Abstract:

Cambridge Systematics developed a tool to disaggregate and visualize freight flows to and from North Carolina using the Freight Analysis Framework Version 4 (FAF4) origin-destination commodity flow data. Through this process the origins and destinations in the FAF4 data were disaggregated from FAF Zones to U.S. Counties. FAF Zones are larger regions and can be metropolitan area determined regions; regions representing a State’s territory outside metropolitan regions; and regions identified as entire states, within which no FAF metropolitan regions exist. The disaggregation process requires the identification of the freight activity in a smaller geography (e.g. county) as a percentage of the freight activity in the region that contains that smaller geography (e.g. FAF Zone). The freight activity can be calculated using production and attraction equations of tonnage by commodity and explanatory variables such as the industry(s) that produce or attract those commodities. The disaggregation process is executed in specialized code and the disaggregated trip tables are generated for a specific study area, in this case North Carolina, where the Origins and Destinations in the state are at the county level and outside of the state are kept as FAF zones and for international flows are disaggregated to border crossings and port gateways. Using this methodology, a Tableau-based data visualization was then used to generate interactive “fact sheets” for each of North Carolina’s 100 counties, as well as national and international freight flows. The tool’s application in North Carolina allows—despite the number of FAF zones, counties, border crossing and port gateways—a manageably-sized database that can be used to visualize freight flows in a user-friendly, accessible format. Users can identify geographic freight flows and trends for dozens of freight categories, transport modes, commodity types, and trading partners, with data displayed in an easily-understood, annotated manner. The tool can be accessed here: https://public.tableau.com/profile/cambridge.systematics#!/vizhome/NorthCarolinaFreightFlowTool/Story1 The use of Tableau enabled rapid prototyping and development of a web-based tool on a limited budget, while remaining flexible enough to capture the nuanced and complex nature of the dataset. By relying on the combination of Microsoft Access and Tableau, the tool was made portable (i.e., required a minimum of setup), accessible (i.e., requires no licensing for access and minimal licensing for deployment), and easily updatable. The tool functions as a stand-alone component of a comprehensive long-range freight plan, providing an alternative to the creation of hundreds of static fact sheets and datasets. In general, use of data visualization in freight plans has served to augment executive summaries and public-facing handouts with a useful and efficient “get to the point” communication strategy useful at public meetings, on social media, and in presentations to stakeholders and decision makers. This tool is part of a larger initiative at Cambridge Systematics to create exciting and useful data products that communicate critical issues of transportation planning and modeling to clients and stakeholders alike.