The document discusses the I-95 Corridor Coalition GIS Project, which created a consolidated multi-state road network database by integrating individual state road centerline databases along the I-95 corridor. Significant challenges included differences in data quality and attributes between states. While useful for initial analysis, regularly updating the integrated database is difficult. Future efforts may be improved by starting with a commercial network or focusing only on core attributes.

1. March
11
Transportation for the Nation
Case Study – I-95 Corridor:
I-95 Corridor Coalition GIS Project
TFTN Strategic Plan Case Study

2. Overview
In support of the I-95 Corridor Coalition, Cambridge Systematics is coordinating
the development of a Corridor-wide information system that consolidates
existing state roadway network databases into a single multi-state roadway
network to guide regional transportation planning and emergency
management 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 of
Columbia, who are members of the I-95 Corridor Coalition. The individual state
roadway databases are ‘stitched together’ at the state borders to form a
topologically integrated network that can be used both for network analysis
and for overlaying other data of interest, such as crashes, traffic, roadway
conditions, and planned improvements. The consolidated road network also
includes a set of core attributes that are common across all states.
Project Background
Interstate 95 (I-95) is the main north-south Interstate highway on the eastern
coast of the United States, along the Atlantic seaboard. It is 1,925 miles long
from Houlton, Maine;—the border crossing with Canada—to Miami, Florida. It
passes through 15 states—Maine, New Hampshire, Massachusetts, Rhode
Island, Connecticut, New York, Pennsylvania, New Jersey, Maryland, Delaware,
Virginia, North Carolina, South Carolina, Georgia, and Florida—and the
outskirts of the District of Columbia.
The I-95 Corridor Coalition is a partnership of 16 state DOTs—the 15 mentioned
previously, plus Vermont, regional and local transportation agencies, toll
authorities, and related organizations, including public safety, port, transit, and
rail and other transportation organizations along the U.S. coast, with affiliate
members in Canada; it is neither a governmental entity nor an interstate
compact, but it provides an ongoing forum for interstate collaboration on
transportation and commerce.
Geographically, the I-95 Corridor traverses three traditional U.S. geographic
regions—New England, the Mid-Atlantic, and the Southeast.
The chain of expanding cities and roughly adjacent metropolitan areas
intersecting the Corridor has resulted in three socio-economic ‘megaregions,’
as defined by the Regional Plan Association (RPA), including the Northeast, the
Piedmont Atlantic, and Florida.

3. In terms of overall population density, approximately three times denser than
the U.S. average, the I-95 Corridor is comparable to Western Europe; it also
includes some of the oldest infrastructure in the U.S., and produces high
economic output as a whole.
The common concerns, functional interests, and geographic adjacency of the
state DOTs and other member agencies in the I-95 Corridor Coalition demand
a super-regional transportation systems perspective for improved modal
integration, coordinated policy, planning, and investment decision-making.
Lessons Learned and Challenges
There is a difference between integrating data for display and producing a
useful network. Integration issues included feature resolution, topology,
attributes, and attribute domains. For example, only two or three states had a
roadway centerline database with good network topology. To produce a
Corridor-wide road network that would be useful for network analysis, gaps
and overshoots in the road geometry had to be corrected to yield clean and
correct topological connections, which then needed to be verified and
validated.
Edge-matching across the states was not as big a problem as reconciling the
quality and consistency of the contents of the original datasets, which makes
updates and maintenance very challenging, especially for repeatable
dataset 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 route
number, significantly improves the percentage of correct matches.
A methodology is needed for managing road segment IDs (e.g., you can add
new IDs when splitting or adding road segments, and retire the old ones, or
find 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 their
geospatial datasets.

4. Conclusions
Many variations in data contents and consistency for road datasets were
encountered from state-to-state; but generally, useful and reasonably
accurate road features were available to produce a public domain road
network 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 down
commercial roadway centerline network as a framework, thereby relieving
integration requirements, and improving the consistency and convenience of
updates; the issue would be ensuring public domain accessibility, with no
license restrictions to inhibit use.
A “minimalist view” of needs for TFTN emerged from this project; i.e., you need
the following:
o Good centerline geometry for all roads, including local roads
o 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):

5. Sources: Dr. Bruce Spear, Cambridge Systematics; I-95 Corridor Coalition
Website ( 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” (Cambridge
Systematics, Dec. 2008); the Integrated Corridor Analysis Tool (ICAT) "WebCAT"
site, which provides an interactive GIS map display of the Coalition roadway
database 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-95
roadway network, at ftp://ftp.camsys.com/clientsupport/ICAT/site/index.htm;
Regional Plan Association website (http://www.rpa.org)