recognition and recall. People spend the most amount of time looking at the text in a visualization, and more specifically, the title. If a title is not present, or is in an unexpected location (i.e., not at the top of the visualization), other textual elements receive attention. As exhibited by these results, the content of a title has a significant impact on what a person will take away from, and later recall, about a visualization . . . Note that prior psychology studies have demonstrated that concrete, imageable words (those that can be easily imagined or visualized) are easier to remember than abstract ones. (Borkin et al. 2015) Industry-Specific Literature The article “Bridging the Gap between Agencies and Citizens: Performance Journalism as a Practical Solution to Communicate Performance Measures and Results,” published in a 2008 issue of TRB’s journal, Transportation Research Record: Journal of the Transportation Research Board, explores WSDOT’s approach of what it calls “performance journalism” for communicating performance measure data to a broadly defined audience, including the public, the media, and policymakers. The author explains the concept in the following way: “Effective communication of performance information is more than just publishing data and text. It requires an agency to tell its story and apply analytical and journalistic methods” (Bremmer and Bryan 2008). This concept is covered more thoroughly in Chapter 4, which provides an in-depth case example of WSDOT’s methods and practices. However, their conception of “performance jour- nalism” is one example of a strategy that employs a variety of the theories that are found in both popular and industry-specific literature. It may be of particular educational merit to examine WSDOT’s practice of performance journalism in conjunction with Duarte’s theories regard- ing the use of storytelling from a data point of view. Performance journalism is applying the journalistic principles of ethical responsibility for factual reporting and communicating infor- mation in a manner that is clear, concise, and at a level suitable to the understanding of the gen- eral public. This method combines the use of brief but informative headlines with visualizations that are strategically designed to achieve the maximum level of both simplicity and effectiveness. In “Bridging the Gap between Agencies and Citizens: Performance Journalism as a Practical Solution to Communicate Performance Measures and Results,” Bremmer and Bryan make the following recommendations based on their examination of WSDOT’s practices: Can the graph or table be clipped and pasted into another document, and would the information still be clear and transparent? Can the graph stand alone? Treat headings as headings describing text would be treated. Be succinct, yet clear. If the topic is complex, use multiple lines and subheadings to convey the information. Within seconds of viewing the page, the reader should understand the graph’s content and purpose. Use footnotes liberally to explain data sources and anything else the reader needs to know to draw the right conclusions and understand the analysis and data limitations. (Bremmer and Bryan 2008) Figure 6 provides an example used by Bremmer and Bryan in their article to illustrate their argument regarding the impact that even the smallest decisions, such as labeling or choos- ing whether or not to use a graphic effect, can have on simplicity and relative effectiveness. In the figure, the top chart is presented with a number of graphic embellishments and without

Figure 6. A comparative example (Source: Bremmer and Bryan 2008).

16 Visualization of Highway Performance Measures a “headline” that communicates the most salient point represented in the visualization. The bottom chart is presented without the graphic embellishments and with a relevant headline. The authors assert that the bottom chart, created using the general practices employed by WSDOT’s performance journalism, is clearer and simpler, and therefore more effective than the top chart. In terms of industry-specific publications, there are three publications of import, all under- taken as NCHRP- and/or AASHTO-related projects. Two of these projects (the Communicating Performance and Vizguide websites) have been incorporated into the AASHTO Transportation Performance Management Portal, shown in Figure 7. The website includes the latest documents, videos, tools, trainings, and events for the TPM community. The earliest of these industry-specific studies was initialized in 2015 with support from the AASHTO Standing Committee on Performance Management and developed through NCHRP Project 20-24(93)B(02). The final results are a published report titled Communicating Perfor- mance Management—State DOTs Continuing to “Tell Their Story” (Spy Pond Partners, LLC and Sharp & Company 2015). The published report defines the overall purpose of the study and web application as follows: One product of this research, conducted through NCHRP Project 20-24(93)B(02), is a website that collects examples of noteworthy communications products and provides tools to help you support your agency’s performance management communication and reporting. You can use the site to discover exam- ples of noteworthy performance management communications and to access selected guidance for practi- tioners. The site has three core functions. The functions are to 1. Nominate noteworthy examples. 2. Browse communications products. 3. Explore communications scenarios. (Spy Pond Partners, LLC and Sharp & Company 2015) Figure 7. An example from the AASHTO Transportation Performance Management Portal (Source: AASHTO n.d.).

Literature Review 17   The Communicating Performance website provides a number of communications scenarios, also provided in outline form in the published report, for which they provide recommended guidance. The scenarios represented are • Telling the story, • Reporting progress, • Putting performance in perspective, • Educating the public, • Facing extreme weather, • Funding change, and • Opening for business. Clicking on any one of these scenarios then leads the user to a series of websites providing increasingly detailed recommended guidance based on the evaluation of existing practice as determined by the research conducted for the 2015 project. However, it is significant to note that the guidance provided for most of the scenarios is an identical six-step process, as shown in Figure 8. Step 1 is defined as “Learn,” and addresses the importance of collecting and evaluat- ing data and determining the most important message being told by the data. Step 2 is labeled “Plan,” and includes subjects such as defining an intended audience and establishing a concept that will most resonate with that audience. Steps 3 through 6, “Sketch,” “Create,” “Share,” and “Evaluate,” all emphasize the creative process in brainstorming and creating a visualization that Figure 8. Six steps shown from Communicating Performance (Source: AASHTO n.d.).

