Mechanistic–Empirical

Pavement Design Guide

A Manual of Practice

© 2008 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.

Preface | ii

prefAceThis document describes a pavement design methodology that is based on engineering mechanics and has been validated with extensive road test performance data. This methodology is termed mechanistic-empirical (M-E) pavement design, and it represents a major change from the pavement design methods in practice today.

From the early 1960s through 1993, all versions of the American Association for State Highway and Transportation Officials (AASHTO) Guide for Design of Pavement Structures were based on limited em-pirical performance equations developed at the AASHO Road Test in the late 1950s. The need for and benefits of a mechanistically based pavement design procedure were recognized when the 1986 AAS-HTO Guide for Design of Pavement Structures was adopted. To meet that need, the AASHTO Joint Task Force on Pavements, in cooperation with the National Cooperative Highway Research Program (NCHRP) and the Federal Highway Administration (FHWA), sponsored the development of an M-E pavement design procedure under NCHRP Project 1-37A.

A key goal of NCHRP Project 1-37A, Development of the 2002 Guide for Design of New and Rehabilitat-ed Pavement Structures: Phase II was the development of a design guide that utilized existing mechanis-tic-based models and data reflecting the current state-of-the-art in pavement design. This guide was to address all new (including lane reconstruction) and rehabilitation design issues, and provide an equitable design basis for all pavement types.

The Mechanistic-Empirical Pavement Design Guide (MEPDG), as it has now become known, was com-pleted in 2004 and released to the public for review and evaluation. A formal review of the products from NCHRP Project 1-37A was conducted by the NCHRP under Project 1-40A. This review has resulted in a number of improvements, many of which have been incorporated into the MEPDG under NCHRP Project 1-40D. Project 1-40D has resulted in Version 1.0 of the MEPDG software and an updated design guide document.

Version 1.0 of the software was submitted in April 2007 to the NCHRP, FHWA, and AASHTO for further consideration as an AASHTO provisional standard and currently efforts are underway on Version 2.0 of the software. Simultaneously, a group of state agencies, termed lead states, was formed to share knowledge regarding the MEPDG and to expedite its implementation. The lead states and other interested agencies have already begun implementation activities in terms of staff training, collection of input data (materials library, traffic library, etc.), acquiring of test equipment, and setting up field sec-tions for local calibration.

This manual presents the information necessary for pavement design engineers to begin to use the MEPDG design and analysis method. The FHWA has a web site for knowledge exchange for the MEPDG (http://knowledge.fhwa.dot.gov)

© 2008 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.

tABle of contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Purpose of Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Overview of the MEPDG Design Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. Referenced Documents and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Test Protocols and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2 Material Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3 Recommended Practices and Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 Referenced Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113. Significance and Use of the MEPDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.1 Performance Indicators Predicted by the MEPDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2 MEPDG General Design Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 New Flexible Pavement and HMA Overlay Design Strategies Applicable for Use with

the MEPDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 New Rigid Pavement, PCC Overlay, and Restoration of Rigid Pavement Design

Strategies Applicable for Use with the MEPDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.5 Design Features and Factors Not Included Within the MEPDG Process . . . . . . . . . . . . . . . 234. Terminology and Definition of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.1 General Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.2 Hierarchical Input Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.3 Truck Traffic Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.4 Smoothness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.5 Distress or Performance Indicator Terms—HMA-Surfaced Pavements . . . . . . . . . . . . . . . . . 31 4.6 Distress or Performance Indicator Terms—PCC-Surfaced Pavements . . . . . . . . . . . . . . . . . . 315. Performance Indicator Prediction Methodologies—An Overview . . . . . . . . . . . . . . . . . . . . . . . . 33 5.1 Calibration Factors Included in the MEPDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 5.2 Distress Prediction Equations for Flexible Pavements and HMA Overlays . . . . . . . . . . . . . . 34 5.3 Distress Prediction Equations for Rigid Pavements and PCC Overlays . . . . . . . . . . . . . . . . . 496. Hierarchical Input Levels—Deciding on the Input Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 6.1 Introduction to Hierarchical Input Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 6.2 Purpose of the Hierarchical Input Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 6.3 Selecting the Input Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687. General Project Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 7.1 Design/Analysis Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 7.2 Construction and Traffic Opening Dates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 718. Selecting Design Criteria and Reliability Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8.1 Recommended Design-Performance Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8.2 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 749. Determining Site Conditions and Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 9.1 Truck Traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 9.2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

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© 2008 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.

9.3 FoundationandSubgradeSoils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 9.4 ExistingPavements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8610.PavementEvaluationforRehabilitationDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 10.1 OverallConditionAssessmentandProblemDefinitionCategories. . . . . . . . . . . . . . . . . . . . . 87 10.2 DataCollectiontoDefineConditionAssessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 10.3 AnalysisofPavementEvaluationDataforRehabilitationDesignConsiderations. . . . . . . . 10411.DeterminationofMaterialPropertiesforNewPavingMaterials. . . . . . . . . . . . . . . . . . . . . . . . . 109 11.1 MaterialInputsandtheHierarchicalInputConcept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 11.2 HMAMixtures;IncludingSMA,Asphalt-TreatedorStabilizedBaseLayers,and

AsphaltPermeable-TreatedBaseLayers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 11.3 PCCMixtures,LeanConcrete,andCement-TreatedBaseLayers. . . . . . . . . . . . . . . . . . . . . 117 11.4 ChemicallyStabilizedMaterials;IncludingLeanConcreteandCement-TreatedBaseLayer. . 117 11.5 UnboundAggregateBaseMaterialsandEngineeredEmbankments. . . . . . . . . . . . . . . . . . . 12412.PavementDesignStrategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 12.1 NewFlexiblePavementDesignStrategies—DevelopingtheInitialTrialDesign . . . . . . . . 129 12.2 NewRigidPavementDesignStrategies—DevelopingtheInitialTrialDesign . . . . . . . . . . 13613.RehabilitationDesignStrategies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 13.1 GeneralOverviewofRehabilitationDesignUsingtheMEPDG. . . . . . . . . . . . . . . . . . . . . . 143 13.2 RehabilitationDesignwithHMAOverlays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 13.3 RehabilitationDesignwithPCCOverlays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16414. InterpretationandAnalysisoftheResultsoftheTrialDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.1 SummaryofInputsforTrialDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.2 ReliabilityofTrialDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.3 SupplementalInformation(LayerModulus,TruckApplications,andOtherFactors). . . . 182 14.4 PredictedPerformanceValues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.5 JudgingtheAcceptabilityoftheTrialDesign....................................... 185Appendix:GettingStartedwiththeMEPDG A.1 InstallingtheSoftware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 A.2 UninstallingtheSoftware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 A.3 RunningtheSoftware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190AbbreviationsAndTerms Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196Index Indexofwords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

iv | Mechanistic–Empirical Pavement Design Guide

© 2008 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.

444 North Capitol St. NWSuite 249Washington, DC 20001(202) 624-5800www.transportation.org

Publication Code: MEPDG-1ISBN: 978-1-56051-423-7