Airfield Pavement: Keeping Nation's Runways in Good Condition Could
Require Substantially Higher Spending (Chapter Report, 07/31/98,
GAO/RCED-98-226).

Pursuant to a congressional request, GAO provided information on runway
conditions at national system airports and cost estimates for
maintaining and rehabilitating these runways over the next 10 years,
focusing on the: (1) current condition of the nation's airport runways;
(2) likely cost of rehabilitation and preventive maintenance for these
runways over the next 10 years; (3) Federal Aviation Administration's
(FAA) basis for setting priorities among requests for Airport
Improvement Program (AIP) grants for runway rehabilitation and
maintenance; and (4) results of the demonstration project authorized by
Congress in 1996 to address concerns that a lack of funding was
hampering runway maintenance at small airports.

GAO noted that: (1) most runway pavement is currently in generally good
condition; (2) about three-fourths of the runways included in GAO's
database on pavement condition were rated good to excellent, while
one-fourth were rated fair to poor; (3) a statistical model predicted
that most of the runways not in GAO's database were also in good to
excellent condition; (4) however, in the next 10 years, many airports in
GAO's database will face substantial work keeping runways in generally
good condition; (5) FAA and pavement experts believe that the most
economical way to lengthen pavement life at many airports is to
rehabilitate runways when they are still in good condition; (6) waiting
often increases costs because more expensive methods must be used; (7)
the cost of keeping runways in generally good condition over the next 10
years will be beyond the average $162 million historically spent in the
AIP for this purpose each year; (8) for the 35 percent of national
system airports in its database, GAO estimated future costs in two ways;
(9) assuming that airports could fund projects before runway pavement
deterioration accelerated to the point at which more expensive
approaches would have to be used, an estimated $1.38 billion would be
needed at these airports over the next 10 years; (10) these airports
could then choose a less expensive rehabilitation option, rather than a
more costly reconstruction method; (11) assuming that these airports
would have about $162 million per year in federal funds to spend, they
would face an unmet need of $2.37 billion after 10 years, a higher
amount than under the first estimate; (12) FAA's system for setting
priorities among grant applications gives runway rehabilitation projects
higher priority than most other projects; (13) however, FAA does not
have an accurate, consistent source of information about detailed runway
conditions at all airports in the national system to consider during
this process; (14) for fiscal year (FY) 1997 and FY 1998, the states and
local airport authorities have shown limited interest in participating
in the pilot program authorized by Congress for pavement maintenance
grants at nonprimary airports; (15) in FY 1997, FAA received expressions
of interest from 14 airport owners and states that provide assistance to
airports within their borders and awarded grants to 1 airport owner and
3 states; (16) six candidates expressed interest in participating in the
second year of the program; and (17) a GAO survey of state aviation
departments revealed no dominant reason for the limited amount of
interest.

--------------------------- Indexing Terms -----------------------------

 REPORTNUM:  RCED-98-226
     TITLE:  Airfield Pavement: Keeping Nation's Runways in Good 
             Condition Could Require Substantially Higher Spending
      DATE:  07/31/98
   SUBJECT:  Airports
             Future budget projections
             Federal aid for transportation
             Federal grants
             Cost effectiveness analysis
             Repair costs
             Maintenance costs
             Maintenance (upkeep)
             Grant administration
IDENTIFIER:  FAA Airport Improvement Program
             FAA National Priority System
             FAA Capital Improvement Plan
             FAA Airport Safety Data Program
             
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Cover
================================================================ COVER


Report to the Chairman, Committee on Commerce, Science, and
Transportation, U.S.  Senate

July 1998

AIRFIELD PAVEMENT - KEEPING
NATION'S RUNWAYS IN GOOD CONDITION
COULD REQUIRE SUBSTANTIALLY HIGHER
SPENDING

GAO/RCED-98-226

Airfield Pavement

(341529)


Abbreviations
=============================================================== ABBREV

  AIP - Airport Improvement Program
  CIP - Capital Improvement Plan
  FAA - Federal Aviation Administration
  PCI - pavement condition index
  PMS - pavement management system
  NPIAS - National Plan of Integrated Airport Systems

Letter
=============================================================== LETTER

RCED

B-276930

July 31, 1998

The Honorable John McCain
Chairman, Committee on Commerce,
 Science, and Transportation
United States Senate

Dear Mr.  Chairman: 

In response to your request, this report discusses runway conditions
at national system airports and provides cost estimates for
maintaining and rehabilitating these runways over the next 10 years. 
This report contains recommendations to the Secretary of
Transportation to assist the Federal Aviation Administration in
better targeting funds for the Airport Improvement Program. 

We will send copies of this report to appropriate congressional
committees, the Secretary of Transportation, the Administrator of the
Federal Aviation Administration, and other interested parties.  We
also will make copies available to others upon request. 

If you or your staff have any questions about this report, please
call me at (202) 512-3650.  Major contributors to this report are
listed in appendix VI. 

Sincerely yours,

Gerald L.  Dillingham
Associate Director,
 Transportation Issues


EXECUTIVE SUMMARY
============================================================ Chapter 0


   PURPOSE
---------------------------------------------------------- Chapter 0:1

Since 1982, the Airport Improvement Program (AIP) has provided about
$2.2 billion in federal grants for rehabilitating and maintaining
airport runways.  Administered by the Federal Aviation Administration
(FAA), this program is a major source of runway rehabilitation
funding for the 3,300-plus airports that constitute FAA's national
airport system--the primary network of airports throughout the
country.  At the request of the Chairman of the Senate Committee on
Commerce, Science, and Transportation, GAO addressed the following
issues concerning this program:  (1) the current condition of the
nation's airport runways, (2) the likely cost of rehabilitation and
preventive maintenance for these runways over the next 10 years, (3)
FAA's basis for setting priorities among requests for AIP grants for
runway rehabilitation and maintenance, and (4) the results of the
demonstration project authorized by the Congress in 1996 to address
concerns that a lack of funding was hampering runway maintenance at
small airports. 

GAO developed a comprehensive picture of runway conditions by
assembling a detailed database covering about 35 percent of the
airports in the national system and determined, using statistical
methods, that conditions at the remaining 65 percent of the airports
were comparable.  The airports in the database represent a cross
section of all sizes of airports.  Although this approach allows
systemwide estimates about current runway conditions, the lack of
detailed information on pavement conditions at 65 percent of the
airports prohibited any generalization about their future conditions
or the cost to rehabilitate or maintain their runways. 


   BACKGROUND
---------------------------------------------------------- Chapter 0:2

Runways, like highways, are prone to deterioration from weather and
usage.  Left unchecked, such deterioration can eventually pose safety
risks to planes that are taking off or landing.  FAA considers
airport runway conditions to be so important that rehabilitating
aging pavement is among its highest priorities for awarding an AIP
grant.  Rehabilitation projects typically involve adding a
strengthening layer to an existing surface that has not deteriorated
to the point of needing complete replacement.  Preventive maintenance
projects, which are lower on FAA's priority list, are designed to
forestall the need for runway rehabilitation.  Generally, however,
AIP grants are not available for routine maintenance unless such
maintenance is associated with an eligible repair project.  In 1996,
the Congress authorized FAA to implement a pavement maintenance pilot
project to preserve and extend the life of airfield pavements at
small airports by allowing AIP grants to be used for stand-alone
routine maintenance projects.  To obtain additional information to
support a decision to maintain or rehabilitate a runway, many
airports conduct surveys on pavement condition that produce a
pavement condition index (PCI).  The PCI survey consists primarily of
a rigorous visual inspection of the pavement surfaces for signs of
deterioration.  The PCI rates pavements on a scale of 100 (excellent)
to 0 (failed) but clusters the numeric rankings into seven
categories:  "excellent," "very good," "good," "fair," "poor," "very
poor," and "failed." FAA also has runway pavement information
obtained as part of its inspections under the Airport Safety Data
Program (designed to collect and disseminate information about
airports to pilots and other users).  The information collected
during these inspections is the result of a quick look at the runways
and a subsequent rating of "good," "fair," or "poor" and was not
designed to support airports' decisions about pavement management. 

FAA's national airport system includes about 547 airports that handle
a significant amount of commercial passenger activity; the rest,
called "general aviation" airports, serve primarily privately owned
aircraft.  General aviation airports particularly depend on AIP
funding, while busy commercial service airports generally have more
access to other funding sources, such as bonds or passenger facility
charges added to the cost of airline tickets. 


   RESULTS IN BRIEF
---------------------------------------------------------- Chapter 0:3

Most runway pavement is currently in generally good condition.  About
three-fourths of the runways included in GAO's database on pavement
condition (which provides a numerical score based on a visual
inspection that indicates the pavement's condition) were rated good
to excellent, while one-fourth were rated fair to poor.  A
statistical model predicted that most of the runways not in GAO's
database were also in good to excellent condition.  However, in the
next 10 years, many airports in GAO's database will face substantial
work keeping runways in generally good condition, particularly in
doing so at the least cost.  FAA and pavement experts believe that
the most economical way to lengthen pavement life at many airports is
to rehabilitate runways when they are still in good condition. 
Waiting often increases costs because more expensive methods must be
used.  In all, about 26 percent of the runways in GAO's PCI database
had already reached or passed the point at which they could be
rehabilitated most economically, and a statistical model predicted
that about 17 percent of the runways not in GAO's PCI database are at
the same point. 

The cost of keeping runways in generally good condition over the next
10 years will be beyond the average $162 million historically spent
in the Airport Improvement Program for this purpose each year.  For
the 35 percent of national system airports in its database, GAO
estimated future costs in two ways.  First, assuming that airports
could fund projects before runway pavement deterioration accelerated
to the point at which more expensive approaches would have to be
used, an estimated $1.38 billion would be needed at these airports
over the next 10 years.  These airports could then choose a less
expensive rehabilitation option, such as an overlay, rather than a
more costly reconstruction method.  However, as much as $774 million
of this amount could be used in the first year because a number of
runways have already deteriorated to the point at which more
expensive approaches would have to be used.  This amount is 5 times
the current level of spending for runway rehabilitation systemwide. 
Second, assuming that these airports would have about $162 million
per year in federal funds to spend (the amount historically spent
systemwide), they would face an unmet need of $2.37 billion after 10
years, even though they had spent $1.62 billion, a higher amount than
under the first estimate.  Total costs are much higher under the
second estimate because many projects would have to be deferred
beyond the first year, and pavement would continue to rapidly
deteriorate and become more expensive to rehabilitate. 

FAA's system for setting priorities among grant applications gives
runway rehabilitation projects higher priority than most other
projects, enhancing the likelihood that the projects submitted for
approval by FAA's regional offices will receive funding.  However,
FAA does not have an accurate, consistent source of information about
detailed runway conditions at all airports in the national system to
consider during this process.  Data gathered during PCI inspections
provide more detailed information that could be used to make grant
decisions; however, less than half of the airports in the national
system choose to obtain the more rigorous inspection. 

For fiscal years 1997 and 1998, the states and local airport
authorities have shown limited interest in participating in the pilot
program authorized by the Congress for pavement maintenance grants at
nonprimary airports.  The reasons for not participating ranged from
difficulties with the application process to a desire to spend the
limited dollars in the Airport Improvement Program on projects
considered to be of higher priority.  In fiscal year 1997, FAA
received expressions of interest from 14 airport owners and states
that provide assistance to airports within their borders and awarded
grants to 1 airport owner and 3 states.  Six candidates--three of the
original four awardees plus three more states--expressed interest in
participating in the second year of the program, and FAA so far has
awarded three grants (to three original participants).  A GAO survey
of state aviation departments revealed no dominant reason for the
limited amount of interest. 


   PRINCIPAL FINDINGS
---------------------------------------------------------- Chapter 0:4


      MOST AIRPORT RUNWAYS ARE IN
      GENERALLY GOOD CONDITION
-------------------------------------------------------- Chapter 0:4.1

The airports in the national system have runways that are in
generally good condition.  Seventy-seven percent of the runways in
GAO's runway pavement database were ranked in the three highest
categories--excellent, very good, and good.  Eleven percent were
rated fair; the remainder were rated in the three lowest
categories--poor, very poor, or failed.  Using various statistical
techniques,\1 GAO concluded that most airports not in the database
had runways that were likely to be in similar condition. 

