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Publication Number: FHWA-HRT-11-064
Date: November 2011

 

Guide on The Consistent Application of Traffic Analysis Tools and Methods

CHAPTER 7. VISUALIZATION AND COMMUNICATION AIDS

Throughout the course of the traffic analysis sequence and life cycle of project delivery, effective communication between members of the analysis team and others contributing to the project can eliminate significant sources of inconsistency. Communicating results to those beyond the study team must also be done in an effective manner.

This chapter presents an overview on communicating technical information, challenges to the effective use of analysis, general guidance on communicating technical information, data presentation techniques, guidance on writing technical reports, advice on preparing technical presentations, information on using software displays and animations, and a discussion of presenting and explaining inconsistent results.

Technical presentations can take the form of presenting to a small department-level working group, to a larger group within the organization, to an interagency group of transportation professionals, or to public stakeholders and decisionmakers.

TIPS FOR PRESENTATIONS OF TECHNICAL DATA

A guiding principle for preparing presentations should be that they do not have to be original but they must be accurate. Be sure to use analytical data to convey points. For clarity, remember that although non-technical decisionmakers may be busy, they are not stupid. Examining how newspapers like the New York Times or Wall Street Journal report complex technical information to a wide audience can serve as a guide for developing presentation material. Edward Tufte presents the following tips for presentations.(10)

Be able to describe the problem, its relevance, and the solution. Prepare at least one paragraph devoted to each of these in advance of the presentation.

Prepare and distribute a handout containing the essential details of what the presentation will cover. That way, the most important elements are there, the audience all will have received it in the handout, and if the presentation derails, the important topics are still covered. A preferred format for the handout is an 11-by-17-inch sheet folded in half, prepared in booklet form. This makes for a nicely structured summary of the presentation.

The audience should know beforehand what is going to be presented. Then, they can evaluate how the verbal and visual evidence supports the argument. Near the beginning of the presentation, tell the audience the following details:

If a clear statement of the problem cannot be formulated, the content of the presentation will be deficient. Give the audience many chances to get the point. Repeated variations on the same theme will often clarify and develop an idea. Additionally, characterizing and respecting the audience helps the presenter avoid underestimating or pandering to the audience.

To explain complex ideas or data, use the method of PGP: particular, general, particular. For example, to help the audience understand a multivariate table of data, briefly introduce the table and point to a particular number and say what it means. Then, step back and describe the general architecture of the table. Finally, reinforce it all with a second particular, explaining what another number means. The two particulars can be selected to make a substantive point as well as to explain the data arrangement. With PGP, the argument is more credible, as there is more than a single anecdote to accompany the general theory. An example would include presenting vehicle delays, volume-to-saturation flow rate ratios, and queuing at a signalized intersection. Start by discussing the specific information for one of the critical movements (e.g., a left-turn movement) by highlighting the delays and how the queuing results compare to the available turn pocket storage length. Next, discuss the general outline of the presentation of the data by explaining the locations of these data across the board for all movements. Then, point out another specific movement, perhaps another critical movement on the cross street.

Seek to maximize the rate of information transfer to the audience. Rather than just reading aloud from images projected from a computer, give everyone in the audience one or more pieces of paper packed with material related to the presentation. Handouts can show pictures, diagrams, data tables, research methods, references, or the complete text of the paper outlined in the talk. Unlike projected images, permanent and portable paper has credibility. This also has consistency benefits by conveying more detail of the analysis to others who may employ it as part of their future project work.

Analyze the details of the presentation. Then, master those details by practice, practice, practice. Good teachers know the value of preparation and practice.

Plan arrival and departure so as to make a difference. Show up early, and finish early. By arriving early the physical elements of the presentation can be prepared and presenters can adjust to the specifics of the room. Greet people as they arrive. Finishing early will rarely, if ever, garner any complaints from your audience.

Test for the integrity of the content being presented. Ask the following questions:

Following these tips for presentations will help communicate analysis results in a more effective manner and promote consistency.

USING SOFTWARE DISPLAYS AND ANIMATION

Visual displays from transportation analysis software can be used to convey key information about the project's characteristics and analysis results. Transportation analysis software tools output many different types of reports, graphical displays, and animation videos. These outputs vary by classification, purpose, and sophistication level of the software program. These values can be compared among the various study alternatives.

