Mechanistic-Empirical Design – AASHTO MEPDG This method is used by VDOT for higher-volume secondary roads, primary roads, and interstate highways. The most commonly used empirical pavement design method is the 1993 AASHTO Guide for Design of Pavement Structures. Specifically, it is not prudent to use an empirically derived relationship to describe phenomena that occur outside the range of the original data used to develop the relationship. Although the scientific basis for these relationships is not firmly established, they can be used with confidence as long as the limitations of such an approach are recognized. This means that the relationships between design inputs (e.g., loads, materials, layer configurations and environment) and pavement failure were determined using experience, experimentation or a combination of both. Many pavement structural design procedures use an empirical approach. Vaswani Design Guide for Subdivision and Secondary Roads in Virginiacan be found on the VDOT website.

Today, this method is still in use for low-volume secondary and subdivision roads. The Vaswani method was developed for use on all new asphalt pavement designs as well as overlay of asphalt pavements. Nari Vaswani, a researcher at the Virginia Highway and Transportation Research Council (today known as the Virginia Center for Transportation Innovation and Research), took the results of the AASHTO Road Test and developed a modified procedure known as the Vaswani method.

A recommendation from this national report was for transportation agencies to modify the design approach to local conditions and materials. In the early 1960’s, AASHTO (formerly AASHO) released a pavement design methodology based on the results of the national road test in Ottawa, Illinois. Empirical Design – Secondary and Sub-Division Roads (Vaswani Method) The principal methods of structural design in use today are (from simplest to most complex) empirical and mechanistic-empirical. Calculations are chiefly concerned with traffic loading stresses other environmentally related stresses (such as temperature) are accounted for in mix design asphalt binder selection. Structural design is mainly concerned with determining appropriate layer thickness and composition. This section is focused on the structural design of new pavement. This includes the surface course as well as any underlying base or subbase layers. The goal of structural design is to determine the number, material composition and thickness of the different layers within a pavement structure required to accommodate a given loading regime.

Pavement design aashto method