PRINCIPAL INVESTIGATORS

Marshall Thompson (1-40A(01))   Ernest Barenberg (1-40A(02))   Stephen Brown (1-40A(03))   Lynne Irwin (1-40A(04))

BACKGROUND

At the request of the AASHTO Joint Task Force on Pavements (JTFP), NCHRP initiated Project 1-37A in 1996 to develop a guide for the design of new and rehabilitated pavement structures. In contrast to the current AASHTO Guide for Design of Pavement Structures, the guide recommended in 2004 by the Project 1-37A research team is based on mechanistic-empirical (M-E) principles; provides a uniform basis for the design of flexible, rigid, and composite pavements; and employs common design parameters for traffic, subgrade, environment, and reliability.

A key component of the JTFP's plan for implementation and adoption of the M-E pavement design guide and software is an independent, third-party review to test the design guide's underlying assumptions, evaluate its engineering reasonableness and design reliability, and identify opportunities for its implementation in day-to-day design production work.

OBJECTIVE:

Conduct an independent engineering review of the mechanistic-empirical pavement design guide and software developed in NCHRP Project 1-37A.

Accomplishment of the project objective will require the following tasks:

TASKS

Task 1. Plan and conduct an independent engineering review of the mechanistic-empirical pavement design guide developed in NCHRP Project 1-37A, with specific emphasis on its use for the design of: (1) new flexible pavements, (2) new rigid pavements, and (3) composite pavements, design reliability, and a summary final report. In planning the review, make use, insofar as possible, of existing data and results from completed or ongoing studies.

In the review, address, at a minimum, the following requirements: (1) an assessment of the reasonability, soundness, and completeness of the guide's supporting engineering concepts and its process and procedures; (2) an appraisal of the consistency and sensitivity of results for new flexible, rigid, or composite pavement designs; (3) an evaluation of the design reliability methodology used in the guide; (4) an analysis of whether the distress models in the guide can be calibrated to match the predicted performance of select pavement structures with their known historical performance; (5) an assessment of the clarity, ease of use, capabilities, speed, and stability of the design software; (6) availability, clarity, and completeness of the necessary test protocols; (7) a review of the completeness with which the final design guide and software address the review comments of the NCHRP 1-37A panel and the JTFP; and (8) an assessment of opportunities for agency implementation of the design guide and software in routine, day-to-day design production work.

Task 2. Identify opportunities in the conceptual operation and structure of the design process, including the use of the environmental model outputs, to decrease the overall runtime of the software.

Task 3. Meet with the NCHRP project panel at beginning and the midpoint of the review to present an update on progress, key issues, principal findings, and recommendations.

Task4. Prepare a final report that presents key findings and recommendations, identifies specific deficiencies and errors in the design guide and software, and suggests corrective actions, including short-term research activities.

PRODUCT AVAILABILITY: The project final report is available as NCHRP Research Results Digest 307: Independent Review of the Mechanistic-Empirical Pavement Design Guide and Software.