However, a small but significant portion of runway pavement may need
immediate attention:  12 percent of the runways in the database were
rated poor or below.  Even more important in assessing future work,
however, is the fact that airports need to consider rehabilitating
runway pavement long before it has deteriorated to poor condition. 
Rehabilitating pavement in poor condition may cost 2 to 3 times as
much as rehabilitating pavement in good condition because more
expensive methods may be used.  About 33 percent of the airports in
the database and about 26 percent of the airports not in the database
had at least one-third of their runways at (or past) the point at
which more expensive rehabilitation methods would have to be used. 


--------------------
\1 GAO collected detailed PCI data from about 35 percent of the
airports eligible for federal funding and used the data to create a
runway pavement database.  The remaining 65 percent of the airports
eligible for federal funding did not have PCI information available. 
To predict the likely runway pavement conditions at these airports,
GAO developed a model based on other airport characteristics (such as
age, the type of pavement, climate, and the number of takeoffs and
landings). 


      AIRPORTS WILL LIKELY NEED TO
      INCREASE SPENDING ON RUNWAYS
-------------------------------------------------------- Chapter 0:4.2

Any estimate of future rehabilitation costs must be based on a set of
assumptions--such as how much money will be available and when
airports will decide to undertake particular projects--that can only
partially reflect the timing and type of rehabilitation to be
undertaken.  GAO developed two estimates of rehabilitation and
preventive maintenance costs for those airports contained in the
database.  The first scenario showed an estimated cost of $1.38
billion over 10 years.  This estimate assumed that airports would be
able to conduct work before runway pavement deteriorated to the point
that more expensive approaches would have to be used.  Because 26
percent of the runways in our database were already at that point,
the first-year expenditure of $774 million would far outstrip the
historical annual level of federal AIP money available for such work
at all eligible airports ($162 million). 

A second estimate assumed that these airports would have about $162
million a year--the estimated historical spending of AIP funds for
runway maintenance and reconstruction for all airports in the
national system--to spend on rehabilitation.  This assumption may
still be optimistic, given that $162 million is for rehabilitation
for all airports in the national system, not just the 35 percent in
GAO's database.  Even though more money would be spent under this
second scenario in 10 years ($1.62 billion), not all airports would
receive funding at the point that it would be most economical to
rehabilitate their runways.  Under this scenario, the cost of
unfunded runway projects would be about $2.37 billion because
deferred rehabilitation costs so much more.  This higher cost
illustrates the importance of knowing the point of deterioration at
which more expensive approaches would have to be used. 


      FAA'S METHOD FOR FUNDING
      RUNWAY PROJECTS COULD
      BENEFIT FROM BETTER
      INFORMATION
-------------------------------------------------------- Chapter 0:4.3

The National Priority System, FAA's primary method for determining
which AIP grant applications from individual airports should be
funded, establishes a priority rating on the basis of factors such as
the purpose and type of the project.  Runway rehabilitation projects
fare well in this system and are typically funded ahead of most other
types of projects.  Most applications for such projects received
funding in fiscal year 1997, according to FAA officials.  However,
local FAA officials said that they forward only those applications
they are relatively certain will be funded. 

FAA's priority system is not well equipped to determine which
proposed rehabilitation projects will deliver the best return for the
dollars spent.  Waiting to rehabilitate a runway until the pavement
has seriously deteriorated can mean that rehabilitation will cost 2
to 3 times as much as it would have if rehabilitation had occurred
earlier.  The key to identifying the best time to conduct
rehabilitation is having comprehensive knowledge of pavement
conditions.  Currently, fewer than half of the airports in the
national system have information systems that will provide this
knowledge.  Furthermore, when allocating AIP funds, FAA does not
evaluate the cost-effectiveness of the rehabilitation projects it
approves. 

FAA could obtain the needed information either by improving its
existing information on runway condition or by obtaining PCI
information from all airports.  FAA's existing runway information,
obtained during its inspections under the Airport Safety Data
Program, provides only the most general of pavement assessments for
all runways.  This information is designed to inform airport users of
the overall conditions of the airports, not to serve as a pavement
management tool.  These assessments are made by safety inspectors who
receive little training in how to examine pavement conditions. 
Moreover, FAA officials acknowledge that the criteria used for the
inspections are vague and open to interpretation.  Improving its
existing information would require FAA to take such actions as
developing sufficient rating criteria and providing more in-depth
training for inspectors.  On the other hand, the PCI rating was
designed to be used as a pavement management tool to help
decisionmakers determine when pavements need maintenance or
rehabilitation.  However, less than half of the airports in the
national system have PCI ratings.  If FAA were to rely on PCI ratings
to make funding decisions, it would need to require all airports to
submit PCI-based justifications as part of the airport master
planning or project application process, and it would need to take
steps to ensure that airports had comparable data. 


      NONPRIMARY AIRPORTS'
      PARTICIPATION IN PILOT
      PROJECT FOR PAVEMENT
      MAINTENANCE GRANTS IS
      LIMITED
-------------------------------------------------------- Chapter 0:4.4

FAA implemented the demonstration project as a program for adding
stand-alone crack sealing, a relatively inexpensive maintenance item,
to the list of projects eligible for AIP funds at nonprimary
airports.\2 In fiscal year 1997, 10 states that provide assistance to
airports within their borders expressed an interest in this funding,
as did four airport owners.  FAA awarded grants totaling about
$566,000 to three states and one airport owner.  It determined that
about half of the applicants did not meet the guidelines established
for participation, such as a preference for proposals that would
apply to multiple airports and a preference for locating at least two
of the pilot projects in states with no large commercial airports. 
The approved projects are all for stand-alone crack-sealing projects
and other types of related maintenance.  In 1998, three of the four
original awardees again received pilot program grants, and FAA hopes
to award the remaining pilot program grants before the end of fiscal
year 1998. 

GAO contacted every state to determine why so few had expressed
interest in the pilot program.  Their responses varied greatly, from
not having enough time or staff to apply to having their own programs
to pay for such work.  The relatively limited number of applications
suggests that few states and airports may be interested in using AIP
funds for this purpose.  At the same time, however, the successful
applicants said they would not have been able to finance this
maintenance in other ways. 


--------------------
\2 Maintenance projects, including stand-alone crack sealing, are
traditionally not eligible for AIP grants. 


   RECOMMENDATIONS
---------------------------------------------------------- Chapter 0:5

To enable FAA to make the most cost-effective decisions when awarding
Airport Improvement Program grants for runway rehabilitation
projects, GAO recommends that the Secretary of Transportation direct
the Administrator of FAA to evaluate options for improving the
quality of information on airfield pavement conditions for national
system airports.  These options include, but are not limited to,

  -- improving FAA's existing information on pavement conditions by
     reviewing and revising rating criteria and providing adequate
     training for inspectors;

  -- requiring airports to submit index ratings on pavement condition
     as part of the support for their master plans and applications
     for relevant discretionary grants under the Airport Improvement
     Program; and

  -- requiring all airports in the national airport system to submit
     index ratings on pavement condition on a regular basis and using
     this information to create a database on pavement conditions for
     evaluating the cost-effectiveness of project applications and
     forecasting anticipated pavement needs. 

Because of the limited interest expressed to date in the pilot
program for pavement maintenance, the Secretary of Transportation
should direct the Administrator of FAA to review the need for a
separate pilot for airfield pavement maintenance.  To accommodate
applicants interested in using Airport Improvement Program funds for
stand-alone crack-sealing projects, the Administrator should
determine if it would be necessary to seek legislation before adding
stand-alone crack- sealing projects to the regular list of eligible
projects for the Airport Improvement Program. 


   AGENCY COMMENTS
---------------------------------------------------------- Chapter 0:6

GAO provided copies of a draft of this report to the Federal Aviation
Administration (FAA) for review and comment.  GAO discussed the
report with FAA officials, including the Director, Office of Airport
Safety and Standards, and the Manager, Airport Financial Assistance
Division.  FAA generally agreed with the report's findings,
conclusions, and recommendations.  With regard to the
recommendations, FAA said it would consider options for developing a
pavement management system and would explore the possibility of
making crack-sealing eligible for Airport Improvement Program
funding.  FAA also provided some technical comments, which GAO
incorporated into the report as appropriate. 


INTRODUCTION
============================================================ Chapter 1

The federal government assists with funding for rehabilitating and
maintaining runways at U.S.  airports.  It does so through the
Airport Improvement Program (AIP), which provides grants for many
types of projects at more than 3,300 airports nationwide.  The
Federal Aviation Administration (FAA) administers AIP and is
responsible for distributing program funds. 


   FEDERAL FUNDING EFFORTS FOCUS
   ON 3,300 AIRPORTS IN THE
   NATIONAL SYSTEM
---------------------------------------------------------- Chapter 1:1

The United States possesses the largest, most extensive aviation
system in the world, with more than 18,000 airports.  These airports
range from large commercial airports, such as Chicago's O'Hare
International Airport, to small, privately owned grass landing strips
that may serve only a few aircraft a year.  About 3,300 of these
airports are designated as part of a national system providing a
network of air transportation to every part of the country.\1
National system airports are of two types:  547 that handle regularly
scheduled commercial airline traffic (called commercial service
airports) and 2,767 that are used primarily by privately owned
aircraft (called general aviation airports).  All of these airports,
whether commercial service or general aviation, are eligible for
federal funding through AIP grants.  A federal statute and FAA's
rules establish which types of airport development projects are
eligible for AIP funding.\2


--------------------
\1 This national system is described in the National Plan of
Integrated Airport Systems (NPIAS). 

\2 These development projects are listed in the AIP Handbook (FAA
Order 5100.38A). 


   RUNWAY PAVEMENT:  TERMS AND
   CONCEPTS
---------------------------------------------------------- Chapter 1:2

As soon as they are built, runways, like other airfield pavements,\3
begin a gradual deterioration attributable to the effects of
weathering and the action of aircraft traffic.  Left untended, such
deterioration may affect the safe operation of aircraft take-offs and
landings.  Proper runway construction and maintenance enhances the
longevity of the pavement. 

Runways can be constructed of flexible (asphalt) or rigid (concrete)
materials.  Concrete, a rigid pavement that can remain useful for 20
to 40 years, is typically found at large commercial service airports
and at airports that formerly were military bases, according to the
manager of FAA's Engineering and Specifications Division.  Concrete
runways can be laid out in square or rectangular slabs that may be
divided by joints to allow for expansion and contraction as the
weather changes.  This official also noted that asphalt, a flexible
pavement that can deteriorate very quickly in cold climates and more
slowly in mild ones, is the runway pavement at most small airports. 
With proper design, construction, and maintenance, an asphalt runway
can last 15 to 20 years or more before needing rehabilitation. 


--------------------
\3 Other airfield pavements include taxiways, which provide access
between runways and terminals; hangars, or other areas where aircraft
are parked; and aprons, which are the paved areas around terminals or
hangars. 


      TYPES OF PAVEMENT-RELATED
      PROBLEMS AND CORRECTIVE
      ACTIONS
-------------------------------------------------------- Chapter 1:2.1

Both concrete and asphalt runways are subject to wear from two main
factors--usage and weather.  This wear causes "distresses"--cracks
and other types of damage.  Both concrete and asphalt runways are
also subject to disintegration, distortion, and wear that gives
aircraft less traction.  In concrete pavements, these distresses
include, for example, the hairline cracking of the slabs and the
buildup of rubber deposits from tires.  Asphalt pavement distresses
include the wearing away of the pavement surface (raveling) and ruts
in the wheel paths. 

A number of actions can be taken to repair the distresses that occur
in concrete and asphalt pavements.  The determining factor in
selecting an action is the degree to which the pavement has
deteriorated.  Less deteriorated pavements generally require
maintenance, while more extensively deteriorated pavements require
rehabilitation.  FAA defines maintenance as "any regular or recurring
work necessary, on a continuing basis, to preserve existing airport
facilities in good condition, any work involved in the care or
cleaning of existing airport facilities, and incidental or minor
repair work on existing airport facilities." A typical maintenance
repair is crack-sealing.  FAA defines rehabilitation as the
"development required to preserve, repair, or restore the functional
integrity" of the pavement.  One example of a rehabilitation project
is a structural overlay (laying more asphalt on the runway surface). 
In FAA's AIP Handbook, work items eligible for funds under airfield
paving focus on construction and rehabilitation, including the
reconstruction and repair of runways, taxiways, and aprons. 
Stand-alone crack-sealing and other minor maintenance items are
generally not eligible.\4


--------------------
\4 In some circumstances, routine maintenance items are eligible for
funding if associated with an eligible repair project.  In addition,
FAA's pilot maintenance program allows selected airports to use AIP
funds for stand-alone crack-sealing projects. 


