Learn about the various zone types.
State, county and city zone types
These types of zones are identified through tags built into our road segments themselves. Road segments are exclusive to state, county and cities, meaning no segments belong to more than one state, county or city. If one would cross the boundary, it should be cut into two different segments for each of the geographies in which it resides. When using these geographies as zones, segments are pulled based on the tags that associate it to whichever state, county and city to which it belongs.
Other zone types
For all other zone types, we calculate which road segments belong to a zone by determining if any point in the segment resides within the zone. If any point of the segment is within the zone boundaries, then that segment is considered part of that zone. This process is more complex, as it requires looking at all points in a segment to determine if any of them are within the zone boundaries.
Metrics impact
Due to efficiency optimization for both our scenarios, the results can be slightly different when pulling segments from states, counties, and cities compared to other zone types. When pulling segments and comparing between the smaller and larger zones, the sum of the segments may be different than a collection of different zones that make the same geography as the larger zone, such as pulling for all CTRs in a county instead of using the county zone itself.