Transportation Infrastructure: Highway Pavement Design Guide Is Outdated

Published by the Government Accountability Office on 1997-11-21.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

                United States General Accounting Office

GAO             Report to the Secretary of

November 1997
                Highway Pavement
                Design Guide Is

      United States
GAO   General Accounting Office
      Washington, D.C. 20548

      Resources, Community, and
      Economic Development Division


      November 21, 1997

      The Honorable Rodney E. Slater
      The Secretary of Transportation

      Dear Mr. Secretary:

      The National Highway System encompasses about 155,000 miles of the
      nation’s most important interstate, arterial, and major highways and
      freeways, which represents about 4 percent of the nation’s approximately
      4 million miles of public roads. Billions of dollars have been spent to
      construct these roads and highways, and preserving and maintaining them
      is estimated to cost billions of dollars more each year. In 1995, the U.S.
      Department of Transportation (DOT) estimated that the average annual
      cost to maintain overall highway conditions and performance for this
      system through the year 2013 to be $44.8 billion.1

      An American Association of State Highway Officials2 road test conducted
      in 1959-60 to obtain pavement performance data showed—among other
      things—that heavy trucks cause more highway pavement damage than
      other vehicular traffic. On the basis of this test, the Association developed
      an initial pavement design guide in 1961, and it has been updated
      periodically since then. DOT’s Federal Highway Administration (FHWA)
      neither adopts the guide nor requires its use by states. Rather, FHWA—in its
      working relationship with states—requires that sound engineering and
      management principles and practices be used in the pavement design
      process. According to FHWA, one indication of this is the states’ use of
      guides and standards developed by a number of standard-setting industry
      organizations, including AASHTO.

      This report (1) describes the roles of FHWA and others in developing and
      updating the pavement design guide and (2) examines the use and
      potential of a computer analysis method known as the nonlinear 3
      Dimensional-Finite Element Method (3D-FEM)3 for improving the design and
      analysis of highway pavement structures.

        1995 Status of the Nation’s Surface Transportation System: Condition and Performance, DOT
      (Washington, D.C.: Oct. 27, 1995), pp. xix, 175.
      This organization has since become the American Association of State Highway and Transportation
      Officials, more commonly known as AASHTO.
        The nonlinear 3D-FEM method uses a set of computer programs to analyze engineering problems. It has
      been used for about 25 years for solving structural problems with complicated geometries, loadings,
      and material properties associated with aeronautical, biomedical, automotive, naval architecture,
      nuclear weaponry, off-shore drilling, piping, and seismic engineering.

      Page 1                                         GAO/RCED-98-9 Highway Pavement Design Guide

                   The Federal Highway Administration has worked cooperatively with the
Results in Brief   American Association of State Highway and Transportation Officials in
                   developing and updating the pavement design guide. The current guide is
                   slated to be updated by the year 2002 to better reflect the changing priority
                   of rehabilitating the nation’s highways rather than building new ones. In
                   contrast to the current guide that many transportation experts believe is
                   outdated, the new guide is expected to incorporate the use of analytical
                   methods to predict pavement performance under various loading and
                   climatic conditions. Sponsors believe that “a new design approach will
                   more realistically characterize existing highway pavements and improve
                   the reliability of designs.”

                   A promising analytical method to accurately predict pavement response is
                   the nonlinear 3 Dimensional-Finite Element Method. Only with accurate
                   response data can one reliably predict pavement performance. The use of
                   this method has the potential to improve the design of highway
                   pavements—which encompasses their safety, durability, and
                   cost-effectiveness—because values of stresses, strains, and deflections
                   (pavement response) can be calculated accurately from a variety of static,
                   impact, vibratory, and moving mixes of traffic loads. Several state
                   departments of transportation, academicians, and scientists have
                   pioneered the use of the nonlinear 3 Dimensional-Finite Element Method
                   and are using it to solve a variety of complex structural engineering
                   problems, including the design and analysis of highway pavement
                   structures. While this is a promising method for improving highway
                   pavement design and analysis, we could find no evidence that it is being
                   considered for inclusion in the current design guide update.