Travel Demand Models

Graphical plotting options of travel demand models are useful for presenting analysis results. These can take the form of plots displaying network characteristics such as number of lanes and volume-delay functions, volume plots, thematic maps, zonal pie charts, isochrones, scatter plots, and matrix visualizations. Through these types of presentations, as well as tabular output, travel demand models can be used to display the following:

Traffic Signal Optimization Tools

Analysis results from traffic signal optimization tools can be displayed using graphical outputs in the form of time-space diagrams depicting cycle lengths, splits, coordination, and offsets.

Simulation

Microsimulation software tools include animation, video representations of the traffic operations being modeled. These videos are visually powerful presentation tools that can be saved in a file format that does not require the underlying simulation software when replaying them (generally in the form of .avi files). These files can then be embedded within Microsoft PowerPoint® presentations for ease of playback and portability during a presentation.

In previous projects, analysts found that displaying visual presentations of their simulations using two-dimensional and three-dimensional .avi files before submitting the written technical report was a good step. The presentation showed that the model reflected real-world conditions of queuing and hot spots.

OVERVIEW ON COMMUNICATING TECHNICAL INFORMATION

Traffic analyses result in a plethora of output data. Deciphering which outputs are important for evaluating a project's purpose and which are not, as well as evaluating which resulting values of these outputs are reasonable or not, are critical roles of analysts and project managers.

The analyst is charged with proactively providing useful information on a timely basis. Analysts can help support projects by using an array of communications tools. The effective communication of technical information can also encourage two-way communication with stakeholders, providing an additional level of error-checking and interpretation of results to the traffic analysis process. Moreover, effective communication also fosters teamwork and goodwill because keeping an audience well-informed reduces negative interaction.

It is not common for analysts' training to focus on the skills that support high-quality presentations. Although agencies tend to have some standardization in the type and content of studies and reports required through the project life cycle, the focus on presentation can be uneven. Some agencies provide templates for report organization or tables of contents, but even where templates are provided, guidance for adapting templates to specific study objectives is sparse.

During the planning stages of analysis, when the audience may include political decisionmakers, it is apparent that more attention is paid to communication. In the course of design, environmental analysis, and operational assessments, effective communication can eliminate considerable sources of inconsistency. Effective presentation and communication within and between organizations is regarded as a distinct discipline and in other professional fields (particularly the private sector) managers are expected to have some proficiency in these areas.

CHALLENGES TO THE EFFECTIVE USE OF ANALYSIS

Analysis tools provide data in a wide variety of formats, some of which are tremendously voluminous. Requirements to postprocess some of the output adds even more. The challenges inherent in presenting results coherently and documenting the analysis are complicated by the fact that the technical background of the audience, particularly, decisionmakers or other readers, may be limited.

Work that is not successfully communicated loses a considerable amount of its value. The fact that analysts and many project managers are not trained to present information can lead to perceived inconsistencies among readers and to real inconsistencies as analysis is passed along through the project life cycle.

Traffic analysis tools generate an array of outputs that can be used by analysts in reporting or communicating the results of their analyses, but several hindrances can appear based on differences in definitions, file formats, and organization of the outputs. This can lead to misinterpretation of analysis findings. Likewise, the value of the analysis process is demonstrated by the relevance the findings have for informing decisionmaking. Communicating findings effectively is, therefore, essential in order for the traffic analysis results to accurately influence policy decisions.

Guidance for communicating technical information, writing technical reports, and preparing technical presentations is provided in the following sections.

GENERAL GUIDANCE ON COMMUNICATING ANALYSIS

Determining the best tools and measures for decisionmaking depends on the purpose of the analysis. Decisionmaking audiences can generally be divided into three broad categories: public organizations, agency management, and agency technical staff. Public organizations include entities such as city planning commissions, city councils, community groups, and other boards. Agency management includes individuals at higher levels who may or may not be well-versed in technical analysis procedures. Technical staff includes engineering or planning analysts and project managers charged with performing or directly managing traffic analysis. Additionally, members of the general public are an audience to whom technical information needs to be communicated.

