Key:mtb:scale:itrs:exposure
 mtb:scale:itrs:exposure
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| Description |
|---|
| Consequences of a fall off a mountain bike trail section, rated with the International Trail Rating System (ITRS), 1 to 4. |
| Group: bicycles |
| Used on these elements |
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| Requires |
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| Useful combination |
| Status: in use |
| Tools for this tag |
mtb:scale:itrs:exposure=* records how bad the consequences of a fall off a section of mountain bike trail are, as rated with the International Trail Rating System (ITRS), from 1 to 4. It rates the terrain beside the trail, not the difficulty of riding it.
On a way, the value is the rating of the most exposed spot along that way. On a node of the way, it marks one such exposed section and gives its rating.
ITRS rates mountain bike trails and routes on four aspects: technical difficulty, endurance, exposure, and wilderness. Trained ITRS trail raters survey and rate a trail as a series of segments that each has its own ratings for technical difficulty and exposure.
(Endurance and wilderness describe a whole route, a relation, rather than a section of trail, and are not covered here. In the future these could be covered by mtb:scale:itrs:endurance=* and/or mtb:scale:itrs:wilderness=* applied to relations.)
Two keys represent the per-segment ITRS ratings in OSM: this one, and mtb:scale:itrs:technical_difficulty=* for how much riding skill a section demands.
ITRS ratings are separate from mtb:scale=* and mtb:scale:imba=*. They use different criteria and one should not be derived from another. It is possible for a way to be tagged with ratings from all three systems.
| mtb:scale:itrs:* | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| technical_difficulty |  Beginner |
 Intermediate |
 Advanced |
 Expert |
 Extreme |
| exposure |  Normal injury risk |
 High risk of serious injury |
 Life threatening consequences |
 Fatal consequences |
(none) |
Applies to
highway=pathhighway=cyclewayhighway=track- Nodes of those ways, to mark where an exposed section is
Other highway=* values may be used if their primary designation differs, such as highway=footway or highway=bridleway.
ITRS does not present a rating for paved or surfaced roads; this key is not used on them.
How to map
Tag the ways that the rated segments run along. Ratings may change part-way along a trail, so a way may need to be split where the rated sections end.
- Only tag ratings that come from an ITRS survey. Don't estimate an ITRS value from riding a trail or from another scale.
- This key and
mtb:scale:itrs:technical_difficulty=*are independent. A section can have one without the other. - Leave existing
mtb:scale=*,mtb:scale:uphill=*, andmtb:scale:imba=*tags alone.
Notes
- The most exposed section of a segment sets the rating for the whole segment (
segment_max_exposurein ITRS GeoJSON), so a short exposed section can give a long segment a high value. To show the specific exposed section, also tag a node of the way at the exposed section with the same key and its rating. ITRS GeoJSON records show these as exposure points (point_exposure_rating). - A node with this key should be a node of the trail way, placed on the exposed section, and not a node shared with another trail (it would be unclear which trail the rating belongs to).
- A segment with a rating of 0 in the ITRS data was not rated for that aspect. Leave the key off rather than tagging 0.
- A suggested changeset source is
source=ITRS trail rating survey, with the ITRS version and survey date where known.
Values
A segment's exposure describes the consequences of falling off the trail, not the difficulty of riding it. The same values apply on ways and on nodes.
| Tag | Symbol | ITRS level | Colour | Consequences of a fall |
|---|---|---|---|---|
mtb:scale:itrs:exposure=1 |
 |
Normal injury risk | Green | No worse than a fall on the trail itself. |
mtb:scale:itrs:exposure=2 |
 |
High risk of serious injury | Blue | Serious injury is likely, eg: a steep slope where a fall can still be stopped, or a drop of about 2 m beside the trail. |
mtb:scale:itrs:exposure=3 |
|
Life threatening consequences | Red | A fall could be fatal, though there is some chance to stop, eg: steep ground above a drop, or a drop of about 4 m beside the trail. |
mtb:scale:itrs:exposure=4 |
 |
Fatal consequences | Black | A fall is fatal: a vertical drop directly beside the trail, with no chance to stop. |
See ITRS: Exposure for the full criteria.
Rendering
ITRS publishes official colours for each level and asks that maps showing ITRS ratings use them. Graphic details are available in the Graphics Toolbox available for download from ITRS.
- trailmaps.app-map-generator reads
mtb:scale:itrs:technical_difficulty=*andmtb:scale:itrs:exposure=*on maps set to the ITRS scale. It draws the ITRS symbols, colours trails by technical difficulty or exposure, and shows both ratings in the trail popup.
Usage
The Copper Harbor Trails Club in Michigan, USA, has begun rating its trail system with ITRS, including new ITRS signage. See Copper Harbor, Updated Wayfinding, and the International Trail Rating System (ITRS) (Copper Harbor Trails Club, 2025-Dec-04).
Licensing
The ITRS – International Trail Rating System is used with permission from Mischa Crumbach and Edoardo Melchiori. The ITRS symbols on this page come from the ITRS graphic resources and are used under the ITRS licensing conditions (CC BY-NC-ND 4.0 with a CC+ agreement).
See also
mtb:scale:itrs:technical_difficulty=*: the ITRS technical difficulty rating for the same trail sections- ITRS: International Trail Rating System
mtb:scale=*: a classification scheme for the difficulty of trails for mountain bikingmtb:scale:uphill=*mtb:scale:imba=*: the IMBA Trail Difficulty Rating System, for purpose-built trails- Mountain biking
sac_scale=*: a classification scheme for hiking trails