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Showcasing Visualization Tools in Congestion Management

Data Types Used in Visualizations

Visualizations are tools to summarize an extensive amount of data into a more easily comprehensible set of information. This data can come from multiple sources. Data may be directly collected by the MPO utilizing in-house staff and resources or temporary personnel, or through consultants. For instance, many MPOs conduct travel time studies, traffic counts, or intersection studies. Data may also be gathered by the MPO from external, secondary sources that collect data for a different main purpose. For instance, data may include transit operations data from transit providers or archived ITS data from traffic flow detectors used by transportation operations organizations. Some of these sources may actually be more useful, easier to gather, more detailed, or less costly than directly-collected data would be.

It is also important to note another distinction in the information used in creating visualizations. Most MPOs use observed data while some also use simulated or forecasted information. Observed data may not always be available for the desired analysis but there may be similar or related types of information from the travel demand modeling system, which can lead an MPO to rely on modeled information instead of observed data. When the CMP is dealing with future scenarios, modeling of information is necessary. When dealing with recent or past conditions, observed data is often more accepted by decision makers. Many of the visualization tools can be used either with observed data or modeled information, but it is important to be aware that the public or decision-makers may mistake modeled data for visualizations of "observed" data.

At many MPOs the collection and gathering of data lies at the heart of CMP activities. These 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. As noted above, MPOs also tend to use results from modeling simulations as part of the CMP, due in part to the fact that historically, the communication of the results of forecasts of future congestion conditions has been a major part of the activities of MPOs. There can sometimes be a very large amount of such modeled information, depending on the complexity of the model and the number of scenarios tested using the model. One major challenge for MPOs is how to organize, interpret, and use the large volumes of data and processed information that are available for use. Visualization can be an effective tool for doing this, and then for presenting the most pertinent information to the public. This section focuses on the different data types that are used in CMP visualizations.

Types of data and use of data

There are many types of data that can be used in visualizations as part of the CMP process. Data types are often differentiated or categorized according to the source or underlying nature of the data. The following list is not exhaustive, but includes several common types of data that are used in CMP-related visualizations by MPOs.

Data types are often differentiated or categorized according to the underlying nature of the data. One such important aspect of each of these data types to make note of is the distinction between spatial data (what happens at a given location) and temporal data (what happens at a given time or over a period of time). It is generally understood that congestion of component parts of our transportation systems is often very site- or "spatial-specific" as well as time- or "temporal-specific". Visualization can be an effective means of integrating spatially- and temporally-based data features into a single more understandable display of congestion.

Micro-simulation models used by some MPOs in their analyses of congestion conditions can generate animated simulations that represent the spatial-temporal extent of the build-up and then the dispersion of congestion over an area or along a corridor, as well as the concurrent duration of the congested conditions over time. Static displays, such as time-distance congestion contour displays based upon observed data have long been used in operational planning and are beginning to be used by MPOs in CMP activities.

Updated: 07/25/2011
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