      KEY PAVEMENT MANAGEMENT
      PRINCIPLES AND APPROACHES
-------------------------------------------------------- Chapter 1:2.2

Though approaches to repairing pavements may differ, some experts
note that appropriately timed maintenance and rehabilitation
forestalls the need to replace the pavement entirely--a far more
expensive step.  Figure 1.1 illustrates the decision-making
process--with budget considerations taken into account--for ensuring
that a pavement lasts as long as possible before it needs to be
replaced.  Maintenance and repairs, such as crack-sealing, can
minimize pavement deterioration.  Similarly, rehabilitation, such as
a structural overlay, can extend the time needed until the pavement
must be replaced.  On the other hand, not conducting such work at the
proper time can shorten pavement life.  As FAA notes in its guidance
on airport pavement maintenance, "a delay in repairing pavements may
allow minor distresses to progress into major failures."\5

   Figure 1.1:  Decision-making
   Process to Ensure a Long
   Pavement Life

   (See figure in printed
   edition.)

Note:  This figure was developed with the following assumptions in
mind:  (1) budget considerations are always a factor in determining
repair options; (2) pavements do not face some special circumstances
that would require repair before they reach the point of needing
rehabilitation; and (3) if a lack of funds precludes work from being
done, the option to do something in the future will be reevaluated. 

Source:  Adapted from M.Y.  Shahin, Pavement Management for Airports,
Roads, and Parking Lots (New York, NY:  Chapman & Hall, 1994). 

Because of the importance of good pavement management, the Congress
and FAA have taken steps to ensure that airports receiving federal
funds have a pavement maintenance program in place.  Since AIP's
inception, the Congress has required airport officials to assure FAA
that they will maintain their airport and all its facilities,
including pavements, and since 1995, the Congress has required the
recipients of grants to rehabilitate airport pavement to provide
assurance that a maintenance management program for their airport is
in place.\6 FAA issued advisory circulars on the maintenance of
airport pavements in 1982 and pavement management systems in 1988. 

In fiscal year 1995, FAA issued guidelines recommending the elements
that should be included in management programs to maintain pavement. 
These guidelines state that, at a minimum, any maintenance programs
should include a pavement inventory, inspections, and records
documenting the inspections' findings and the maintenance that has
been scheduled or performed. 

Some airports and state-level agencies that coordinate
airport-related activity have chosen to obtain additional pavement
information by conducting surveys on pavement condition that produces
a pavement condition index (PCI).  The PCI survey consists primarily
of a visual inspection of the pavement surfaces for signs of pavement
deterioration caused by the environment and the level of aircraft
traffic.\7 The PCI index rates pavements on a scale of 100
(excellent) to 0 (failed) but clusters the numeric rankings into
seven categories:  "excellent," "very good," "good," "fair," "poor,"
"very poor," and "failed." Airports can use PCI information as a
pavement management tool to identify pavement sections that could
require maintenance or rehabilitation.  Once problem sections are
identified, airports can conduct more extensive pavement testing to
determine the type of maintenance or rehabilitation that would be
most appropriate.  (Chapters 2 and 4 of this report discuss aspects
of this approach in more detail.)

FAA currently has some information on runway surface conditions for
each airport in the country that it has collected as part of its
inspections under the Airport Safety Data Program.  This program is
designed to meet FAA's statutory requirement to collect and
disseminate airport information to ensure the safe and efficient use
of the airport by airport users.  Inspections catalogue all aspects
of the airport, including the runway condition, but, unlike the PCI
rating, these inspections were designed to be a quick look at the
pavement surface--not a detailed inspection. 


--------------------
\5 Federal Aviation Administration, Guidelines and Procedures for
Maintenance of Airport Pavements (Advisory Circular 150/5380-6, Dec. 
3, 1982). 

\6 See 49 U.S.C.  section 47105(e). 

\7 FAA's Guidelines and Procedures for Maintenance of Airport
Pavements (AC:  150/5380-6, Dec.  3, 1982) and American Standard Test
Method Designation D 5340-93 outline methods for conducting PCI
surveys. 


   ROLE OF AIP IN FUNDING AIRFIELD
   PAVEMENT PROJECTS
---------------------------------------------------------- Chapter 1:3

AIP is the primary source of federal assistance to airports.  AIP
grants are funded through the Airport and Airway Trust Fund, which is
financed by taxes on domestic airline tickets,\8 international air
travel from the United States, domestic cargo transported by air, and
noncommercial aviation fuel.  During fiscal years 1982 through 1997,
FAA awarded more than $20 billion in AIP grants--about $1.6 billion
of it in fiscal year 1997.  AIP grants can be used for a wide variety
of projects, but not for everything.  For example, runways, lighting,
navigational aids, access roadways, and pedestrian walkways are
eligible, but hangars and the revenue-producing areas of terminals
(such as ticket counters or concessions) are not.  During fiscal
years 1982 through 1997, more than $10 billion, or about 54 percent
of the total amount of AIP grants, went for pavement-related
projects, such as rehabilitating or constructing runways or taxiways. 
(See fig.  1.2.)

   Figure 1.2:  Pavement-Related
   Grants as a Portion of All AIP
   Grants, Fiscal Years 1982-97

   (See figure in printed
   edition.)

Source:  FAA data. 

Of the $10 billion awarded for pavement-related projects, about $5
billion was for runways.  Grants for rehabilitating runways totaled
more than $2.2 billion--about the same amount as grants for building
new runways.  (See fig.  1.3.) Grants categorized as "seal coats" (a
top coat of asphalt applied to the runway surface) totaled about $25
million, or less than 1 percent of the total.\9 About $580 million
went for other projects, such as grooving runway pavements to provide
more traction. 

   Figure 1.3:  Allocation of AIP
   Runway-Related Project Grants,
   Fiscal Years 1982-97

   (See figure in printed
   edition.)

Note:  Other projects include grooving, friction treatments,
helicopter landing areas, noise compatibility (as a consequence of a
runway project), miscellaneous safety areas, and environmental
mitigation construction (as a consequence of a runway project). 

Source:  FAA data. 

AIP has two categories of grant funding--apportionment and
discretionary.  Apportionment funds are distributed by formula to
commercial service airports and the states, while discretionary funds
are awarded by FAA on a project-by-project basis.  For some airports,
runway projects involve a combination of both apportionment and
discretionary AIP funds.  Any airport in the national system is
eligible to apply for a discretionary grant.  (The process FAA uses
to consider these applications is discussed in ch.  4.) All airports
receiving AIP funds must agree to provide a financial share, ranging
from 10 to 25 percent of the total cost of the project, before FAA
will award a grant.\10

To provide additional help for nonprimary airports, a pavement
maintenance pilot program was authorized under the Federal Aviation
Reauthorization Act of 1996.\11

Beginning in fiscal year 1997, the FAA Administrator was authorized
to fund up to 10 pilot projects for pavement maintenance at
nonprimary airports "to preserve and extend the life of airport
runways, taxiways, and aprons." FAA implemented the pilot program to
make stand-alone crack-sealing temporarily eligible for AIP funding. 


--------------------
\8 These taxes are different from passenger facility charges, which
are charges that public agencies controlling commercial service
airports can, with FAA's permission, levy on enplaning passengers
using the airport. 

\9 Under FAA's Handbook, these types of pavement repair projects are
eligible when periodic pavement surveys reveal trends in
deterioration and it is determined that a repair will retain the
serviceability of the pavement. 

\10 Airports rely on a number of sources for these funds, including
airport revenue, federal and state grants, passenger facility
charges, state and local contributions, and tax-exempt bonds.  For
more information on these other sources of airport capital
development revenue, see Airport Financing:  Funding Sources for
Airport Development (GAO/RCED-98-71, Mar.  12, 1998). 

\11 See 49 U.S.C.  section 47132. 


   OBJECTIVES, SCOPE, AND
   METHODOLOGY
---------------------------------------------------------- Chapter 1:4

At the request of the Chairman of the Senate Committee on Commerce,
Science, and Transportation, we addressed the following issues
concerning the AIP:  (1) the current condition of the nation's
airport runways, (2) the likely cost of rehabilitation and preventive
maintenance for these runways over the next 10 years, (3) FAA's basis
for setting priorities among requests for AIP grants for runway
rehabilitation and maintenance, and (4) the results of the
demonstration project authorized by the Congress in 1996 to address
concerns that a lack of funding was hampering runway pavement
maintenance at small airports. 

To determine the condition of the nation's runways, we first
evaluated a variety of data sources on pavement condition, including
FAA's Airport Safety Data Program, PCI information detailing specific
information about airports' runway pavements, and similar indexes
developed by some states and airports.  While PCI inspections provide
information only about the surface condition of the runway, we
determined that it was the best source of information for our
purposes.  To collect PCI data, we contacted all primary (large,
medium, small, and nonhub) airports and the states to determine
whether they had PCI inspection data for their airports.  On the
basis of this information, we created a PCI database for 35 percent
of the airports eligible for federal grants.  (Information on the
airports included in the database is available upon request.) Using
the database in conjunction with pavement management software, we
projected runway conditions for the years 1998 and 2007.  Using this
database, we also conducted a regression analysis to determine which
airport-specific variables were likely to predict a runway's PCI
rating.  We then used this information to estimate the pavement
condition index for airports with similar characteristics but without
any current information on pavement condition.  We also visited 80
airports of various sizes to confirm that the information we had on
pavement condition was accurate and to discuss pavement maintenance
and rehabilitation with various airport and state aviation officials. 
(For information on the construction of the database or the
regression analysis used to predict condition for airports, see app. 
I; for a list of the airports visited, see app.  II.)

To determine the likely cost of maintaining and reconstructing
runways over the next 10 years, we used pavement management software
to project maintenance and reconstruction costs for each runway
section in our database for two financing scenarios.  We were unable
to predict the likely cost of maintaining or reconstructing the
runways for which we had no PCI data because the forecasting model
required specific information about the particular distress problems
in the runway in order to determine the appropriate treatment.  (For
additional information on the construction of the financing
scenarios, see app.  I.) We obtained assistance in interpreting the
condition and cost data from a panel of airport pavement advisors. 
The panel included representatives from the asphalt and concrete
industry, airport maintenance officials, state aviation officials,
and consultants.  (For a complete list of the panel members, refer to
app.  V.)

To determine the basis on which FAA ranks requests for
pavement-related AIP grants, we examined FAA's current system for
ranking projects and interviewed FAA headquarters, regional, and
district officials about their procedures for ranking projects.  In
addition, we developed options for FAA to more appropriately time the
funding of maintenance and rehabilitation projects. 

To determine the results from the pilot program for pavement
maintenance, we surveyed the 50 state aviation programs by mail in
September 1997.  The questionnaire asked the states whether they had
applied for the pilot program and, if they had not, what their
reasons were.  (See app.  III for a copy of this questionnaire).  We
also surveyed 23 of the 24 FAA offices responsible for airports by
telephone in October 1997 to determine whether any states or airport
owners in their jurisdictions had applied for maintenance grants
under the pilot program.\12 If any had applied, we tried to determine
which applications were denied and why.  We achieved a 100-percent
response rate for both surveys.  We also visited all four awardees
that had received pilot program grants in fiscal year 1997. 

Our work was done from May 1997 through July 1998 in accordance with
generally accepted government auditing standards. 


--------------------
\12 We did not include the FAA regional office covering Alaska
because the climate and conditions under which Alaskan airports
operate differ considerably from the rest of the country. 


MOST AIRPORT RUNWAYS ARE IN
GENERALLY GOOD CONDITION, BUT
AIRPORTS STILL FACE A NEED FOR
CONSIDERABLE REHABILITATION WORK
OVER NEXT 10 YEARS
============================================================ Chapter 2

Our database analysis and statistical modeling indicates that most
runway pavements are in generally good condition.  About
three-fourths of the runways included in our database are currently
rated in good to excellent condition.\1 By applying statistical
modeling, we were able to conclude that the runways without detailed
pavement data were likely to be similar to those that had specific
data on their pavement conditions.  Although the runways are in
generally good condition, considerable work will be required to keep
them that way.  FAA and pavement experts believe that the most
economical way to lengthen pavement life is to rehabilitate runways
when they are still in good condition.  Applying this approach, about
26 percent of the runways in our database are at the point where
rehabilitation is appropriate, and within 10 years, this figure could
rise to more than 50 percent. 


