March 11Transportation for the NationCase Study – I-95 Corridor:I-95 Corridor Coalition GIS ProjectTFTN Strategic Plan Case Study
OverviewIn support of the I-95 Corridor Coalition, Cambridge Systematics is coordinatingthe development of a Corridor-wide information system that consolidatesexisting state roadway network databases into a single multi-state roadwaynetwork to guide regional transportation planning and emergencymanagement efforts. This work includes the Integrated Corridor Analysis Tool(ICAT).The consolidated road network is comprised of the ‘best publicly-available’road centerline databases from each of the 16 states and the District ofColumbia, who are members of the I-95 Corridor Coalition. The individual stateroadway databases are ‘stitched together’ at the state borders to form atopologically integrated network that can be used both for network analysisand for overlaying other data of interest, such as crashes, traffic, roadwayconditions, and planned improvements. The consolidated road network alsoincludes a set of core attributes that are common across all states.Project BackgroundInterstate 95 (I-95) is the main north-south Interstate highway on the easterncoast of the United States, along the Atlantic seaboard. It is 1,925 miles longfrom Houlton, Maine;—the border crossing with Canada—to Miami, Florida. Itpasses through 15 states—Maine, New Hampshire, Massachusetts, RhodeIsland, Connecticut, New York, Pennsylvania, New Jersey, Maryland, Delaware,Virginia, North Carolina, South Carolina, Georgia, and Florida—and theoutskirts of the District of Columbia.The I-95 Corridor Coalition is a partnership of 16 state DOTs—the 15 mentionedpreviously, plus Vermont, regional and local transportation agencies, tollauthorities, and related organizations, including public safety, port, transit, andrail and other transportation organizations along the U.S. coast, with affiliatemembers in Canada; it is neither a governmental entity nor an interstatecompact, but it provides an ongoing forum for interstate collaboration ontransportation and commerce.Geographically, the I-95 Corridor traverses three traditional U.S. geographicregions—New England, the Mid-Atlantic, and the Southeast.The chain of expanding cities and roughly adjacent metropolitan areasintersecting the Corridor has resulted in three socio-economic ‘megaregions,’as defined by the Regional Plan Association (RPA), including the Northeast, thePiedmont Atlantic, and Florida.
In terms of overall population density, approximately three times denser thanthe U.S. average, the I-95 Corridor is comparable to Western Europe; it alsoincludes some of the oldest infrastructure in the U.S., and produces higheconomic output as a whole.The common concerns, functional interests, and geographic adjacency of thestate DOTs and other member agencies in the I-95 Corridor Coalition demanda super-regional transportation systems perspective for improved modalintegration, coordinated policy, planning, and investment decision-making.Lessons Learned and ChallengesThere is a difference between integrating data for display and producing auseful network. Integration issues included feature resolution, topology,attributes, and attribute domains. For example, only two or three states had aroadway centerline database with good network topology. To produce aCorridor-wide road network that would be useful for network analysis, gapsand overshoots in the road geometry had to be corrected to yield clean andcorrect topological connections, which then needed to be verified andvalidated.Edge-matching across the states was not as big a problem as reconciling thequality and consistency of the contents of the original datasets, which makesupdates and maintenance very challenging, especially for repeatabledataset Extraction, Transformation, and Loading (ETL) and conflation, i.e.,fusion of features and attributes into an integrated dataset.Geographic conflation, i.e., matching lines, alone is generally not sufficient;conflation combined with basic roadway identifiers, e.g., road name or routenumber, significantly improves the percentage of correct matches.A methodology is needed for managing road segment IDs (e.g., you can addnew IDs when splitting or adding road segments, and retire the old ones, orfind a way to have persistent IDs (which can be a challenge)).Most of the state DOTs are only interested in a subset of all roads.Most of the state DOTs were using FGDC metadata to document theirgeospatial datasets.
ConclusionsMany variations in data contents and consistency for road datasets wereencountered from state-to-state; but generally, useful and reasonablyaccurate road features were available to produce a public domain roadnetwork for the Corridor, for the purposes of the project.Doing this once is the “easy part” (easy being a relative term); the “hard part”is doing this on a regular, repeatable basis to keep the road network updated.If a “do over” was contemplated, it might be easier to use a stripped downcommercial roadway centerline network as a framework, thereby relievingintegration requirements, and improving the consistency and convenience ofupdates; the issue would be ensuring public domain accessibility, with nolicense restrictions to inhibit use.A “minimalist view” of needs for TFTN emerged from this project; i.e., you needthe following:o Good centerline geometry for all roads, including local roadso Good feature resolution (i.e., travel way representation, not lane level)o Good positional accuracy (i.e. 1-5m)o Basic network topology (i.e., road segments connect at at-grade intersections and freeway ramps, but not at grade-separated overpasses/underpasses.)o Basic attributes (i.e., road names and numbered routes; addresses and linear referencing could also be included, or reserved for value-added)o Regular and predictable updates A potential I-95 graphic to use follows (c/o Cambridge Systematics):
Sources: Dr. Bruce Spear, Cambridge Systematics; I-95 Corridor CoalitionWebsite ( http://www.i95coalition.org ); documents from the website,including, “I-95 Vision Study Task 5 – Policy Implications” (I-95 Corridor Coalition,July 2008), “A 2040 Vision for the I-95 Coalition Region” (CambridgeSystematics, Dec. 2008); the Integrated Corridor Analysis Tool (ICAT) "WebCAT"site, which provides an interactive GIS map display of the Coalition roadwaydatabase and thematic maps, at http://ags.camsys.com/webcat/; the ICAT"DataCAT" site, which allows users to download the integrated road network,individual state networks, and other geospatial data that are linked to the I-95roadway network, at ftp://ftp.camsys.com/clientsupport/ICAT/site/index.htm;Regional Plan Association website (http://www.rpa.org)