Various structural elements associated with the Road dataset. The following are ‘crossings’ being a point feature class representing structures that facilitate the crossing of a road or railway over, under or through another feature. Road Bridge: a structure erected over a depression or obstacle to carry a road. Road Tunnel: an underground or underwater road passage. Floodway: a section of road specifically designed to allow periodic or permanent subjection to water inundation. Road Culvert: a masonry conduit which serves as a channel-crossing for water or a transport network beneath a road. Ford: a shallow or flat portion of a bed of a watercourse where a crossing may be affected. Note the ‘ontype’ attributes of road-segment features mentioned above which have an obvious topological link to these features.