Alligator cracking

is a type of distress that is generally caused by inadequate base support or brittle asphalt surface. Since cracks allow surface water to enter the subgrade and further destroy the stability of the subgrade, sealing should be accomplished as soon as practical. When cracking has progressed to the extent that failure of the roadway surface is imminent, repairs should be made as soon as possible. The alligator cracked surface material approaching failure will normally have to be removed and replaced with asphalt patching material. Where the base is unstable or wet, the base material will need to be removed replaced or stabilized.

Corrugations

are deviations of the pavement surface from its original cross section and are generally caused by excessive bitumen, improper aggregate gradation in the pavement, insufficient compaction of the mix or low interparticle friction to a degree that causes an unstable pavement with low resistance to traffic loads. Grooving, rutting, and shoving will also occur where the pavement is unstable. These distresses cause considerable annoyance to motorists. Repairs should be made as soon as practical when severe corrugations are evident. Repairs will normally involve removing the corrugated material and replacing it with new asphalt concrete.

Cracks

are considered significant when the pavement is cracked to the extent that water or foreign material can cause structural damage. At this point, cracks should be sealed as soon as practical. Efforts should be made to avoid a buildup of crack sealing material.

Edge cracking

frequently happens on narrow pavements at the same time drop-offs occur. This distress can be started by shrinkage of the asphalt at the edge of the pavement or shrinkage cracks in the base or subgrade. Edge loads tend to cause failure of this type by breaking off the pavement edge.

Failures and potholes

are subject to rapid enlargement and may result in considerable pavement loss and objectionable ride and may affect vehicle control. Failures and potholes should be repaired as soon as possible after they are observed or reported. In inclement weather, temporary repairs should be made and permanent repairs scheduled.

Pavement edge drop-offs

frequently occur on narrow pavement or pavement without paved shoulders where the wheels of vehicle frequently traverse off the pavement. New overlay may also leave a drop-off. When drop-offs get deep enough to cause hazards, repairs should be made as soon as possible. Pavement edge repairs are made by two accepted methods:

One method is to bring the natural material from the shoulder or the embankment material up to the level of the pavement surface edge.
The second method is to bring in asphalt or other material and add it to the edge of the pavement to remove the drop-off.

Raveling

is the progressive failure of the binder and loss of aggregate from the surface by weathering and/or traffic abrasion. When surface raveling begins to impair safety and/or extensive pavement loss is imminent, corrective action should be taken as soon as practical. Less critical raveling should be scheduled for correction on a priority basis.

Rutting

occurs when wheel track depressions have the undesirable effect of trapping water and may make vehicle control difficult. Corrections to the depressions should be made as soon as possible wherever ruts are determined to be a safety problem.

Slippery pavement

is the surface texture of bituminous pavement that is subject to adverse change as a result of aging, excessive asphalt, wearing, etc. Continuous surveillance of pavement texture should be made with particular attention being given to pavements that become slippery. Obvious slippery areas should be corrected as soon as practical to the extent feasible under the prevailing conditions. When additional corrective action is necessary, it should be scheduled and initiated promptly.

Waves, sags, and humps

are surface defects that often result in poor ride quality, and excessive impact loading of bridges and slabs, and may also make vehicle control difficult. Typical causes are fill settlement, unstable cuts, expansive soils and embankment shear failures. This type of defect may not cause any problem at low speeds but would be objectionable or intolerable at high speeds. Corrections to the surface should be made as soon as practical when ride quality is objectionable.