                   FHWA  is responsible for administering and overseeing various highway
Background         transportation programs, including the Federal-Aid Highway
                   Program—which provides financial assistance to the states for improving
                   the efficiency of highway and traffic operations. FHWA relies on AASHTO to
                   (1) provide technical guidance for the design, construction, and
                   maintenance of highways and other transportation facilities; (2) publish
                   manuals, guides, and specifications regarding design, safety, maintenance,
                   and materials; and (3) conduct planning for highways, bridges, and other
                   structures. Active membership in AASHTO is open to the state departments
                   of transportation of the United States, Puerto Rico, and the District of
                   Columbia. DOT is an active, albeit nonvoting, member. FHWA supports
                   AASHTO’s manuals, guides, and specifications, which the states can use in
                   designing and analyzing federally funded highway projects. In addition,

                   Page 2                              GAO/RCED-98-9 Highway Pavement Design Guide

                  states can use their own pavement design criteria and procedures for such
                  projects, which generally mirror what is in AASHTO’s pavement design

                  Currently, highway pavement design criteria and procedures are
Updating the      documented in AASHTO’s 1993 Guide For the Design of Pavement
Pavement Design   Structures. AASHTO’s Joint Task Force on Pavements is responsible for the
Guide             development and updating of the guide. The guide was first issued in 1961
                  and then updated in 1972, 1981, 1986, and 1993. Another update of the
                  guide is forthcoming. The task force’s efforts to update the guide are
                  overseen by a National Cooperative Highway Research Program (NCHRP)
                  project panel, which functions under the Transportation Research Board
                  (TRB) of the National Academy of Sciences’ National Research Council.

                  While constructing new highways was once the primary goal of state
                  transportation departments, the major emphasis in pavement design in the
                  1990s has progressed to rehabilitating existing highways. According to
                  NCHRP, the current guide does not reflect this shift in emphasis, and the
                  updated guide is the expected product of an NCHRP/TRB contract with an
                  engineering consulting firm that is expected to be awarded in the near
                  future. Under the contract, the guide would be updated by 2002. In
                  updating the guide, NCHRP intends to improve upon the outdated pavement
                  design procedures contained in the current guide.

                  The current design guide and its predecessors were largely based on
                  design equations empirically derived from the observations AASHTO’s
                  predecessor made during road performance tests completed in 1959-60.
                  Several transportation experts have criticized the empirical data thus
                  derived as outdated and inadequate for today’s highway system.4 5 In
                  addition, a March 1994 DOT Office of Inspector General report concluded
                  that the design guide was outdated and that pavement design information
                  it relied on could not be supported and validated with systematic
                  comparisons to actual experience or research.6 In contrast to the current
                  guide, which relied heavily on an empirical approach to derive its design

                    Kenneth A. Small, Clifford Winston, and Carol Evans, Road Work, The Brookings Institution
                  (Washington, D.C.: 1989), pp. 26-27.
                   Jerry J. Hajek, General Axle Load Equivalency Factors, Ontario Ministry of Transportation,
                  Downsview, Ontario, Canada, TRB, Transportation Research Record No. 1482 (Washington, D.C.:
                  Report on Audit of Cost Comparison of Asphalt Versus Concrete Pavement, DOT Office of Inspector
                  General, FHWA Region 4, Report Number R4, FH-4-008 (Mar. 30, 1994).

                  Page 3                                         GAO/RCED-98-9 Highway Pavement Design Guide

                       equations, the NCHRP contract to update the guide by 2002 calls for the use
                       of an approach that would more realistically characterize existing highway
                       pavement usage and improve the reliability of designs.

                       Under the first phase of the contract that ended in July 1997, Nichols
                       Consulting Engineers developed a detailed work plan for completing the
                       new pavement design guide. When the project manager resigned in
                       June 1997, NCHRP decided to rebid the contract. The NCHRP program officer
                       stated that he believes that the new guide will be completed as planned.

