The project provided three practical and useful pavement design products: (1) a catalog of current state pavement design features, (2) a catalog of recommended (good practice) pavement design features, and (3) a prototype knowledge-based expert system.

The objective of the design process is to identify pavement structures that will provide acceptable performance and economy over the intended design life. A rational pavement design must consider the effects of roadbed soil, climate, traffic loading, construction materials, and other design details and features on pavement performance and life-cycle costs. In spite of similarities in environment, traffic, and roadbed soil within and among some states, practices for design and construction vary widely. To help guide highway authorities in selecting suitable and reliable designs, there was a need to compile a catalog of current state design features for flexible and rigid pavements and also to develop a catalog for pavement design that identifies recommended design structures and features for these pavements. Supplementing these catalogs with a microcomputer-oriented, knowledge-based expert system would further enhance their use and facilitate their updating.

NCHRP Research Results Digest 227, "Systems for Design of Highway Pavements," provides a summary of the work performed under this project. The project's final report; including the catalog of current state pavement design features, the catalog of recommended (good practice) pavement design features, and the prototype knowledge-based expert system; has been reproduced on a CD-ROM which is available for purchase.