--------------------
\1 We collected detailed PCI data from about 35 percent of the
airports eligible for federal funding and used these data to create
our database.  The remaining 65 percent of the eligible airports did
not have PCI data available (or was unusable), and we predicted their
condition by using a model based on other airport characteristics. 
Our approach, which is explained in further detail in app.  I, was to
use the section-by-section PCI information contained in our database
to create weighted average PCI ratings for entire runways, weighing
by section area. 


   CURRENT RUNWAY CONDITIONS ARE
   GENERALLY GOOD
---------------------------------------------------------- Chapter 2:1

Overall, the PCI ratings for the runways in our database were good to
excellent in 1998 (see fig.  2.1).\2 About 77 percent of all runways
were within the categories of "good," "very good," and "excellent."
The rest were divided between "fair" and "poor" and lower, as shown
in figure 2.1. 

   Figure 2.1:  Classification of
   PCI Scores for Runways at 1,154
   National System Airports in
   1998

   (See figure in printed
   edition.)

Source:  GAO's analysis of PCI data.  See app.  I for a more detailed
description. 

To determine if the condition of runways at airports without detailed
PCI data was likely to differ substantially from the condition of
runways with usable PCI data, we developed a model using
characteristics that tended to be predictive of conditions at
airports with PCI data (see app.  I for more detailed information). 
Our analysis of the two groups showed that they were similar in terms
of the type and age of runway pavements, the size and volume of
airports, past and planned future spending, and the type of
climate.\3

We analyzed the relationship between the weighted average runway PCI
scores and various airport characteristics, and used the results to
estimate PCI ratings for runways at airports that did not have PCI
data.\4

Predicted ratings for airports without PCI data showed that about 80
percent of the runways were in the categories of "excellent," "very
good," and "good" (see fig.  2.2).  The distribution is similar to
weighted average runway ratings, discussed earlier, at airports that
had PCI data (see fig.  2.1). 

   Figure 2.2:  Estimated Runway
   PCI Ratings for Airports
   Without PCI Data, 1998

   (See figure in printed
   edition.)

Note:  These are estimated PCI ratings we developed for illustrative
purposes, not ratings based on actual PCI data collected at these
airports.  See app.  I for an explanation of how we derived the
estimates. 

Source:  GAO's analysis. 


--------------------
\2 Our database contained information on runway pavement condition
for 1,154 airports.  These airports had 1,647 runways.  We were not
able to include data for 520 airports with PCI ratings because of
various difficulties, such as problems with the PCI software,
incomplete or inconsistently assembled information, data generated
prior to 1990, and data entry errors.  App.  I, which explains our
methodology, discusses these problems in further detail. 

\3 While there are 2,177 airports in the non-PCI group, our analysis
is restricted to 1,705 airports.  We eliminated 299 airports for one
of several reasons--the airport does not exist (is planned or had
closed) or is outside of the continental United States.  An
additional 173 airports were eliminated from our analysis because of
insufficient data. 

\4 Our approach is explained in further detail in app.  I. 


   OVER THE NEXT 10 YEARS, MANY
   RUNWAYS WILL NEED
   REHABILITATION
---------------------------------------------------------- Chapter 2:2

Although most runways have favorable PCI scores, many will need
rehabilitation--including the rehabilitation of pavement that may
still be in good condition--within the next 10 years.  About 26
percent of the runways in our database were at or below the relevant
critical threshold, meaning that they had already reached (or passed)
the most cost-effective point for rehabilitation.  Of the airports in
our database, 361, or 31 percent, had at least one runway that had
already reached this point. 

If rehabilitation is done on pavement before it deteriorates
substantially, the pavement's useful life can be extended with
methods that are not as expensive--for example, with a thick overlay
rather than with complete rebuilding.  For airports that use the PCI
approach, the point at which rehabilitation can be done most
cost-effectively is referred to as the "critical PCI." For small
airports (general aviation and commercial airports not considered to
be hubs), this critical PCI is generally considered to be about 55,
which is the cutoff between "good" and "fair." For primary (large,
medium, small, and nonhub) airports, which must accommodate heavier
planes and greater traffic loads than small airports, the critical
PCI is often set at 65, which is considered "good" according to our
advisory panel.\5 As figure 2.3 shows, the percentage of runways that
were at or below the critical PCI of 65 at most categories of primary
airports was higher than the percentage of runways that were at or
below the critical PCI of 55 at small airports. 

   Figure 2.3:  Percentage of
   Runways at or Below Critical
   PCI for Runways at 1,154
   National System Airports in
   1998

   (See figure in printed
   edition.)

Source:  GAO's analysis of PCI data.  See app.  I for a more detailed
description. 

Figure 2.4 shows that, overall, 31 percent of the airports in our
database had at least one-third of their runways at or below the
critical PCI, ranging from 53 percent at nonhubs to 16 percent at
other commercial service airports.  Again, primary airports are
affected more than small airports. 

   Figure 2.4:  Percentage of
   Airports With at Least
   One-Third of Their Runways at
   or Below Critical PCI for
   Runways at 1,154 National
   System Airports in 1998

   (See figure in printed
   edition.)

Source:  GAO's analysis of PCI data. 

We predicted that about 26 percent of the airports that were not
included in the database had at least one-third of their runways at
or below the critical PCI, ranging from 50 percent at nonhubs to 7
percent at large hubs.  As with those airports in the database, the
primary airports not included in the database were affected more than
small airports not included in the database. 

We also projected the number of additional runways that are likely to
reach their critical PCI within the next 1 to 10 years.\6 As figure
2.5 shows, within 10 years, the number of runways that could reach
the point at which rehabilitation is appropriate could rise from 26
percent in 1998 to 50 percent in 2007.  Primary airports face the
prospect of a higher percentage of runways reaching their critical
PCI by 2007 than do small airports, in part because of the type and
amount of aircraft using runways at the primary airports. 

   Figure 2.5:  Number of Runways
   at or Below Critical PCI in
   1998 and 2007 for Runways at
   1,154 National System Airports

   (See figure in printed
   edition.)

Source:  GAO's analysis of PCI data. 


--------------------
\5 Some airports set an even higher threshold.  For example, Tulsa
International Airport expects its air carrier runways to have a PCI
of 70. 

\6 These PCI projections are based upon how similar pavement in
similar climates at similar airports deteriorates over time and
assumes that no major maintenance will occur during this period. 


NATION'S AIRPORTS WILL NEED TO
INCREASE SPENDING ON RUNWAY
REHABILITATION OVER NEXT 10 YEARS
============================================================ Chapter 3

Over the next 10 years, keeping runways at or above generally good
condition could require more money than is currently being spent for
runway rehabilitation systemwide.  We developed two estimates of
rehabilitation and preventive maintenance costs for those airports in
our database.\1 The first estimate of $1.38 billion over 10 years
assumed that these airports would have no budget restrictions and
could conduct rehabilitation and maintenance work before runway
pavement deteriorated to the point at which more expensive approaches
would have to be used.  However, these airports would need to spend
about $774 million in the first year--well beyond the historic level
of spending--if they chose to immediately undertake major
reconstruction of all runways that have begun to deteriorate rapidly. 
The second estimate, $1.62 billion over 10 years, assumes that
airports would have a fixed amount to spend on maintenance and
rehabilitation each year that is close to the actual amount
historically allocated through AIP for all airports.  Because
sufficient funding is not available to address the immediate need in
this scenario, many projects would have to be deferred, making them
more expensive.  As a result, even after spending more money in total
than under the first estimate, these airports would have $2.37
billion of unmet need. 


--------------------
\1 Our database represents 35 percent of those airports eligible for
federal funds.  The other 65 percent were not included in our
estimates. 


   COST OF REHABILITATING RUNWAYS
   DEPENDS HEAVILY ON HOW FAR THE
   PAVEMENT HAS DETERIORATED
---------------------------------------------------------- Chapter 3:1

The cost of preventive maintenance and rehabilitation work on airport
runways depends heavily on airports' decisions about when to do the
work.  As figure 3.1 shows, the typical runway pavement will
deteriorate from excellent to poor condition over time--usually a
gradual decline at first, followed by a steep decline later. 

   Figure 3.1:  Conceptual
   Illustration of Pavement
   Condition Life-Cycle

   (See figure in printed
   edition.)

Source:  Adapted from M.Y.  Shahin, Pavement Management of Airports,
Roads, and Parking Lots (New York, NY:  Chapman & Hall, 1994). 

For the PCI-based pavement management system we used in this
analysis, the point at which rehabilitation can be done before the
steep decline occurs is called the critical PCI (explained in ch. 
2)--set at 65 for primary airports and 55 for nonprimary airports. 
If the work is done before deterioration accelerates, the cost of
rehabilitation can be reduced.  For example, an examination of the
deterioration rates of runway pavements at general aviation airports
in a northwestern state showed the total reconstruction of the
runways could be required when the pavements were about 28 years old
and had a PCI of 30, at a cost of $20 a square yard.  However, if the
airports chose to apply slurry seal coats every 10 years at a PCI
slightly higher than the critical PCI, the PCI would rise 10 points
with each application, at a cost of $2.25 a square yard.  In this
scenario, the airports would apply three slurry seal coats in 30
years at a total cost of $6.75 a square yard, obtaining a PCI between
70 and 80, instead of reconstructing a runway in 30 years, at a cost
of $20 a square yard to obtain a PCI of 100.\2 In another example, an
examination of the deterioration rate of a runway at a medium hub
airport in the Southwest showed that total reconstruction could be
required at 20 years, at a PCI of 30, at a cost of about $45 a square
yard.  However, if the airport chose to overlay the runway every 11
years, when the pavement reached the critical PCI of 65, the cost
would be $19 a square yard.  Over a 40-year period, the airport would
either totally reconstruct the runway twice at a total cost of $90 a
square yard or overlay it 2.5 times, at a total cost of $47.50 a
square yard, with the same effect of resetting the PCI to 100. 


--------------------
\2 To obtain additional information on maintenance and rehabilitation
costs, see app.  I. 


   FOR THE 1,154 AIRPORTS STUDIED,
   CONDUCTING MAINTENANCE AND
   REHABILITATION PROJECTS AT THE
   CRITICAL PCI POINT WOULD
   REQUIRE $1.38 BILLION OVER 10
   YEARS
---------------------------------------------------------- Chapter 3:2

Our analysis shows that to keep the runways in our database in
generally good condition by maintaining and rehabilitating runways as
they reach their critical PCI, the 1,154 airports would need to spend
about $1.38 billion over the next 10 years.\3 About 28 percent of the
funding need under this scenario would be for primary airports and 72
percent for small airports (see table 3.1).  Among individual airport
categories, the largest need was for projects at general aviation
airports, followed by nonhub airports. 



                               Table 3.1
                
                Cost to Maintain and Rehabilitate 1,154
                National System Airports--First Scenario

                         (Dollars in millions)

                                                       Maintenance and
                                                        rehabilitation
Airport type                    Number of airports               costs
------------------------------  ------------------  ------------------
Small airports
----------------------------------------------------------------------
General aviation                             1,005                $989
Other commercial service                        19                  14

Primary airports
----------------------------------------------------------------------
Large hub                                       14                  66
Medium hub                                      17                  86
Small hub                                       19                  29
Nonhub                                          80                 200
======================================================================
Total                                        1,154              $1,384
----------------------------------------------------------------------
Note:  We made several key assumptions for the first scenario. 
First, we assumed that the critical PCI that would serve as the
trigger for conducting rehabilitation work would be 55 for small
airports (general aviation and other commercial service) and 65 for
primary airports (large, medium, small, and nonhub).  Second, we
assumed that the estimated costs would include maintenance projects
(such as crack-sealing or joint resealing) done to help keep
pavements from reaching their critical PCI for as long as possible. 
Third, we assumed that funding for all projects would be available
when the PCI reached the critical point.  This meant, for example,
that almost $774 million of the total would be spent in the first
year, because many runways are currently below their critical
PCI--which makes them more expensive to repair than if they were at
or above the critical PCI.  Although this funding assumption may not
reflect the reality of individual airports' actual funding
constraints, it does provide the most accurate estimate of funding
needs.  Finally, we assumed that inflation would increase costs by
2.4 percent per year. 

In this scenario, about 89 percent of the total funding is used for
rehabilitation work, while the remaining 11 percent would be needed
for maintenance, such as crack-sealing, seal coats, or thin overlays. 

The needs of 1,154 airports with PCI data are not necessarily
representative of all 3,331 airports in the national system, either
in the total amount of money needed or in the distribution of this
money between types of airports.  Because the size of the group that
could not be analyzed is so great, it is likely that the need for
rehabilitation funds for all the airports in the system is
considerably higher than the amount we could identify.  Similarly,
because general aviation airports constitute more than 84 percent of
all airports in the national airport system, they would likely have a
considerable portion of total funding needs. 


