Bumps and Sags

Bumps are small, localized, upward displacements of the pavement surface. They are different from shoves in that shoves are caused by unstable pavement. Bumps, on the other hand, can be caused by several factors, including buckling or bulging of underlying PCC slabs in AC overlay over PCC pavement, frost heave (ice, lens growth), or infiltration and buildup of material in a crack in combination with traffic loading (sometimes called “tenting”). Sags are small, abrupt, downward displacements of the pavement surface. If bumps appear in a pattern perpendicular to traffic flow and are spaced at less than 10 ft (3 m), the distress is called corrugation. Distortion and displacement that occur over large areas of the pavement surface, causing large or long dips, or both, in the pavement should be recorded as swelling.