                       An existing method called nonlinear 3D-FEM has the potential to
An Existing Pavement   significantly improve the design and analysis of highway pavement
Design and Analysis    structures. A number of nonlinear 3D-FEM computer programs have been
Method Has the         available since the 1970s that can be used for solving complex structural
                       engineering problems, including designing safer, longer-lasting, more
Potential to Improve   cost-effective highway pavement structures.7 Nonlinear 3D-FEM is
Highways and Is        considered by many experts to be superior to current design and analysis
                       methods because values of stresses, strains, and pavement deflections can
Being Used by Others   be calculated accurately from a variety of traffic loads—static, impact,
                       vibratory, and moving mixes of traffic loads, including multiaxle
                       truck/trailer loads both within and outside legal weight limits. The
                       nonlinear 3D-FEM analysis allows a level of detail that aids in selecting
                       pavement materials as well as improving the accuracy of determinations of
                       the thickness needed for new, reconstructed, and overlay pavements. This
                       method can be used to analyze pavements for strengthening that may be
                       required for expected traffic loads in the future and for computing the
                       pavements’ remaining structural and operational lives.

                       Several highway departments and academic institutions have already used
                       nonlinear 3D-FEM for various structural analysis applications. The Indiana,
                       Mississippi, and Ohio departments of transportation, for example, have
                       pioneered the use of nonlinear 3D-FEM in pavement design and analysis.
                       Officials of these agencies told us that they are very satisfied with its
                       application on various road systems.

                        Dr. John Hallquist, formerly of the Lawrence Livermore National Laboratory, Livermore, California,
                       developed the nonlinear 3D-FEM computer programs DYNA-3D in 1976 and NIKE-3D in 1978. Lawrence
                       Livermore used these nonlinear 3D-FEM programs to analyze the effects of nuclear explosive devices
                       underground and the ability of intercontinental ballistic missiles to penetrate hardened military
                       structures. Improved versions called LS-DYNA-3D and LS-NIKE-3D have become available since 1989
                       and 1995 from Dr. Hallquist, Livermore Software Technology Corporation, 2876 Waverely Way,
                       Livermore, California 94550. The nonlinear 3D-FEM computer program ABAQUS has been available
                       since 1978 from Hibbitt, Karlsson and Sorensen, Inc., 1080 Main Street, Pawtucket, Rhode Island

                       Page 4                                         GAO/RCED-98-9 Highway Pavement Design Guide

In 1995, the University of Mississippi used nonlinear 3D-FEM to analyze
jointed concrete pavement for dynamic truck loads and thermal analysis.8
An official from the Mississippi State Department of Transportation told us
that this method enabled the state to determine the conditions causing the
rapid deterioration of its concrete pavement. Similarly, a senior scientist
from a firm specializing in evaluating the integrity of engineering
structures told us that, among other things, the finite element
method—combined with statistical theory (which factors in uncertainties
in material properties)—has been used to predict the expected life of a
concrete runway at Seymour Johnson Air Force Base in North Carolina.

Because it considers AASHTO’s pavement design guide to be outdated, the
School of Civil Engineering, Purdue University, also has been using
nonlinear 3D-FEM to analyze various pavement problems. The university has
used this method to analyze responses to moving multiaxle truck/trailer
loads within and outside legal weight limits on both flexible and rigid
pavements. Studies the university has conducted to verify the analyses
have shown a strong correlation between field and predicted pavement
responses (strains and deflections).9

More recently, Purdue University conducted a study—including the use of
field instrumentation, laboratory testing, field data collection, and
subgrade and core sampling—of three asphalt pavement sections with
different subdrainage configurations on a portion of Interstate 469 in Ft.
Wayne, Indiana.10 Nonlinear 3D-FEM was used to evaluate the subdrainage
performance and the analysis of moisture flow through the pavement. The
results of the study indicated a strong correlation between the predicted
and field-measured outflows of water.