--------------------
\3 As explained in ch.  2 , we expanded our analysis of runway
conditions beyond this subgroup of national system airports. 
However, we cannot use this same approach to make reliable
projections about how much it is likely to cost to rehabilitate and
maintain runways throughout the national airport system.  The
pavement management software used to project pavement costs requires
detailed information, including specific distress data and other
section data, provided by PCI ratings or some similarly detailed
approach. 


   AT CURRENT FUNDING LEVELS,
   REHABILITATION PROJECTS AT SOME
   OF THE 1,154 AIRPORTS WOULD GO
   UNMET, AND COSTS WOULD
   EVENTUALLY RISE
---------------------------------------------------------- Chapter 3:3

Although the first scenario assumes that every runway will be
maintained or rehabilitated at least cost--when it reaches its
critical PCI--this assumption does not reflect recent funding
experience.  For the projects to be done at the least cost, more than
half of the $1.38 billion needed under this scenario, $744 million,
would need to be spent in the first year.  However, if funding
availability more closely matches spending in recent years,
expenditures on runway rehabilitation would be only a fraction of
that amount in that year.  This means that some projects are likely
to go unfunded by AIP, resulting in airports needing either to find
alternative financing sources or to delay projects and increase their
eventual cost. 

While there is no reliable, complete information about how much
airports currently spend on runways, an FAA headquarters official
indicated that for most airports, AIP funds were the largest source
of funding for runway rehabilitation projects.  Since 1982, FAA has
allocated over $2.2 billion through AIP for runway rehabilitation and
eligible runway maintenance projects. 

We conducted another analysis of our PCI database, this time using
$162 million per year as the maximum funding available, to provide
some indication of what was likely to occur at funding levels that
were more likely to reflect current spending levels.\4 In this second
estimate, airports in our database would spend a total of $1.62
billion over 10 years.\5

Primary airports would receive about 42 percent of the funding, while
small airports would receive about 58 percent (see table 3.2). 



                               Table 3.2
                
                Cost to Maintain and Rehabilitate 1,154
                    National System Airports--Second
                                Scenario

                         (Dollars in millions)

                                                       Maintenance and
                                                        rehabilitation
Airport type                    Number of airports               costs
------------------------------  ------------------  ------------------
Small Airports
----------------------------------------------------------------------
General aviation                             1,005                $928
Other commercial service                        19                  11

Primary airports
----------------------------------------------------------------------
Large hub                                       14                  88
Medium hub                                      17                 141
Small hub                                       19                 104
Nonhub                                          80                 345
======================================================================
Total                                        1,154              $1,620
----------------------------------------------------------------------
Note:  We made several key assumptions for the second scenario. 
First, each year's funding was divided among the various airport
types according to the pattern of AIP allocations in recent years. 
For example, general aviation airports have typically received 26
percent of AIP funds, so we allocated 26 percent of the $162 million
to these airports.  If a particular type of airport did not need the
entire allocation, we reallocated the remaining amounts to airport
types that still had unmet needs.  Second, the point at which a
runway section would become eligible for rehabilitation funding would
be the same as in the first scenario--when it reached the critical
PCI of 65 for primary airports or 55 for small airports.  We also
assumed that inflation would increase costs by 2.4 percent per year. 
Projects were ranked by priority, and if a project was not ranked
highly enough to qualify, less expensive maintenance procedures were
applied and funding availability was reexamined in future years. 
However, if the pavement deteriorated to such a point that
maintenance projects could no longer extend the life of the pavement,
then no funds would be applied to the section until rehabilitation
funds were available. 

In the second scenario, the percentage of funding devoted to
rehabilitation increases to 92 percent, while the percentage for
maintenance decreases to 8 percent. 

The $1.62 billion in future spending in the second estimate does not
pay for the same number of projects as the $1.38 billion in the first
estimate.  Because of the dramatic cost increases that occur when
rehabilitation is deferred past the critical PCI, the additional $233
million would not be enough to meet total need.\6 Two categories of
airports--general aviation and nonhubs--would have unmet needs
totaling $2.37 billion over the 10-year period.\7 Because this
estimate is based on these 1,154 airports spending an amount that is
likely to reflect what all airports in the national airport system
are currently spending, it probably understates the unmet need. 

The amount of rehabilitation that could be accomplished in the first
estimate exceeds that of the second estimate even when each option is
restated in present value terms.\8

Present value analysis reduces the difference between the two
estimates because more of the second estimate's costs is incurred in
later years and is more heavily discounted.  Even so, the first
estimate is still somewhat less expensive ($1.22 billion versus $1.29
billion, respectively).  That is, the present value savings resulting
from spending money later do not fully offset the cost increase
resulting from greater deterioration.  In addition, our present value
analysis did not consider the $2.37 billion in projects left unfunded
by the second scenario. 

The potential lack of funding in the second estimate could have the
greatest implications for small airports.  Small airports have a more
difficult time getting access to alternative financing resources and
therefore may have little choice but to rely heavily on AIP grants. 
Primary airports, which have a greater availability to tap into other
sources of funding, such as bonds or passenger facility charges, may
have more flexibility in this regard. 

This is not to say that airports will definitely face a funding
shortfall for their rehabilitation and maintenance projects or that
more pavement will fail than has historically been the case. 
However, the potential for airports to be somewhat at risk heightens
the need for FAA to have a mechanism in place for determining how
best to decide which airports should receive grants for runway
rehabilitation and eligible maintenance.  In chapter 4, we examine
FAA's current approach for making such decisions. 


--------------------
\4 Since we could not predict how FAA would allocate future AIP
funding, we elected to average the total amount of AIP allocated to
rehabilitation and maintenance of runways over the past 16 years and
apply the entire amount to the airports in our database.  The $162
million represents the average AIP funds allocated to runway
rehabilitation and maintenance projects and the "share" that airports
would apply to the grant.  Our total probably overstates the amount
these airports collectively spend on runway rehabilitation, because
the average represents funds expended at all of the 3,331 eligible
airports.  Nonetheless, in the absence of better data, doing so
provides a reasonable point of comparison against our first estimate. 

\5 Because inflation is built into both this cost estimate and the
first scenario, the estimates of the amounts that would be spent are
in nominal, rather than constant, dollars.  That is, they allow the
cost of rehabilitation to rise over time, not just because
deterioration gets worse but also because of inflation. 

\6 In addition, when rehabilitation is deferred, inflation adds to
the nominal cost and reduces the amount of runway rehabilitation that
can be done for a given nominal expenditure. 

\7 For general aviation airports in our database, the unmet need
would be $1.901 billion over the 10-year period; for nonhub airports,
the unmet need would be $469 million over the same period. 

\8 Present value analysis removes the influence of inflation and
accounts for the time value of money by discounting the future cost
of investment by a discount rate equal to the government cost of
funds.  We used a 5.9-percent discount rate for our analysis because
that was the approximate interest rate for long-term government bonds
in May 1998, when we did this analysis. 


REVISED APPROACH FOR EVALUATING
THE TIMING OF RUNWAY PROJECTS
COULD HELP STRETCH AIRPORT AID
============================================================ Chapter 4

The substantial estimated funding need described in chapter 3 raises
questions about what, if anything, FAA should do to ensure that AIP
funding for runways is spent as wisely and effectively as possible. 
FAA's system for determining which projects should get funding first
gives runway-related projects higher priority than most other types
of projects, thus enhancing their likelihood of funding.  However,
this system does not formally consider the timing of maintenance and
rehabilitation projects--factors that pavement experts say can
maintain good pavement condition at the least cost.  We developed
several options that could be explored for doing so.  They involve
either improving the information that FAA inspectors collect as part
of their annual visits to airports or obtaining independent PCI
ratings from airports. 


   HIGH PRIORITY OF RUNWAY
   REHABILITATION PROJECTS HELPS
   ENSURE AIP FUNDING
---------------------------------------------------------- Chapter 4:1

The National Priority System is FAA's primary method for determining
which airport projects should receive discretionary AIP funding.\1
Historically, the demand for discretionary funds has exceeded the
amount available for distribution.  The system provides a way for FAA
to evaluate, in a standardized manner, which projects should receive
initial consideration for funding. 

FAA officials said when projects are put in priority order using the
National Priority System, the rankings of runway rehabilitation
projects have historically been high enough to qualify them for
funding.  FAA headquarters officials also said that most runway
rehabilitation projects contained in FAA's 5-year Capital Improvement
Plan (CIP) receive funding.  However, they added that local FAA
officials screen projects for inclusion in the CIP and limit the list
according to the funding levels anticipated for each year.  While the
local FAA screening process may include factors such as a review of a
runway's PCI, there is no formal mechanism in place at the national
level to determine (1) whether it is the most cost-effective time to
rehabilitate the runway given the pavement's projected deterioration
and (2) whether the runway in one FAA jurisdiction is more
time-critical to rehabilitate than a runway in another jurisdiction. 
Therefore, while it may appear that all runway rehabilitation
projects are funded each year, it is likely that there is some unmet
need that is not captured in FAA's current process for setting
priorities. 


--------------------
\1 In their initial screening of projects, most FAA field offices
sometimes consider some additional factors in recommending which
applications to send forward for headquarters approval.  One of these
factors, PCI ratings, is discussed later in this chapter. 


   FAA'S CURRENT SELECTION
   APPROACH IS NOT GEARED TOWARD
   LIFE-CYCLE PAVEMENT MANAGEMENT
---------------------------------------------------------- Chapter 4:2

Because it appears that runway rehabilitation projects currently fare
well in the competition for discretionary grants at the national
level, FAA has not formally acknowledged the need to choose among
them--that is, to decide which rehabilitation projects should be
placed ahead of others.  Should this need arise, FAA has no way to
determine which projects should be funded.  Ranking projects might be
necessary if, for example, overall funding levels dropped, there was
a heavy influx of applications for even higher-priority projects, or
a delay in funding projects occurred that caused the potential
funding gap identified in chapter 3 to materialize. 

There is another more important reason for FAA to examine its process
for evaluating runway projects:  the current process does not provide
FAA with a means of evaluating whether the proposed project
contributes the maximum possible benefit toward extending the life of
the runway pavement.  As discussed in chapter 3, FAA and pavement
management experts believe that the most cost-effective way to manage
a pavement system is to maintain or rehabilitate it at a critical
point, before relatively rapid deterioration sets in.  (See fig. 
3.1.)

A pavement management approach that selects maintenance and
rehabilitation projects at critical times makes the maximum use of
the total dollars invested to build the runway and keep it
serviceable.  For example, as figure 4.1 shows, an appropriate
rehabilitation project (such as a major pavement overlay) before the
pavement begins to deteriorate can significantly add years to its
life.  Adding an effective preventive maintenance program, such as
sealing pavement cracks on a regular basis, is likely to lengthen the
life even more.\2 The cost of doing such activities at the
appropriate time is more than repaid by being able to wait longer to
replace the runway. 

   Figure 4.1:  The Effect of
   Different Rehabilitation and
   Maintenance Scenarios on the
   Life-Cycle of an Asphalt Runway

   (See figure in printed
   edition.)

Note:  The examples shown here are hypothetical.  Actual pavement
life and the timing of rehabilitation projects also depend on other
factors, such as climate and the amount of use. 


--------------------
\2 The Congress has recognized the importance of maintenance in
lengthening pavement life and (since 1995) has required airports to
have a management program for pavement maintenance in place as a
condition of receiving AIP funds for pavement replacement or
reconstruction.  At present, however, there is no specific
requirement other than that the airport owner assure FAA that a
maintenance program is in place.  The Congress also approved a pilot
maintenance program, allowing airports to use AIP funds for pavement
maintenance projects currently not eligible for AIP funds.  (See ch. 
5 for more information on the program.)


      LACK OF DATA IMPAIRS FAA'S
      DECISION-MAKING
-------------------------------------------------------- Chapter 4:2.1

FAA's current process for evaluating runway rehabilitation proposals
does not include an evaluation of information from the perspective of
critical times for maintenance or rehabilitation at the national
level, and airports are currently not required to have PCI data for
their runways for such an assessment at the local level.  As a
result, FAA is not in a position to determine which projects are
being proposed at the most economical point in time, as represented
by the critical PCI range.  Having such information would allow FAA
and airports to know when to plan runway rehabilitation at the most
cost-effective times.  This, in turn, would help maximize the
federal, state, and local investment in runways. 

