text: The present invention relates to methods for representing roads as data in a database and more particularly, the present invention relates to methods for representing road lanes in a database used for vehicle driver assistance systems.
  Vehicle driver assistance systems, such as systems for obstacle warning and avoidance, lane departure warning, collision warning and avoidance, adaptive cruise control, adaptive transmission operation, automatic headlight aiming, and so on, have been developed to improve the safety and convenience of vehicle operation. These systems include technologies that augment a driver's ability to operate a vehicle safely and efficiently. Some of these systems include equipment that senses features around the vehicle. In addition, some of these systems use data that models the road network upon which the vehicle is traveling. Based on the sensed features and the model of the road network, the driver assistance and safety systems may provide warnings or otherwise modify operation of the vehicle to improve safety or convenience.
  Data representations of the road network have also been used for various other purposes. For example, data representations of the road network are used in vehicle navigation systems to provide navigation-related features, such as route calculation, route guidance, map display and destination selection. In some databases used by navigation systems, each road segment is represented by one or more data records or entities. Associated with each data record or entity are attributes that describe various features of the represented road segment. Some of the features of a road segment that are represented by such data records include the location of the road segment, the locations of road intersections, the name of the road segment, the speed limit (or speed category) along the road segment, the number of lanes along the road segment, any highway designations of the road segment, the type of road surface (e.g., paved, unpaved, gravel), the presence of any lane dividers, etc.
  The ways that roads are represented in databases used in navigation systems are useful. However, the ways that roads are represented in databases used for navigation purposes may not be suitable for driver assistance and safety systems. For example, for navigation purposes, it is important to have data that indicate the speed limits along roads, the names of roads, the address ranges along road segments, and how much time it might take to cross a road intersection. For navigation purposes, the exact path that a vehicle takes along a road segment is not necessarily important unless the vehicle is approaching an upcoming maneuver. However, for driver assistance systems, such as obstacle avoidance or warning systems, the paths that vehicles take along a road segment may be needed to provide a warning or take another action.
  Accordingly, it is an objective to provide a data model for roads, and in particular for lanes along roads, that can be used by driver assistance systems.
  It is another objective to provide a data model for road lanes that is compatible with various uses of the data.