The effects of high moisture conditions on pavement performance include
rutting, cracking, and faulting—leading to increased roughness, unsafe
conditions, and a loss of serviceability. A pavement design manager with
the Indiana Department of Transportation told us that the Purdue study,

  Three Dimensional-Finite Element Analysis of Jointed Concrete Pavement, Waheed Uddin, Robert M.
Hackett, Ajith Joseph, Zhou Pan, Department of Civil Engineering, University of Mississippi, and A.B.
Crawley, Mississippi Department of Transportation, TRB, Transportation Research Record No. 1482
(Washington, D.C.: 1995).
 Sameh Zagloul and Thomas D. White, Effect of Overload Vehicles on the Indiana Highway Network,
School of Civil Engineering, Purdue University, Joint Highway Research Project
(FHWA/IN/JHRP-93-5) (IN47907, June 2, 1994).
 Hossam F. Hassan and Thomas D. White, Locating the Drainage Layer for Flexible Pavements, School
of Civil Engineering, Purdue University, Joint Highway Research Project (FHWA/IN/JHRP-96/14) (IN
47907, Dec. 1996).

Page 5                                         GAO/RCED-98-9 Highway Pavement Design Guide

using nonlinear 3D-FEM, confirmed that the Department’s previously used
subdrainage design procedures resulted in a drainage outflow pipe that
was too small—thus limiting moisture outflow. Subdrainage layers with
filter layers, a perforated pipe (subdrainage collector pipe), trench
material, and an outlet pipe play a key role in reducing the extent and
duration of high moisture conditions in pavement structures and their
subgrade. The manager said that nonlinear 3D-FEM provided the (1) proper
(increased) size of drainage outlet pipe and (2) best, most efficient filter
material, which turned out to be less costly than the material previously
being used. We were told that Indiana’s Transportation Department is now
in the process of adopting nonlinear 3D-FEM as its preferred method for
designing subdrainage systems. An Indiana research section engineer also
told us that he believes that nonlinear 3D-FEM could be used by all state
highway departments to design subdrainage systems.

Battelle Memorial Institute recently applied nonlinear 3D-FEM to predict
pavement response to a broad range of vehicle loads on 4 miles of newly
constructed highway pavement (2 miles southbound and 2 miles
northbound) north of Columbus, Ohio. According to a Battelle project
scientist and an academician from Ohio University, the results of the
heavily instrumented highway test sections showed a strong correlation
with the analytical results achieved from nonlinear 3D-FEM.11 They also told
us that nonlinear 3D-FEM is the best computational method to address
pavement problems. A chief engineer of the Ohio Transportation
Department further told us that the state was pleased with Battelle’s
efforts to predict pavement response using the nonlinear method.

According to an engineer-advisor with the DOT Inspector General’s Office,
AASHTO’s pavement design guide has changed very little over the years. He
was of the opinion that new design procedures are needed, incorporating
nonlinear 3D-FEM, if FHWA and the states are going to be better able to
ensure that highway pavement is constructed, reconstructed, or overlaid
according to current FHWA policy that it be safe, durable, and

We reviewed the scope of work of the contract NCHRP awarded in
December 1996 to Nichols Consulting Engineers for the development of
the new guide. The scope of the most recent contract work does not
directly cite nonlinear 3D-FEM as a technique that can be used in the design

  James C. Kennedy, Jr., Pavement Response to Vehicular Roads—A Mechanistic Approach Involving
Nondestructive Evaluation Techniques, Battelle Memorial Institute, Columbus, Ohio, Proceedings:
International Society for Optical Engineers, Nondestructive Evaluation Techniques for Aging
Infrastructure and Manufacturing, Scottsdale, Arizona (Dec. 2-5, 1996).

Page 6                                       GAO/RCED-98-9 Highway Pavement Design Guide

                     and analysis of highway pavement. In discussions with Nichols’ project
                     manager and with an NCHRP official and in our review of the contractor’s
                     work plan for the guide, we did not find any specific reference that
                     nonlinear 3D-FEM would be investigated for inclusion or exclusion in the
                     2002 update. Through interviews with FHWA, AASHTO, and NCHRP officials,
                     we attempted to determine why the method was not specifically being
                     considered. We did not receive any explanation. However, the program
                     officer said that while the contractual documentation for this particular
                     effort does not contain specific reference to nonlinear 3D-FEM as a
                     pavement design and analysis method, the documentation does not
                     exclude the use of such a method either.

