T F T N S t r a t e g i c P l a n C a s e S t u d y

Case Study – Virginia: Northern Virginia Regional Routable Centerline Project

March   11

Transportation for the Nation

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.

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

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.

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)