The results of traffic analyses can be difficult for decisionmakers to interpret unless the data, findings, and analytic interpretations are carefully organized and presented. In general, the results should be presented as simply as possible. This might include using a limited set of performance measures and providing the data in an aggregate form. However, while simplicity has its merits, the analyst should be careful when striving to simplify the message not to lose the ability to communicate the underlying variations and factors that generated the results.(8)

Decisionmakers who are not analytically oriented often prefer to have a single number or letter represent a condition. It is generally not effective to provide representatives of the public with a large set of differing measures or with a frequency distribution for a specific performance measure. If the analyst has several measures available, it is preferable to select the one that best fits the situation and to keep the others in reserve until needed.(8)

Decisionmakers who represent the public usually prefer measures that their constituents can understand. When selecting the measures to present, it is important for the analyst to recognize the orientation of the decisionmaker and the context in which the decision will be made. In general, these measures can be differentiated as system-user or system-manager oriented. When making a presentation to technical members of a public agency such as highway engineers and planners, it might be necessary to use more than one performance measure, especially when providing both the system-user and system-manager perspectives.(8)

Principles of Presenting Analysis Results

Simple and direct graphics reflect the fundamental principles of effective communication of results. Tufte describes eight of these principles.(10)

Principle 1: Comparisons

The first principle for analysis and presentation of data is to show comparisons, contrasts, and differences. Answer the question "compared with what?" (Such as the "do nothing" case.) Whether evaluating changes over space or time, adjusting and controlling for variables, designing experiments, or doing just about any kind of evidence-based reasoning, the essential point is to make intelligent and appropriate comparisons. In traffic analysis, comparisons can be made between "project" and "no-project" scenarios, between various analysis forecast years, and between peak and off-peak conditions, among others. It is important to present these comparisons consistently. The benefit of consistency is that decisions can then be made based on logical criteria that are evident and replicable.

Principle 2: Causality, Structure, Explanation

Fundamental intellectual tasks should be addressed in the analysis of the output results. The second principle for the analysis and presentation of data is to show causality, explanation, and systematic structure. Describe the causal variables at play and how they affect outcomes. In traffic analysis, describe how variations in traffic volumes affect operating conditions, how capacity improvements affect travel speeds and delays or induce latent demand, or how freeway ramp metering or traffic signal optimization affects delays and throughput, among others. Having a consistent structure for presenting the analysis will more effectively establish the relationship between key variables and major findings. The audience will find it easier to understand the implications of the analysis, and recommendations will be more persuasive.

Principle 3: Multivariate (Complex) Analysis

Most topics of inquiry are multivariate (involving three or more causal variables). Transportation analysis is no exception. Describing and displaying the interplay and effects of the many variables in your analysis can yield a more thorough reasoning and understanding of the results. If relationships are not explained, the audience may get lost and fail to understand the interactions between important concepts. Be clear, but avoid oversimplifying the problems when presenting results. Make sure to explain the effects of complexity and how they were accounted for.

Principle 4: Integration of Evidence (Tell a Complete, Coherent, and Consistent Story)

Words, numbers, pictures, diagrams, graphics, charts, and tables belong together. For example, good maps routinely integrate words, numbers, artwork, grids, and measurement scales. The fourth principle for the analysis and presentation of data is to completely integrate words, numbers, images, and diagrams. Tables of data can be thought of as paragraphs of numbers and can be tightly integrated with the text for the convenience of reading rather than segregated in an appendix. Annotate images and tables in your presentations with explanations of what is going on. When presenting text and data analysis, this integration can be accomplished in layers. At first, the data can be presented as standalone points to cleanly and clearly show the data. Then, layering techniques can be employed to add the other information to the presentation.

Principle 5: Clear and Complete Documentation

The fifth principle for the analysis and presentation of data is to thoroughly describe the analysis results. Documentation is essential for quality control in such displays. Thorough documentation is a good sign that a report was constructed with some care and craft. Documentation should be integrated with presentation materials using footnotes in reports and legends in figures. Authorship credit should also be included. Displays should name their data sources. Viewers should be informed about the scales of measurements on data graphics. This requires referencing any policies that establish and justify an advocacy position on the part of report authors. Communicating the policy and other background related to qualitative or subjective statements allows the audience and other analysts to refer to that background when similar situations occur, which promotes consistency. Point out potential conflicts of interest. Thorough documentation allows more effective review. Provide a detailed title, indicate authors and sponsors, document the data sources, show complete measurement scales, and point out relevant issues.

Principle 6: Content Counts Most of All

Good knowledge of the content and a deep caring about the substance of the analysis promotes excellent analytical documentation and communication. Analytical presentations ultimately stand or fall on the quality, relevance, and integrity of their content. The most effective way to improve a presentation is to get better content. Formatting gimmicks cannot salvage failed content. The most important question when constructing analytical presentations should be "What is this display is supposed to communicate?" Ensure that the main ideas are communicated without superfluous distractions. Distractions lead to inconsistencies. Bad decisions are made when the audience is distracted from the main point.