                     The pavement design guide developed and updated by AASHTO over the
Conclusions          years for designing and analyzing highway pavement structures is
                     outdated. NCHRP has undertaken a 5-year effort to update the guide
                     employing improved design approaches. Research on nonlinear 3D-FEM and
                     documented successes in its application suggest that this method could be
                     an important tool for accurately (1) designing and analyzing new highway
                     pavement structures and (2) analyzing the response of deteriorated
                     pavement structures for rehabilitation. We believe it should be considered
                     in NCHRP’s ongoing efforts to update AASHTO’s current pavement design and
                     analysis guide. The recent decision to rebid the contract for the design
                     guide update provides an opportunity for FHWA to specify the
                     consideration of this method.

                     To better assist states in designing safer, longer lasting, and more
Recommendation       cost-effective new, reconstructed, and overlay highway pavement
                     structures, we recommend that the Secretary of Transportation direct the
                     Administrator, FHWA, to ensure that nonlinear 3D-FEM is considered in the
                     current update of the pavement design guide.

                     We provided a draft of this report to DOT for its review and comment. In
Agency Comments      written comments dated October 31, 1997 (see app. II), DOT stated that it
and Our Evaluation   has maintained a long- standing commitment to ensuring that the nation’s
                     investment in its highway infrastructure is cost-effective. DOT concurred
                     with our recommendation that nonlinear 3D-FEM be considered in the
                     current update of AASHTO’s pavement design guide. DOT stated that it would
                     work with NCHRP to encourage full consideration of the method along with
                     other quantitative analytical methods.

                     Page 7                             GAO/RCED-98-9 Highway Pavement Design Guide

As part of its commitment to a cost-effective highway infrastructure, DOT
stated that FHWA has supported research efforts at its own Turner-Fairbank
Highway Research Center as well as efforts by AASHTO, NCHRP, and TRB. DOT
further stated that FHWA is fully aware of and recognizes the potential
benefits to highway design offered by 3D-FEM. According to DOT, FHWA has
supported the development of this technology at its Turner-Fairbank
facility and with individual states through the State Planning and Research
program. DOT stated that FHWA considers 3D-FEM to be a very useful
research tool for analyzing pavement structures but that it will be up to
NCHRP and AASHTO to determine whether the method has achieved the
maturity necessary to become a practical engineering tool.

We are pleased to hear of DOT’s interest in and acceptance of nonlinear
3D-FEM as an analytical tool for designing and analyzing highway pavement
structures. Such interest and acceptance was never made known to us
(1) during discussions we had with the Chief, Pavement Division, FHWA; the
project manager, AASHTO; a senior program officer, NCHRP; and the initial
contractor’s project manager for the development of the 2002 pavement
guide nor (2) in documentation we gathered and reviewed during the

We made other clarifying changes to the report as appropriate on the basis
of other comments by DOT.

We performed our work from May 1996 through October 1997 in
accordance with generally accepted government auditing standards.
Appendix I contains details on our objectives, scope, and methodology.

As you know, 31 U.S.C. 720 requires the head of a federal agency to submit
a written statement of the actions taken on our recommendations to the
Senate Committee on Governmental Affairs and to the House Committee
on Government Reform and Oversight not later than 60 days from the date
of this letter and to the House and Senate Committees on Appropriations
with the agency’s first request for appropriations made more than 60 days
after the date of this letter.

We are sending copies of this report to the Administrator, FHWA; the
Director, Office of Management and Budget; and appropriate
congressional committees. We will make copies available to others upon

Page 8                             GAO/RCED-98-9 Highway Pavement Design Guide

Please call me at (202) 512-2834 if you have any questions. Major
contributors to this report are listed in appendix III.

