The Arizona Department of Transportation (ADOT) implemented an incentive/disincentive asphalt concrete (AC) smoothness specification in 1990. Since then hundreds of projects have been tested for smoothness. These projects have included a wide variety of layer combinations of one or more of the following: overlay, remove, replace, and finishing course. The number of projects and variation in design allows comparisons of the smoothness results for different design strategies as well as trends in smoothness results over time. In addition to the tests on the final surface, many projects were also tested on intermediate lift surfaces.

A statistical analysis of the smoothness data is conducted to study the smoothness distribution and to compare the pavement smoothness of different categories. The smoothness correlation between various layers is also studied. The economic benefits of the implementation of ADOT's smoothness specification are evaluated. The results of this study can be useful in establishing target levels for newly implemented or revised pavement smoothness specifications.