Load estimates should be based on representative current vehicle classification and truck weight data and anticipated growth in heavy truck volumes and weights. Accurate cumulative load (normally expressed as 18 kip equivalent single axle loads or ESALs) estimates are extremely important to pavement structural design.Pavement designers should work closely with the SHA component responsible for traffic volume, classification, and truck weight data required for pavement design. Highway agencies should pay particular attention to the following items in designing pavements.

To promote consistency in application of mechanistic-related design procedures, the Office of Pavement Technology will participate with the Resource Centers and Division Offices in reviewing and discussing these procedures with the State during their development. The FHWA encourages the development of mechanistic pavement design procedures.

If the reviews show that the SHAs have and are following an acceptable pavement design process, routine pavement design reviews of individual projects will not be required. As part of the review, FHWA field offices will sample a sufficient number of projects to determine that the pavement design process is being followed and the process provides reasonable engineering results.

Consistent with FHWA's operational philosophy on process review/product evaluation (PR/PE) attached to Executive Director Carlson's November 12, 1991, memorandum, the FHWA field offices can conduct periodic reviews of the SHA's pavement design process.

FHWA Evaluation of Pavement Design Procedures.

The SHA may use the design procedures outlined in the 'AASHTO Guide for Design of Pavement Structures,' or it may use other pavement design procedures that, based on past performance or research, are expected to produce satisfactory pavement designs.

Instead, each State Highway Agency (SHA) is expected to use a design procedure that is appropriate for its conditions.

General Pavement Design Considerations (23 CFR 626) Title 23 CFR 626 establishes the following requirement: 'Pavements shall be designed to accommodate current and predicted traffic needs in a safe, durable, and cost-effective manner.' The regulations do not specify the procedures to be followed to meet this requirement.

See Order 1321.1C FHWA Directives Management Formerly Federal-aid Policy Guide Non-Regulatory Supplement NS 23 CFR, Part 626,

Flexible pavement design aashto