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Public-images-osm logo.svg modifier
Business alternate plate.svg
designation that distinguishes a special route from its parent route, identified by an auxiliary plate above or below the route marker Edit or translate this description.
Group: Properties
Used on these elements
should not be used on nodesshould not be used on waysshould not be used on areasmay be used on relations
Useful combination
See also
Status: de facto

This key is used to indicate the designation that distinguishes a special route from its parent route. The modifier is typically identified by an auxiliary plate above or below a route marker. In an MUTCD-compliant country, such as the United States, a special route is identified by the combination of its network=*, ref=*, and modifier=*.


This key was part of the U.S. mapping community's original consensus about route relation tagging circa 2009, as seen on pages such as Interstate Highway relations:

  • Distinct network=* tag for a route that has a shield distinct from its parent route, for example:
  • modifier=* for a route that is signposted using the parent route's unchanged shield plus an auxiliary plate, for example:

Unfortunately, any data consumer that doesn't understand modifier=* would end up incorrectly handling some routes, such as by losing the distinction between a truck route and its parent route. This phenomenon is known as a "troll tag".

Over the years, modifier=* has remained in use but has become less important, as mappers have tended to always add to network=*, even when there is only an auxiliary plate and no distinction in the route shield. No renderer currently uses modifier=* to affect the displayed shield.[1]

Other usage

modifier=left and modifier=right have also been used many times in an import of road_marking=solid_stop_lines in several U.S. cities. The meaning of these tags is unclear, but it is probably a nonstandard way to indicate the side of the road.

See also


  1. “Supported Routes”. OpenStreetMap Shield Rendering. July 20, 2012. Archived from the original on May 15, 2021. Retrieved September 7, 2020.