Classifies roads by their importance and capacity in the transportation network. Used for filtering traffic data display based on road significance.
Road hierarchy (from highest to lowest):
motorway / motorway_link - High-capacity highways with restricted accesstrunk / trunk_link - Major inter-city roadsprimary / primary_link - Primary through routessecondary / secondary_link - Secondary through routestertiary / tertiary_link - Connecting roadsstreet - Local streets (see StreetRoadSubCategory)service - Service roads (see ServiceRoadSubCategory)track - Unpaved or agricultural tracks
Road hierarchy category type.