FAA has some information on runway surface conditions (collected as
part of its Airport Safety Data Program) for each airport in the
country.  However, the data are based on pavement evaluations that
are not rigorous or specific enough to be used as a pavement
management tool.  The collection of information on runway conditions
represents a minor part of the overall inspection conducted under the
Airport Safety Data Program--a quick rating of pavements as "good,"
"fair," or "poor." The inspectors who assign these ratings generally
have limited training in this aspect of the inspection, and the
rating criteria they use are vague and focus only on cracks, omitting
other types of pavement distresses.  FAA officials and state
inspectors said that the pavement rating was not intended to provide
the same information as the PCI and should not be used to assess the
condition of individual runway pavements. 

PCI ratings would provide far more specific information that would
enable airports and FAA to take a more proactive approach toward
pavement management.  However, these ratings are currently available
only for less than half of the airports in the national airport
system, and even for these airports, some are unusable.  Moreover,
FAA currently does not systematically collect such data from
airports.  Furthermore, available PCI data would require considerable
work before the information is fully comparable from airport to
airport. 


   OPTIONS FOR DEVELOPING A
   LIFE-CYCLE APPROACH
---------------------------------------------------------- Chapter 4:3

In consultation with our advisory panel, airport officials, and FAA,
we identified three options that would help to improve the
information available to FAA on the condition of runway pavement: 
(1) improving the existing database, (2) using PCI information on a
limited basis to help evaluate airport master plans and individual
projects, and (3) creating a PCI database that would allow FAA to
become more proactive in managing runway grants.  The actions that
would have to taken under each of these options are discussed below. 


      OPTION 1:  STRENGTHEN THE
      PAVEMENT PORTION OF FAA
      INSPECTORS' AIRPORT REVIEWS
-------------------------------------------------------- Chapter 4:3.1

To improve the information on airport runway conditions it collects
during its inspections for the Airport Safety Data Program, FAA would
have to take such actions as developing sufficient rating criteria
and providing more updated guidance for inspectors.  The current
rating criteria are vague (i.e., good, fair, poor) and require
substantial interpretation by inspectors.  For example, state
officials in 9 of the 10 states we visited told us they had developed
their own interpretation of the criteria, as well as adding other
evaluative factors on their own, such as the quality of the ride,
color of the asphalt, presence of vegetation or foreign debris, and
type of distress present in the pavement.  There appears to be little
consistency among the states.  As a result, pavements in similar
conditions in different states could be rated differently.  For
example, one state inspector said that he was trained so that he
"should be able to determine what good and poor pavements are--fair
is everything in between," while in another state, the inspector said
that determining what is a fair pavement is the hardest task. 

The variance in interpretation may be further exacerbated by the
minimal training inspectors receive in evaluating runway pavement
conditions.  The analysis of pavement conditions receives little
attention in the instruction provided through the safety inspection
classes funded by FAA.  At the same time, inspectors we interviewed
said they are not expected to spend much time evaluating pavement
during inspection because the inspection focuses on other safety
aspects of the airport, such as measuring runway obstructions and
noting physical changes to the airport.  To the extent that these
pavement evaluations would require additional time from inspectors,
FAA would also need to determine how to make additional time
available or what other portions of the inspection might be reduced
to make up the difference. 

Improving the existing rating approach would give FAA additional
information for managing runway grants, but this approach would also
carry some limitations.  An improved rating system would give FAA a
better tool for understanding the general condition of runways
nationwide and for assessing the merits of individual runway
projects.  However, because the system would still lack the rigor of
a more structured approach, such as the PCI, FAA probably would not
be able to project runway conditions into the future or to estimate
the likely costs involved in keeping runways in reasonable condition. 


      OPTION 2:  REQUIRE AIRPORTS
      TO SUBMIT PCI DATA WITH
      AIRPORT MASTER PLANS OR
      PROJECT APPLICATIONS
-------------------------------------------------------- Chapter 4:3.2

Airports could be required to submit PCI data to FAA to better
determine their needs for maintenance and rehabilitation funds for
their runways.  PCI ratings could be included as part of an airport's
development planning process as well as be submitted to FAA as part
of a package of information used in applications for runway grants. 
About 35 percent of all airports in the national airport system
currently have PCI ratings usable for this purpose.  Although federal
law currently requires airports to have a maintenance management
system as a condition of receiving AIP funding for pavement
replacement or reconstruction, this requirement does not specify that
the system include a PCI.  General aviation airports, which account
for the majority of airports in the national airport system by far,
constitute 1,762 of the airports that are not in our database.  The
cost for most general aviation airports to have an engineer develop a
PCI is likely to be about $2,500 to $3,500, according to a consultant
who conducts such evaluations.  Large commercial service airports,
which generally have more complex runway systems and construction
histories, will face a higher cost.  This consultant indicated that
to ensure reasonable accuracy, a PCI would generally need to be
conducted about every 3 years.  Several software packages are
available for compiling the information and projecting future runway
conditions and costs. 

With this option, much of the effort to develop detailed information
on the condition of runway pavement shifts to the airports.  Instead
of FAA's developing an improved rating system and administering a
nationwide database, airports themselves would obtain a PCI analysis
and make it available to FAA.  If FAA were to ask airports to submit
PCI information with their airport master plans or grant
applications, it would have a sound basis to evaluate whether future
proposed projects were appropriate for the situation and being
proposed at the right time.  We did find evidence that FAA field
offices were already doing this kind of evaluation when such
information was available.  FAA officials at 22 of the 23 airport
district and other field offices we surveyed said they use PCI data,
when available, in considering which proposals should be submitted to
FAA headquarters for formal review.  Headquarters officials said they
are aware of such applications of PCI data, but because the
availability of PCI data is spotty, this kind of evaluation is now
being done only on an ad hoc basis.  Adopting this option would mean
incorporating PCI data into the evaluation process as a standard way
of doing business. 

We found that more airports are interested in developing PCI
information, perhaps using AIP grant money to do so.  During our
review, a number of states and airports obtained AIP grants to
conduct a PCI analysis for their airports or expressed their
intention to do so.  Some states told us that FAA has offered AIP
grants to obtain PCI ratings for the airports in the states' system
plans. 


      OPTION 3:  OBTAIN PCI DATA
      FROM ALL AIRPORTS AND CHANGE
      THE GRANT MANAGEMENT
      APPROACH
-------------------------------------------------------- Chapter 4:3.3

Obtaining PCI data from all airports would offer FAA a unique
opportunity to move dramatically from a reactive to a proactive role
in managing grants for pavement maintenance or rehabilitation. 
Because PCI data can be used to forecast pavement conditions--and
therefore to determine in advance when maintenance and rehabilitation
can be done most cost-effectively--this option would give FAA
information previously unavailable for ensuring that AIP dollars are
spent as wisely as possible.  Using PCI information, FAA would be
able to develop a better sense of how much rehabilitation and
maintenance expenditures were likely to cost several years in the
future.\3 Even more important, the information would give FAA the
opportunity to alert airports to upcoming opportunities for
conducting runway rehabilitation and maintenance projects at times
that promise the greatest payout for the dollars expended.  Under the
existing system, FAA must wait for airports to come to it with
project proposals.  With PCI information, FAA would be able to
foresee needs rather than react to requests. 

This option differs from the previous one in the degree to which FAA
would be obtaining PCI information and creating a database from it. 
In option 2, airports would submit PCI data as part of their airport
master plan or AIP grant applications.  Under this third option, FAA
would obtain PCI data from all airports, whether they were submitting
pavement-related AIP grant applications or not.  FAA would also be
combining the information from individual airports into a systemwide
database that would produce forecasts about future needs and costs. 

FAA would face a considerable effort in ensuring that PCI information
could become a useful database.  As we found from our efforts to
analyze PCI information, the presence of PCI data at one airport was
no guarantee that this information could be combined with data at
other airports.  Airports use different software packages to catalog
and analyze PCI data, and the software packages are not compatible. 
As discussed in chapter 2, we used one type of pavement management
software; however, hundreds of airports have used one of several
proprietary software packages that often do not provide an easily
accessible computer link to other software packages.  In developing
our database of PCI information, for example, we had to exclude many
airports that had PCIs because we could not use their computerized
data. 

To some extent, FAA itself has fostered the development of
proprietary systems.  Over the years, FAA has awarded many grants to
states or airports for the development of planning systems.  One
outgrowth of these grants has been stand-alone information systems
that differ enough from other systems to make comparisons difficult
or impossible.  Acknowledging a benefit in creating crosswalks
between databases, one company is developing software to provide a
feasible way to translate data from one software package in and out
of its own proprietary software.  The developers of one of the other
software packages are developing similar techniques.  It is unclear
if other companies will follow suit. 


--------------------
\3 FAA has some indication of these costs through its current system,
in that airports are required to submit anticipated projects in
advance of actually applying for AIP grants.  FAA requires airports,
through their planning process, to identify individual projects for
funding consideration.  The NPIAS database includes individual
airport projects from approved airport master plans, system plans,
and discussions with airport officials, and it shows this planned
development for up to 10 years into the future. 


   CONCLUSION
---------------------------------------------------------- Chapter 4:4

While runway rehabilitation projects currently fare well in the
competition for AIP funding, evaluating whether improvements are
needed in the process for considering them is important for several
reasons.  First, if AIP funding levels should drop, or if the demand
for even higher-priority projects should increase, FAA has no
objective means to determine which applications for rehabilitation
projects will do the most to extend pavement life for the dollars
expended.  Second, if AIP funds are not spent as effectively as
possible on runway projects, less money is available to fund other
important but lower-priority projects. 

Timing is key in making the dollars spent on rehabilitation projects
work the hardest, many experts agree.  For example, two airports--one
with moderately deteriorated runways, the other with runways in much
worse condition--may both need rehabilitation projects, but the
project at the airport with runways in better shape is likely to cost
only a fraction of the cost of the other airport's project. 
Information about pavement conditions, in turn, is key to knowing the
opportune times to conduct such work.  FAA's current information is
not adequate for making such judgments, nor does FAA require airports
to develop such information in developing their airport master plans
or project applications.  While we have concentrated our work on
runways, it should be noted that the situation is similar with regard
to projects for taxiways and aprons.  A better information system
could affect all three types of pavement projects. 

To develop better information, FAA could improve its existing
information on runway condition or rely on airports to develop PCI
data.  Of these two approaches, using PCI information would give
airports and FAA more flexibility in managing airport development. 
Because of the rigor of the PCI approach and the ability to project
this information into the future, a PCI database would give FAA the
opportunity to manage the grant program more proactively--to
anticipate runway project needs and work with airports to ensure that
projects were proposed and developed at the most opportune times. 


   RECOMMENDATION
---------------------------------------------------------- Chapter 4:5

To enable FAA to make the most cost-effective decisions when awarding
Airport Improvement Program grants for runway rehabilitation
projects, GAO recommends that the Secretary of Transportation direct
the Administrator of FAA to evaluate options for improving the
quality of information on airfield pavement conditions for national
system airports.  These options include, but are not limited to,

  -- improving the existing runway condition information contained in
     the Airport Safety Data Program by reviewing and revising rating
     criteria, and providing adequate training for inspectors;

  -- requiring airports to submit PCI information as part of their
     airport master plan or as support in applications for relevant
     discretionary AIP grants; or

  -- requiring all airports in the national airport system to submit
     PCI information on a regular basis and using this information to
     create a pavement condition database that could be used in
     evaluating the cost-effectiveness of project applications and
     forecasting anticipated pavement needs. 


   AGENCY COMMENTS
---------------------------------------------------------- Chapter 4:6

FAA said that it would consider the options for developing a
life-cycle approach to pavement management as outlined in our
recommendation. 


PARTICIPATION IN PAVEMENT
MAINTENANCE PILOT IS LIMITED
============================================================ Chapter 5

The Congress, in 1996, authorized FAA to use AIP funds for up to 10
pilot projects for pavement maintenance at nonprimary airports, but
interest in participating in this program has been limited.  FAA
awarded grants to three states and one airport owner in fiscal year
1997.  We contacted every state to determine why so few had applied. 
Their responses ranged from not having enough time or staff to apply
to having their own programs to pay for such work.  At the same time,
however, two states and one airport owner that received grants in
fiscal year 1997 told us they could not have financed maintenance at
general aviation airports without the grants.  Given the experience
with the pilot program to date, if the Congress wishes to let the
states and airports apply for grants that cover stand-alone
crack-sealing projects, the most efficient approach may now be to
forgo the pilot program and add stand-alone crack-sealing to the list
of eligible AIP projects. 


