The American Concrete Pavement Association (ACPA) publishes and distributes a design software program called Streetpave. The ACPA describes the program on the back of the software CD-ROM jacket as follows: “It includes an asphalt cross-section design process (based on the Asphalt Institute method) to create an equivalent asphalt design for the load carrying capacity requirement. … With one pavement design tool, you can design equivalent concrete and asphalt sections and evaluate the best possible solution(s) for your pavement needs.”
The Asphalt Institute provides a paper that will demonstrate how this claim of “equivalent” asphalt and concrete sections is undeniably false. Streetpave inappropriately reduces the single design modulus value for subgrade strength (input by the user) prior to running the asphalt design calculation. No similar reduction is performed with the concrete design. Thus, the asphalt section is based on a subgrade that is significantly weaker than the subgrade the concrete design is based on. The result is an asphalt section that is thicker than necessary, and thus more costly, making the falsely alleged “equivalent” concrete section look more attractive.
To understand how this manipulation of the AI method within Streetpave takes place, read either the full 11-page paper here or a 3-page summary article here.