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Flexible Pavement Design FAQ

Note: Both the Long Life Pavement Design FAQ are being developed.

How do we design Flexible Pavement?

Answer: The current Department standard for both rehabilitation and new flexible pavement design is an empirical method based on relationships developed from several test tracks and experience with actual pavement performance. Refer to HDM Topic 633 for new design procedures and HDM Topic 635 for rehabilitation design procedures.

Is there any software that we can use for Flexible Pavement design calculations?

Answer: Yes. The Office of Pavement Engineering developed the CalFP v.1.1 program for new flexible pavement design calculations and the CalAC v.3.2 for flexible pavement rehabilitation design calculations.

How does Life Cycle Cost Analysis (LCCA) relate to Flexible Pavement design?

Answer: LCCA requires analysis of designs with varying design lives, strategies, and pavement materials. For more information, refer to Section 2.1 in the LCCA Procedures Manual (PDF).

What is the procedure for designing a recycled flexible pavement structure?

Answer: In-Place Recycling (PDR, FDR-FA, FDR-C, and Pulverization) may be used on projects. Approval to use the non-standard special provisions (nSSPs) for Partial Depth Recycling (PDR) is obtained from the Office of Asphalt Pavements.

What is Mechanistic-Empirical Design?

Answer: Mechanistic-Empirical design methodology combines engineering knowledge of the mechanical interaction of pavement materials with empirical research to model the response of proposed pavement designs to variables including traffic loading, climate, and material composition.

Is Mechanistic-Empirical (M-E) design used by the Department for designing Flexible Pavements?

Answer: The Department currently uses an empirical method for flexible pavement structure designs (see Question 1). Mechanistic-Empirical design methodology may be used on projects with approval from the Office of Pavement Engineering in the Division of Pavement (see HDM Index 606.2 (PDF)). Reasons for using Mechanistic-Empirical design might include longer design life or a traffic index (TI) greater than 15.