Sincerely yours,

John H. Anderson, Jr.
Director, Transportation Issues

Page 9                             GAO/RCED-98-9 Highway Pavement Design Guide

Letter                                                                                           1

Appendix I                                                                                      12
Objectives, Scope,
and Methodology
Appendix II                                                                                     14
Comments From the
Department of
Appendix III                                                                                    17
Major Contributors to
This Report


                        AASHTO    American Association of State Highway Transportation
                        DOT       U. S. Department of Transportation
                        FHWA      Federal Highway Administration
                        NCHRP     National Cooperative Highway Research Program
                        TRB       Transportation Reasearch Board
                        3D-FEM    3 Dimensional-Finite Element Method

                        Page 10                         GAO/RCED-98-9 Highway Pavement Design Guide
Page 11   GAO/RCED-98-9 Highway Pavement Design Guide
Appendix I

Objectives, Scope, and Methodology

              The objectives of this review were to (1) describe the roles of the Federal
              Highway Administration (FHWA) and others in developing and updating the
              pavement design guide and (2) examine the use and potential of a
              computer analysis method known as the nonlinear 3 Dimensional-Finite
              Element Method (3D-FEM) for improving the design and analysis of highway

              To accomplish these objectives, we first reviewed the American
              Association of State Highway and Transportation Officials’ (AASHTO)
              highway pavement guide, which is being used by many state departments
              of transportation as an aid in designing and analyzing pavement structures,
              federally funded and otherwise. We reviewed available literature and
              contacted officials from FHWA, AASHTO, and the Transportation Research
              Board. We also contacted contractor officials responsible for the
              development and updates of the pavement design guide. We contacted
              officials from the Transport Research Laboratory, Crawthorne, Berkshire,
              United Kingdom, and reviewed its pavement design practices. We
              contacted officials from the U.S. Army Engineer Waterways Experiment
              Station, Vicksburg, Mississippi; Indiana, Mississippi, and Ohio state
              highway departments; and various engineering consulting firms. We
              contacted academicians from the University of Arizona, the University of
              Cincinnati, Florida A&M University-Florida State University, Ohio
              University, the University of Iowa, the University of Mississippi, the
              University of Nebraska, and Purdue University, as well as Birmingham
              University in the United Kingdom. Also, we contacted scientists from
              Battelle Memorial Institute and Lawrence Livermore National Laboratory.

              We selected these educational institutions and nonprofit organizations
              because all have conducted research and development work related to
              pavement design and analysis and/or the application of nonlinear 3D-FEM
              for solving structural engineering problems. Furthermore, we performed a
              literature and database search to identify any individuals who have
              authored publications on the applications of nonlinear 3D-FEM to highway
              pavement design and analysis or other structural engineering problems.

              We discussed with FHWA and others their roles in keeping up with and
              promoting up-to-date techniques regarding pavement design and analysis.
              We reviewed FHWA’s pavement policy issued in December 1996, which
              states that pavements should be designed to accommodate current and
              predicted traffic needs in a safe, durable, and cost-effective manner.

              Page 12                            GAO/RCED-98-9 Highway Pavement Design Guide
Appendix I
Objectives, Scope, and Methodology

More broadly, we used in this review information we obtained through
attendance at the Fourth International Conference on the Bearing
Capacity of Roads and Airfields held in July 1994 in Minneapolis,
Minnesota; the Third Materials Engineering Conference held in November
1994 in San Diego, California; annual Transportation Research Board
meetings held in January 1995 and in January 1997 in Washington, D.C.;
and the Structures Congress XV held in April 1997 in Portland, Oregon.

Page 13                              GAO/RCED-98-9 Highway Pavement Design Guide
Appendix II

Comments From the Department of

              Page 14     GAO/RCED-98-9 Highway Pavement Design Guide
Appendix II
Comments From the Department of

Page 15                           GAO/RCED-98-9 Highway Pavement Design Guide
Appendix II
Comments From the Department of

Page 16                           GAO/RCED-98-9 Highway Pavement Design Guide
Appendix III

Major Contributors to This Report

                       Dr. Manohar Singh, P.E., Engineering Consultant
Resources,             Ralph W. Lamoreaux, Assistant Director
Community, and
Development Division

(342929)               Page 17                          GAO/RCED-98-9 Highway Pavement Design Guide
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