The preceding principles are implemented in the creation of data presentations by the analyst for inclusion in written reports and presentations of technical information.

DATA PRESENTATION TECHNIQUES

Transportation reports and presentations typically convey significant amounts of data representing a variety of information from the input stage through the results stage of analysis, as well as result summaries. The data are often represented in illustrations such as tables, figures, and diagrams, which are efficient and powerful ways to present the results. It is crucial, however, that these elements convey their intended messages. Properly designed illustrations succinctly and poignantly present key elements of the study in a manner that is both approachable and enlightening to the reader. Poorly designed illustrations can fail to communicate the relevant information and can confuse and distort the data or results. Table 8 presents an overview of the guiding principles for selecting techniques to display data.

Table 8. Quick guide to data presentation techniques.

Use

To Show

Principle

Table in text

Summary of output data central to theme of report

1, 2, 3, 4, 5, and 6

Table in appendix

Summary of research materials serving as background to analysis

4 and 5

Bar charts

Comparison of the value of different items at specific points in time or at specific physical locations

1, 4, 5, and 6

Line graphs

Display of time series and trend data

1, 4, 5, and 6

XY graphs

Display of relationships among two or more series of data points where the intent is to show general relationships via clouds of points rather than explicit lines

1, 2, 4, 5, and 6

Pie charts

Relative distribution of each value to the whole of a single series of data

1, 4, 5, and 6

Area graphs

Display of data showing parts or shares and the whole and how they change over time

1, 4, 5, and 6

Thematic maps

Locations of a variable over a geographical area

1, 4, 5, and 6

Flow charts

Depiction of processes or procedures, denote certain types of actions, activities, or decisions in the process

1, 2, 4, 5, and 6

Progress charts

Time schedule for a study or project

4, 5, and 6

Diagrams and maps

Depiction the project’s study area, its physical features, and a host of project-related information

1, 2, 3, 4, 5, and 6

When creating illustrations, consider the following:

Bar Chart

A bar chart uses vertical and horizontal bars to represent each value in a series. They are typically used to compare the value of different items at specific points in time or at specific physical locations.

Line Graph

Line graphs connect each value in a series with a line. Line graphs are used to display time series and trend data. Care needs to be given to be certain that non-continuous data do not imply continuity in the data.

XY Graphs

XY graphs display relationships among two or more series of data points where the intent is to show general relationships via clouds of points rather than explicit lines. Plots may display only data points, a line without the data points, or a best-fit line overlaid on the points.

Pie Charts

Pie charts show the relative distribution of each value to the whole of a single series of data. They work well when there are a limited number of items making up the pie. Bar charts work better when there are too many items to display well in pie form. Pie charts are best when the desire is to show the proportionate or percentage contribution of each item toward the total. They help the reader quickly separate the major items from the minor items.

Area Graph

Area graphs present each series as an area of the chart. These areas can be filled in using a variety of coloring, gradations, or hatchings. Data series are stacked vertically, rather than shown side-by-side. This works best for displaying data showing parts or shares and the whole. This also shows changes over time.

Thematic Maps

Thematic maps show the locations of a variable over a geographical area. An example would be a State map depicting vehicle registrations per 1,000 population within each county, with county boundary lines.

Flow Charts

Flow charts depict processes or procedures. Triangles, boxes, ovals, circles, and other shapes are used to denote certain types of actions, activities, or decisions in the process. Lines with arrows show possible actions. An example is a flow chart displaying the decision-making process for which class of software tools is most appropriate for a particular type of project analysis.

Progress Charts

Progress charts depict the time schedule for a study or project. The time span of the project is displayed on the horizontal axis in appropriate increments (weeks, months, quarters, etc.). Each task is displayed as a horizontal bar spanning the duration of time for which the task should take place. These charts are also known as Gantt charts. They are used in scoping as project planning tools as well as employed to check the progress of the various tasks as the project proceeds.

Diagrams and Maps

Diagrams or maps depict the project's study area, its physical features, and a host of project-related information. Study area limits, roadway geometry and lane striping, traffic volume data, and intersection control type are examples of the information that can be displayed in such figures.

RESOURCES FOR FURTHER READING

There are many useful resources for presenting technical analyses and writing technical reports. The following is a partial list:

 

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