   FEW STATES OR AIRPORT OWNERS
   EXPRESSED INTEREST
---------------------------------------------------------- Chapter 5:1

Under current law and FAA rules, crack-sealing as a stand-alone
project is not eligible for AIP funding.\1 The pilot program allowed
for expanded eligibility, but only 14 states or airport owners had
expressed interest in it as of October 1997.  In May 1997, FAA
selected five states and one airport owner as candidates for pilot
projects.  These candidates were expected to negotiate project costs
with FAA and provide supporting information leading to a grant
application.  As of December 1997, FAA had awarded grants to three
states and one airport owner.\2

According to our September 1997 survey of the 50 state aviation
departments, 10 states asked to be considered for stand-alone
crack-sealing projects:  Alabama, Alaska, Colorado, Louisiana, New
Hampshire, New Jersey, Pennsylvania, Texas, Vermont, and Virginia. 
In May 1997, FAA announced the selection of Alabama, Louisiana, New
Hampshire, Texas, and Vermont as candidates for pilot grants.\3 The
selected airports met the program's criteria because they were
nonprimary airports; and the three states, Alabama, New Hampshire,
and Vermont, had no medium or large hubs, a requirement for at least
some of the projects receiving funds.  Of the candidate states, only
Texas funds crack-sealing and other airfield maintenance at its
general aviation airports.  Among individual airport owners, four
airport owners asked to be considered:  the Port of Portland, Oregon;
the state of New York for its Republic Airport in Niagara Falls, New
York; and the city of Butte, Montana.  The Port of Portland was
subsequently selected as the only airport owner candidate. 

As of December 1997, FAA had awarded four grants totaling
$566,018--three to states (Alabama, New Hampshire, and Vermont) and
one to the Port of Portland--for maintenance work at 24 airports. 
The four awardees all plan to conduct, or have conducted, projects
that include certain other types of maintenance, such as seal
coating, that were already eligible for AIP funding.  Table 5.1
summarizes the grant amounts, number of airports covered, and types
of maintenance planned and completed. 



                               Table 5.1
                
                  Projects Planned by Fiscal Year 1997
                    Maintenance Pilot Grant Awardees

Awa
rde                   Number of
e    Grant amount      airports  Maintenance projects
---  ------------  ------------  -------------------------------------
Ala    $282,977\a             8  Crack sealing, seal coats, and
 ba                               patching
 ma
New     $83,041\b             5  Crack-sealing and seal coats
 Ha
 mp
 sh
 ir
 e
Por      $100,000             3  Crack-sealing and seal coats
 t
 of
 Po
 rt
 la
 nd
Ver    $100,000\c             8  Crack-sealing and seal coats
 mo
 nt
----------------------------------------------------------------------
\a Alabama's grant amount is high because it could not do all the
needed work with an allocation of just $25,000 per airport. 

\b New Hampshire has completed its projects and, as a result of cost
overruns, plans to request $89,473. 

\c Vermont believes its final costs will be $70,000 to $80,000. 

Sources:  Awardees. 


--------------------
\1 For the purposes of the pilot program, FAA also included pavement
patching and the cleaning of drainage systems as eligible maintenance
projects and said it would consider the eligibility of other
projects.  According to an FAA attorney, the determination not to
fund routine maintenance under the AIP program is a policy decision
based on statute.  In order to allow stand-alone crack-sealing
projects (other than the pilot program) to be funded, FAA would have
to modify its handbook and determine if legislation would also be
necessary. 

\2 All projects conducted under the pilot program are to be completed
by Sept.  30, 1999. 

\3 For various reasons, Texas decided to forgo participating in the
pilot.  Five other states (Alaska, Colorado, New Jersey,
Pennsylvania, and Virginia) did not participate for the following
reasons:  Alaska, because FAA determined that its needs were
primarily in the area of development rather than routine pavement
maintenance; Colorado, because it feared jeopardizing its state
maintenance funding and did not want to use its AIP funds that had
already been committed to projects; Virginia, because it did not wish
to use its state funds; New Jersey, because it did not provide
information to pursue the pilot maintenance program; and
Pennsylvania, because its original application was submitted as part
of a block grant proposal.  (For most states, FAA awards separate
grants to individual nonprimary airports, but block grant states
receive a single grant and administer it at the state level.) FAA has
asked Pennsylvania to resubmit its application separately from its
block grant. 


   GRANT AWARDEES SAID PROGRAM WAS
   IMPORTANT FOR MEETING
   MAINTENANCE NEEDS
---------------------------------------------------------- Chapter 5:2

Although few states or airport owners decided to participate in the
pilot program, the four that received grants in fiscal year 1997
indicated that the program was very important for conducting
maintenance at these small airports.  Alabama, Vermont, and Portland
officials we interviewed said they were pleased to be part of the
pilot program because they believed they could not have financed
maintenance at their general aviation airports in fiscal year 1997
without it.  A New Hampshire official noted that the program is
valuable in his state because the only other source of maintenance
dollars is the local airport owner. 

The pilot program will provide certain other benefits in addition to
those cited by grant recipients.  Pilot airports will have
maintenance management programs in place, and many will have pavement
performance data.  Pavement life will be extended as a result of the
pilot repair work and of the implementation of the maintenance
programs, and the technical data on pavement condition will help the
airports make better informed decisions about federal dollars needed
for any future pavement work. 

FAA planned to evaluate the success of the pilot program by
collecting data on maintenance performance from the participants but
has done little to ensure that it would receive such data from the
airports.  FAA promulgated guidelines noting that baseline surveys
should be available to evaluate the effectiveness of maintenance
practices and that airport owners would be required to inspect and
report on the effects of these pilot projects.  Most of the airports
participating in the pilot conducted PCI inspections to serve as
their baseline surveys.  However, in recent discussions with 1997
grant recipients under the pilot program, we learned that most of
them were not provided with specific guidance on completing either
the baseline surveys or the maintenance project reports. 


   PILOT PROGRAM PARTICIPATION
   LIMITED FOR VARIOUS REASONS
---------------------------------------------------------- Chapter 5:3

State officials responding to our September 1997 questionnaire cited
many reasons for not expressing interest in the pilot program, and
our recent discussions with FAA indicate that interest in the program
continues to be low.  We found no dominant reason for the lack of
interest in the program among the 40 states that did not apply.\4
Several reasons were related to some aspect of the application
procedure, such as the perception that the application period was
limited or the lack of staff to prepare an application.  Nonetheless,
problems related to the application process account for only a
portion of the reasons the program received few applicants.  Many
states that did not indicate a problem with the application process
also chose not to apply.  Their reasons for not applying included,
for example, the absence of additional money to fund the program, the
existence of their own maintenance programs, and some states'
statutory restrictions against applying. 

One reason we expected might be a key factor in decisions about
applying was whether a state's general aviation airports were
eligible to receive state-provided maintenance funding.  However, the
presence or absence of a state-funded maintenance program did not
predominate among the reasons cited by the states, and we found no
dramatic differences in the percentage of applications by the states
that had a state-funded program and those that did not.\5

In recent discussions with FAA officials administering the pilot
program for pavement maintenance, we learned that the expressed
interest from the airport community continues to be low.  Because of
this continuing lack of interest and because it believes that other
demonstration programs are more demanding on its resources and have
higher visibility, FAA has decided to focus more of its resources on
these other programs.  On April 24, 1998, FAA announced that six
states and airport owners had expressed interest in receiving pilot
program grants in fiscal year 1998 and that it had selected six
candidates.  As of June 15, 1998, FAA had awarded fiscal year 1998
pilot program grants, once again, to three of the fiscal year 1997
grant awardees, the states of Alabama and New Hampshire and the Port
of Portland, Oregon.  FAA intends to count any projects approved this
fiscal year toward the total of 10 projects that the Congress had
authorized for the program and award any remaining projects in fiscal
year 1999. 


--------------------
\4 Given the large number of airport owners in the national airport
system, we did not attempt to determine why owners did not apply. 
However, the FAA official administering the program speculated that
owners might have little interest because so few of them own more
than one airport. 

\5 Of the 34 states that have their own maintenance support program,
6 (17 percent) applied for the pilot program.  Of the 16 states that
do not have such a program, 4 applied (25 percent). 


   CONCLUSION
---------------------------------------------------------- Chapter 5:4

The limited response to the pilot program, while the result of many
factors, suggests that in the future only a few states and airport
owners may want to use AIP grants for crack-sealing and that more
states and airport owners would prefer to use AIP grants for capital
improvement projects.  If the response remains limited, a separately
administered pilot program may not be necessary to address the need
for crack-sealing.  FAA's evaluation efforts are unlikely to provide
much additional information for deciding whether to continue the
program because most participants were not told how to collect
performance data for FAA's analysis.  Because the pilot program in
effect makes crack-sealing--currently ineligible under AIP as a
stand-alone project--temporarily eligible for AIP funds, it may be
more efficient to simply add crack-sealing to the list of
AIP-eligible stand-alone projects.  Doing so would remove the need to
administer a separate program, and those states and airport owners
that might need AIP funds for maintenance assistance would have these
funds available through the regular federal funding process. 


   RECOMMENDATION
---------------------------------------------------------- Chapter 5:5

Because of the limited interest expressed to date in the pilot
program for pavement maintenance, we recommend that the Secretary of
Transportation direct the Administrator of FAA to review the need for
a separate pilot for airfield pavement maintenance.  To accommodate
applicants interested in using Airport Improvement Program funds for
stand-alone crack-sealing projects, the Administrator should
determine if it would be necessary to seek legislation before adding
stand-alone crack- sealing projects to the regular list of eligible
projects for the Airport Improvement Program. 


   AGENCY COMMENTS
---------------------------------------------------------- Chapter 5:6

FAA said that it agrees with this recommendation and will explore the
means to make crack-sealing eligible for funding under the Airport
Improvement Program. 


METHODOLOGY FOR ANALYZING RUNWAY
PAVEMENT CONDITIONS AND ASSOCIATED
COST
=========================================================== Appendix I

To determine the current condition of the nation's airport runways
and the funding levels needed to maintain and rehabilitate them over
the next 10 years, we solicited data from the Federal Aviation
Administration (FAA), individual airports, and state aviation
departments in an attempt to develop a database to examine pavement
condition.  About 35 percent of the airports in FAA's national
airport system had pavement condition index (PCI) information that
could be assembled into a database.  While PCI is the result of a
visual, not physical survey of airfield pavements, it was the only
pavement condition information broadly available in computerized
format for the purposes of our analysis.  Using available computer
software for pavement management, we analyzed the current and future
condition of runways at these airports and determined their future
cost requirements for maintenance and rehabilitation.  We were also
able to develop a model to predict current runway conditions at 65
percent of the airports without pavement condition information.  The
following sections discuss the development of the database, the
analysis of the database, and the process used to predict the current
condition of runway pavements for the runways at airports not
included in the database. 


   DEVELOPING PAVEMENT CONDITION
   INDEX DATABASE FOR AIRPORT
   RUNWAYS
--------------------------------------------------------- Appendix I:1

To develop the most comprehensive database possible, we sought
information from airports with PCI ratings.  To build the actual
database, we used software called MicroPAVER 4.0.\1 Although other
computer software exists for this purpose, we chose MicroPAVER 4.0
because more than half of the airports that provided PCI data
provided it in the MicroPAVER format, the FAA funded portions of its
development, and it is generally available to anyone at a minimal
cost. 

To build the database, we first solicited PCI data from commercial
airports, state aviation departments, and consultants who conduct PCI
inspections at airports.  In all, 1,710 airports submitted some type
of PCI information for inclusion in the database.  The data arrived
as (1) various versions of MicroPAVER software; (2) a format
requiring software called AIRPAV, a similar proprietary software
developed by Eckrose & Green, Inc.; (3) a format requiring software
called Decision Support System (DSS) developed by ERES, Inc.; and (4)
various other forms.  To combine these data formats, we performed the
following tasks: 

  -- MicroPAVER data:  1,017 airports submitted data in one of three
     MicroPAVER formats or in hard copy to be entered into the
     software.\2 We performed a records review of each data set
     submitted by an airport and found that 835 airports had
     submitted complete data sets.  We were not able to include data
     sets from 182 airports because their sets did not contain one of
     the following data elements:  runway information or the latest
     inspection date.  Complete data sets were all converted to
     MicroPAVER 4.0. 

