Key:modifier
 modifier
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| Description |
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designation that distinguishes a special route from its parent route, identified by an auxiliary plate above or below the route marker 
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| Group: properties |
| Used on these elements |
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| Requires |
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| Useful combination |
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| See also |
| Status: de facto |
| Tools for this tag |
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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=*.
History
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. OsmAnd considers modifier=* to some extent when displaying shields,[1] but most shield-capable renderers do not.[2]
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
References
- ↑ “MapRenderingTypesEncoder.java”. osmandapp/OsmAnd-tools. December 13, 2022. Retrieved April 6, 2023.
- ↑ “Supported Routes”. OpenStreetMap Shield Rendering. July 20, 2012. Archived from the original on May 15, 2021. Retrieved September 7, 2020.