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A slipping pavement can result from a construction defect, an existing condition, or a design flaw. And whether the pavement defect is in a parking lot or a roadway intersection, the only effective repair is complete removal and replacement of the slip area. Therefore, prevention is always the best solution.

The pavement "tears" or "slips" if the tension caused by the traffic is stronger than the sum of the pavement's internal strength and the pavement's bond to the underlying layer. Analyzing these two components will help predict and eliminate slipping.

Why pavements slip

Heavy vehicles, including garbage trucks and delivery trucks, create much greater stress on the pavement, than lighter vehicles. A loaded tri-axle dump truck does the same damage to a pavement as 9,800 passenger cars. Therefore, heavy truck traffic is the most important factor in analyzing pavement deficiencies.

A rolling vehicle at a constant speed applies most of its stress vertically to the pavement, and vertical stress doesn't cause slippage. That's why you don't see much slippage in the middle of roads or highways. Slippage is most likely to occur at intersections and in parking lots where vehicles brake, accelerate, or turn sharply. These actions try to pull the pavement apart by applying lateral tension to the surface.

Asphalt is very strong in compression, but relatively weak in tension. Asphalt shares this common characteristic with concrete. (Concrete is about 10 times stronger under a compressive load, than under a tension load.)