What is a road centerline?

Road centerlines are vector line data that represent the geographic center of road rights-of-way on transportation networks. Road centerlines can be developed through a variety of techniques, including GPS data collection and digitization of roads on aerial photographs. Road centerlines can be used to encode road characteristics, including road name, road width, pavement type/conditions, number of travel lanes, travel directions, bridge weight limits, address ranges, speed limit, etc.
The extensive attribute data stored with road centerlines facilitate their use in GIS in a wide variety of applications. Examples include emergency dispatch, vehicle routing, address matching, road maintenance, and transportation modeling. In addition, road centerline data provide the foundation for car navigation systems.
Road centerline data are often collected/disseminated by local governments or state GIS clearinghouses. In addition, there are several private sector firms that maintain and sell road centerline files, including TeleAtlas and NAVTEQ.