18 Visualization of Highway Performance Measures best meets the vision established by the concept selected in Step 2 and then determining the methods by which the visualization will be shared with the intended audience. While most of this particular information is included in the published report, the extended value of the project rests in the ongoing collection of resources by the published website. Each scenario also provides a set of links to real-life examples of visualizations of that type of data. The website provides the option to browse communications resources. This option allows users to search for real-life online examples of visualizations that match criteria that they select. These criteria are broken down, allowing the user to select which category best describes their intended audience, which category best describes the type of message they are trying to convey, and which category best describes the organization or individual that is the source of the message (or messenger). The search engine then provides a list of online resources, or examples, of the types of visualizations currently in use by transportation agencies that best align with the selected criteria. (The numbers in parentheses in Table 1 represent the number of examples in each category available through the website.) While this report and website are useful for locating real-life examples of what is currently being done, they fall short of establishing anything like best practices or comprehensive guid- ance on how to create the visualizations in terms of details of effective design process or strategy, on how to determine the intended audience, or on what tools are available to assist in the creation and dissemination of such visualizations. The next significant industry-specific publication is NCHRP Project 08-36 Task 128, which resulted in the 2017 web-only document, Data Visualization Methods for Transportation Agencies and a companion website, commonly referred to as Vizguide (see Figure 9). The report and the website contain much of the same information in a much more comprehensive guidebook- style publication. The report is only 36 pages, making it a quick and useful tool for practitioners who are looking for a simple overview of main concepts and perhaps an answer to the ques- tion, “Where do I start?” This report addresses common chart types, how to select an intended audience, how to analyze data for visualization, strategy (what medium to use, how to determine a “story” and tailor it to desired audience level), and available tools and includes a style guide (design principles, color, and font). For example, one of the questions the Vizguide publications assert as significant is “Are you and your data telling the same story?” The authors elaborate on the intent behind this question by explaining, “Your analytical and aesthetic decisions should reflect the nature of your data- set. Explore how much data you have, how many ways it can vary, and your need to illustrate uncertainty” (Cambridge Systematics, Inc. 2015). Audience DOT Leadership (19) DOT Personnel (20) Elected Officials (28) Media (21) Peer-to-Peer (7) Planning Partners (4) Public (100) Technical (13) U.S. DOT (1) Message Call to Action (15) Tough Choices (10) It’s complicated (9) I Can Explain (8) Case for Funding (32) We've Got This (30) Lessons Learned: Communicating Performance (2) Building Trust (15) We're Accountable (43) Messenger Agency-Wide (37) DOT Communications (15) DOT Leadership (9) DOT Partner (7) DOT PR (15) DOT Program Manager (46) Elected Officials (8) Outside Partner/Independent Voice (11) Technical (1) Table 1. Communicating Performance examples.

Figure 9. Vizguide (Source: Cambridge Systematics, Inc. 2015).

20 Visualization of Highway Performance Measures The Vizguide publications assert the complexity of the need for determining a strategy in approaching the design of any data visualization. They posit that it is not just a matter of selecting the appropriate type of chart or graph, “but also how you customize your charts and illustrations to reflect your intent, your audience, and the elements of your data.” They go on to suggest that the essential tasks when choosing a strategy include • Selecting a chart type or types, • Selecting a medium, • Differentiating your data points, and • Ensuring that your visualization is useful, clear, and memorable for your audience. These publications support the benefits of using a storytelling approach, particularly in terms of the frequent necessity of DOTs to communicate transportation-industry-specific data to those outside of the industry. Transportation planning is a field and an industry built for visualization. Information of relevance to planners can be readily illustrated, be it the design alternatives for a project, traffic flow in the peak hour, bicycle mode share, or color-of-money. Transportation professionals must also frequently com- municate plans, objectives, and justifications to lay stakeholders and a public in which “everyone who drives thinks they’re a traffic engineer.” (Higgins et al. 2017) The Vizguide publications make recommendations on how to translate data into effective visualizations that tell a story that resonates with the intended audience. One of the integral elements of this guidance is a style guide that is organized based on what Vizguide asserts are three key design principles: Keep it simple, Make it clear; and Be consistent. The documents summarize these concepts as follows: • Keep it simple: Visualizations should convey only the essential elements of the concept, keep text to a minimum, and be easily understood; • Make it clear: To help guide the eye, establish anchors in the visual. Choose fonts that are easy to read. Choose a readable font size and increase it for key statements to make them stand out. Use overlays to continue building on a visual and create emphasis through differentiation of format (e.g., position, color, shape, size, and existence [ . . . ]) and font; and • Be consistent: Once you decide on a style (color scheme, fonts, etc.), stick with it. The audience will know what to expect. (Higgins et al. 2017)

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Visualizations are tools for analyzing, reporting, and communicating the complexities of a transportation system and for synthesizing these intricacies into presentations that can be easily understood.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 584: Visualization of Highway Performance Measures documents current practices and methods used by state departments of transportation (DOTs) for visualizing highway performance measures and their use of visualization techniques for communication and decision support.

Supplemental to the publication is a Presentation of Visualization Examples.

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