A rut is a surface depression in the wheel path. Pavement uplift may occur along the sides of the rut: however, in many instances ruts are noticeable only after a rainfall, when the wheel paths are filled with water. Rutting stems from a permanent deformation in any of the pavement layers or subgrade, usually caused by consolidation or lateral movement of the materials due to traffic loads. Significant rutting can lead to major structural failure of the pavement.

Severity Distress Example Description
Low Overview photo of a taxiway pavement with visible low-severity rutting in one wheelpath.            The rutting is visible because there is standing water in the wheelpath. Mean rut depth criteria: 1/4 to 1/2 in (6 to 13 mm).
Medium Close-up photo showing an area of medium rutting.  The rutting is visible in the photo as           two deeper longitudinal ruts. Mean rut depth criteria: > 1/2 to 1 in (> 13 to 25 mm).
High Overview photo of a pavement with a visible area of high-severity rutting.            A 6-ft (2-m) long piece of wood has been placed across the rut to show the depth of the rut. Mean rut depth criteria: > 1 in (> 25 mm).