1. March
11
Transportation for the Nation
Case Study – Virginia:
Northern Virginia Regional Routable Centerline Project
TFTN Strategic Plan Case Study

2. Overview:
The Data Collection and Analysis project consisted of five jurisdictions in
the Northern Virginia area, which are all Public Safety Answering Points
(PSAP), as well as the Virginia Information Technology Agency (VITA) and
the Virginia Department of Transportation (VDOT), in active collaboration
to develop a routable centerline data set and standard usable by
computer-aided dispatch (CAD) systems. The updated standard will be
applied to the Virginia Geographic Information Network (VGIN) state
road centerline file format (RCL) and be employed in future projects.
The participating jurisdictions are Fairfax County as the project lead,
Arlington County, Alexandria City, Loudoun County, and Prince William
County. The interior jurisdictions to these larger areas, such as Fairfax City,
Falls Church City, Town of Herndon, etc., will be included in the project
wherever possible. This business process is in place—see Figure below—
and is used effectively to get basic street centerline information for any
other jurisdiction. It is expected that this project will improve on the existing
business process and the data supplied. The project has been funded by
the 911 Fund, which helps pay for the PSAP Grant, and various other state
projects including the state orthophotography road centerline project.

3. The purpose of this project is to enhance VGIN RCL to create a regional
street centerline capable of supporting routing, geocoding, and persistent
updates to local 911 map systems. It will allow for design, development,
updating, and population of an enhanced RCL which will fully support
each individual CAD system for data outside their own jurisdiction, while
not forcing them to change the data model currently used in CAD. Fairfax
County recently went live with a new CAD system with AVL, and has
gained a full understanding of what is needed in GIS to support routing. In
a perfect world, Fairfax County would be square and all routing could be
conducted within its own jurisdiction. Then, there would be no need to
route outside of its borders. However, since that is not the case, the
county is dependent upon data outside of its borders.
Project Background:
The goal of this effort is to generate and use a persistent set of unique IDs
that will provide a way to track and identify changes at the centerline
level. As part of the maintenance process, VGIN collects and distributes
data from local jurisdictions based on a FIPS code—jurisdiction
designation—for each arc in the data set.
For the current use of VGIN data, it makes no difference which jurisdiction
an arc straddling two jurisdictions originates from. However, once those
local governments try to use these data in a CAD system, it makes an
enormous difference. Consider the example of Rynex Rd. on the border of
Fairfax County and Alexandria City. A portion of this street has Fairfax
addresses on both sides; a portion has Fairfax addresses on one side and
Alexandria addresses on the other. Both jurisdictions need a
representation as part of their database to support a CAD system. Using
the current process, only one would be imported into the VGIN data,
causing problems with future updates. This project will develop a
technical solution to this problem, as well as a methodology and best
practices guide that other jurisdictions can use to resolve the same issue.
For data outside of Fairfax, the team used the State RCL data. The process
of incorporating this data was not intended for a single use due to issues
with this data and the amount of work required making it work with
existing CAD systems.
Lessons Learned and Challenges:
The data needed to be edge-matched which means that the State data
streets didn’t match up with the data where it should have, so each street

4. along the borders needed to be realigned to match so that there is
connectivity.
Throughout the process, there were additional issues with the way dual
roadways were represented—Fairfax maintains dual centerlines where
others maintain a single centerline, so those needed to be matched up at
the borders.
There were also inconsistent naming standards, which posed a problem
when considering the round trip of the data. One-way information was
absent from the dataset and because of this, at one point during testing,
the team was able to identify a route that went the wrong way up a
ramp. Speed limits were missing on the state data, and proper routing
without speed limits is not possible. There were overlapping addresses
and/or gaps at the borders, which could result in two possibilities for one
address, and some addresses not being recorded. These issues, in
addition to the Fairfax experience, are all justification for a regional
routable centerline.

5. Conclusions:
The VGIN RCL project is considered a huge local success because of the
communication and handshaking that occurs between the state and the
state DOT. This is an ongoing project that will eventually have a seamless
flow from participating cities and counties up to the state and then back
again to complete the round trip. Additional work on the project includes
the development of maintenance tools and the integration of regional
data into CAD systems.
Sources: Brendon Ford (GIS Applications & Systems Administrator Fairfax
County Department of Information Technology), Brian Wooley (Street
Centerline Coordinator, Loudon County), Mike Fauss (Manager of the
Land Records Maintenance Division, Loudon County), Dan Widner
(Coordinator, Virginia Geographic Information Network, Virginia
Information Technologies Agency (VITA)), Larry Stipek (Director of the
Office and Mapping and Geographic Information, Loudon County)