- A rut is a surface depression in the wheel paths.
- Rutting stems from a permanent deformation in any of the pavement layers or sub-grade.
- Depressions are localized areas where the pavement surface is lower than the surrounding area but the transition is not abrupt enough to be considered a distortion.
- They are often referred to as bird baths.
| L, M, & H Severity Rutting & Depression | |
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| Low: About 3/4 in (18 mm) deep. | Medium: About 1 1/2 in (37 mm) deep. |
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| High. About 3 in (150 mm) deep. | |