  -- AIRPAV data:  393 airports submitted data in AIRPAV format. 
     After consultation with the developers of AIRPAV and MicroPAVER
     4.0 software, we were able to extract the necessary data fields
     from the AIRPAV file, reformat the data, and import the data
     into MicroPAVER 4.0.  We performed a records review of each
     airport's data and found that 141 airports had complete data
     sets usable in MicroPAVER 4.0.  We were not able to include 252
     airports' data because they did not contain one of the following
     data elements:  runway information, latest inspection date, slab
     length/width, or the amount or type of distress. 

  -- DSS data:  193 airports submitted data in DSS format.  We
     contracted with a company to translate and deliver airports'
     airfield pavement databases from this structure into MicroPAVER
     4.0.  The company was able to successfully translate all data
     for analysis, but we dropped 15 airports from the database
     because their information did not contain one of the following
     data elements:  runway information, latest inspection date, or
     slab length/width. 

  -- PCI Data in other formats:  71 airports submitted PCI data in a
     variety of formats not outlined above; none were included in the
     database.  Some of these airports used a pavement indexing
     system that varied significantly from the PCI guidance published
     by FAA.\3 Others submitted PCI data in hard copy, but we could
     not extrapolate enough data to manually enter the information
     into MicroPAVER 4.0. 

While we did not assess the validity of individual airports' data, we
did eliminate data that was incomplete (as discussed above) as we
created the database.  In total, we were able to use data from 1,154
airports, or about 35 percent of the 3,331 airports in FAA's national
airport system, and therefore able to apply for funds through the
Airport Improvement Program (AIP).  In all, these airports had 1,647
runways with 4,905 sections for purposes of a PCI analysis. 

In addition to the PCI data, we used several FAA databases to
ascertain other airport characteristics.  These databases included
data from FAA's AIP, Capital Improvement Plan (CIP), National Plan of
Integrated Airport Systems, Airport Safety Data (5010), and aircraft
operations.  We did not audit the accuracy of these databases but did
perform some limited cross-checking of information to assess their
reasonableness.  We developed a climate database derived from a
climate map developed by Professor Samuel Carpenter, University of
Illinois.  The map contained data for the continental United States
and thus confined our analysis to 3,000 airports.  The climate data
were traced to the source.  We also used state maintenance
information derived from our survey work in chapter 5. 


--------------------
\1 MicroPAVER 4.0 was developed by the U.S.  Army Construction
Engineering Research Laboratories to provide software for use when
creating pavement inventories, projecting future pavement condition,
and determining the future cost of pavement maintenance and
rehabilitation. 

\2 The majority of airports submitting hard copy data used a form of
MicroPAVER as their pavement management software.  However, one
company, LAW Engineering and Environmental Services, Inc., provided
us with hard copy data so that we could enter the data into
MicroPAVER 4.0.  LAW maintains data for its clients in its own
pavement management software. 

\3 Advisory Circular 150/5380-6 Guidelines and Procedures for
Maintenance of Airport Pavements (Dec.  3, 1982). 


   DETERMINING CURRENT AND FUTURE
   CONDITION OF RUNWAY PAVEMENTS
   WITH PCI DATA
--------------------------------------------------------- Appendix I:2

To ascertain the condition of the runways within the MicroPAVER 4.0
database, we determined the rate at which runway pavement
deteriorated over time and applied the deterioration curves to the
sections in our database.  To accomplish this task, we created a
series of prediction "family" models within the MicroPAVER 4.0
software using an approach explained by pavement expert Dr.  M.Y. 
Shahin.\4 This approach includes the following steps: 

  -- Define the pavement families.  According to Dr.  Shahin, a
     pavement family is defined as "a group of pavement sections with
     similar deterioration characteristics." We created a series of
     models using combinations of the following characteristics: 

  -- Pavement type.  We analyzed four pavement types--asphalt,
     portland cement concrete, asphalt concrete overlay over portland
     cement concrete, and asphalt concrete overlay over asphalt
     concrete. 

  -- Pavement use.  Only runways were included in the analysis. 

  -- Airport size.  We analyzed pavement type by size of airport,
     using the definitions employed by FAA (general
     aviation/reliever, commercial service, large hub, medium hub,
     small hub, nonhub). 

  -- Climate.  We created a database that assigned a climate variable
     to each airport on the basis of a climate map developed by
     Professor Samuel Carpenter, University of Illinois. 

  -- Filter the data.  According to Dr.  Shahin, MicroPAVER 4.0
     "allows the user to filter out suspicious data points." We
     defined a set of broadly defined boundaries (using PCI and age
     of pavement) and excluded data points that fell outside of the
     boundaries.  Most data outside of the boundaries were considered
     errors and were eliminated from the database. 

  -- Develop PCI models based on pavement characteristics.  We used
     about 60 models in MicroPAVER 4.0 and assigned sections to
     models that best fit the characteristics of the model.  If a
     model did not clearly demonstrate pavement deterioration over
     time, we assigned the affected sections to a default
     deterioration model provided by the software. 

  -- Predict the pavement section condition.  According to Dr. 
     Shahin, "the PCI prediction at the section level uses the (rate
     of deterioration established in the ) pavement family prediction
     model.  The prediction function for a pavement family represents
     the average behavior of all sections of that family.  The
     prediction for each section is done by defining (individual
     sections') position relative to the (rate of deterioration of
     other sections with similar characteristics)."

Using modeling tools in MicroPAVER 4.0, we analyzed the 4,905 runway
sections in our database and predicted each section's PCI for the
years 1998 and 2007.  We used the section-by-section PCI information
to create weighted average PCI ratings for entire runways at airports
that had PCI data, weighing by section area.  We aggregated the
results of the condition analysis by airport type and reported the
condition information in chapter 2 of this report. 


--------------------
\4 Pavement Management for Airports, Roads, and Parking Lots (New
York, NY:  Chapman & Hall, 1994). 


   FUTURE COST OF MAINTAINING AND
   REHABILITATING RUNWAYS WITH PCI
   DATA
--------------------------------------------------------- Appendix I:3

To determine the future cost of maintaining and rehabilitating the
runways at the 1,154 airports in our database, we (1) developed
budget scenarios for the amount of money airports might have
available to spend, (2) determined the unit cost of maintenance and
rehabilitation treatments, and (3) specified the relationship between
the condition and the unit cost of maintenance and rehabilitation. 
Each of these steps is described below. 


      BUDGET SCENARIOS
------------------------------------------------------- Appendix I:3.1

We created two budget scenarios--one with an unlimited amount of
funds available (the first budget scenario) and the other imposing
more funding limitations, largely on the basis of historical AIP
allocations of runway rehabilitation and maintenance funds (the
second budget scenario). 

The second budget scenario may actually overstate the level of AIP
funding traditionally received by these airports, however, because we
applied an historical allocation of all AIP runway rehabilitation and
maintenance funds to just this 35 percent of the airports eligible to
receive such funds.  We decided on this course of action because (1)
we could not readily determine what percentage of AIP funding these
airports could expect in the future and (2) we were unable to analyze
other sources of funding that airports might use.  Because of the
approximate nature of the second budget scenario, we did not attempt
to present the dollars in any other format than their nonadjusted,
nominal state. 


      UNIT COST OF MAINTENANCE AND
      REHABILITATION
------------------------------------------------------- Appendix I:3.2

Using data provided by our advisory panel (see app.  IV), we
developed a set of unit cost data to use in determining the cost of
maintenance and rehabilitation, as detailed in tables I.1 through
I.4. 

The first category of cost is localized preventive maintenance and
repair, which is defined as distress maintenance activities performed
with the primary objective of slowing the rate of deterioration. 
These activities include crack-sealing, joint resealing, and patching
and are typically applied every few years (for our purposes, we used
only the maintenance treatments listed in table I.1).  Treatments are
applied to pavements above the critical PCI.\5



                               Table I.1
                
                 Cost Factors for Localized Preventive
                              Maintenance

Treatment                                                         Cost
----------------------------------------  ----------------------------
Crack-sealing                                        $2.00/linear foot
Joint (or crack) resealing                           $2.00/linear foot
----------------------------------------------------------------------
Source:  GAO's analysis of data provided by pavement advisors. 

The second category of costs is global preventive maintenance, which
is defined as activities applied to entire pavement sections with the
primary objective of slowing the rate of deterioration.  These
activities include surface treatments for asphalt-surfaced pavements
only.  Treatments are applied to pavements above the critical PCI. 
(See table I.2.)



                               Table I.2
                
                   Cost Factors for Global Preventive
                              Maintenance

Distress                      Treatment         Interval          Cost
----------------------------  ------------  ------------  ------------
Minimal                       Fog seal           5 years        $0.05/
                                                           square foot
Climate-related               Slurry seal        5 years        $0.25/
                                                           square foot
Skid-causing                  Thin overlay      10 years        $0.70/
                               (less than                  square foot
                               2")
----------------------------------------------------------------------
Source:  GAO's analysis of data provided by pavement advisors. 

The third category of costs is major maintenance and rehabilitation,
which is defined as activities applied to the entire pavement section
to correct or improve existing structural or functional requirements. 
Major maintenance and rehabilitation is also used to upgrade
pavements that are below the critical PCI.\6 The activities include
reconstruction and structural overlays.  (See table I.3.)



                               Table I.3
                
                 Cost Factors for Major Maintenance and
                        Rehabilitation--Asphalt

Airport type                     PCI range  Treatment             Cost
----------------------------  ------------  ------------  ------------
Large hub                             0-40  Reconstruct     $55/square
                                                                  yard
                                     50-70  Overlay         $20/square
                                                                  yard
Medium hub                            0-40  Reconstruct        $45.30/
                                                           square yard
                                     50-70  Overlay             $19.3/
                                                           square yard
Small/nonhub                          0-40  Reconstruct        $41.60/
                                                           square yard
                                     50-70  Overlay         $15/square
                                                                  yard
General aviation                      0-40  Reconstruct        $26.34/
                                                           square yard
                                     50-70  Overlay            $10.15/
                                                           square yard
----------------------------------------------------------------------
Note:  These cost figures assume only the cost of the runway project
(remove existing materials, purchase replacement materials, lay
materials). 

Source:  GAO's analysis of data provided by pavement advisors. 



                               Table I.4
                
                 Cost Factors for Major Maintenance and
                        Rehabilitation--Concrete

Airport type                  PCI Range     Treatment     Cost
----------------------------  ------------  ------------  ------------
Large hub                     0-40          Reconstruct   $71/square
                                                          yard

                              50-70         Overlay       $23.3/
                                                          square yard

Medium hub                    0-40          Reconstruct   $64.30/
                                                          square yard

                              50-70         Overlay       $20/square
                                                          yard

Small/nonhub                  0-40          Reconstruct   $61.60/
                                                          square yard

                              50-70         Overlay       $20/square
                                                          yard

General aviation              0-40          Reconstruct   $49/square
                                                          yard

                              50-70         Overlay       $12.67/
                                                          square yard
----------------------------------------------------------------------
Note:  These cost figures assume only the cost of the runway project
(remove existing materials, purchase replacement materials, lay
materials). 

Source:  GAO's analysis of data provided by pavement advisors. 


--------------------
\5 These types of maintenance are generally not eligible for AIP
funding. 

\6 Sections with a PCI higher than the stated PCI range in the
overlay category were regarded as "do nothing" for major maintenance
and rehabilitation. 


      RELATIONSHIP BETWEEN
      CONDITION AND UNIT COST
------------------------------------------------------- Appendix I:3.3

MicroPAVER 4.0's budget management program examines the condition of
a particular section and assigns the appropriate maintenance or
rehabilitation treatment (and its associated cost).  Establishing the
point at which a section would be rehabilitated versus
maintained--the critical PCI--is key to obtaining the most
cost-effective system.  The critical PCI procedure, according to FAA,
Dr.  Shahin, and others is based on the concept that it is more
economical to maintain pavements above rather than below the critical
PCI because as deteroriation increases the unit cost of repair also
increases.  After consultation with our advisory panel and other
pavement consultants and airports, we established a critical PCI for
primary airports (65) and one for nonprimary airports (55). 

In MicroPAVER 4.0's maintenance and rehabilitation program, costs
were determined in the following manner: 

  -- Sections at or below critical PCI .  The program determined the
     type of reconstruction required (depending on the PCI rating and
     the distress types/amounts associated with the section).  Then
     the program checked to determine if funds were available to
     accomplish the project.  If the project could be funded, the PCI
     was reset to 100.  If funds were not available, the program
     would check funding availability in future years. 

The program also assigned priority among various projects.  For
example, if three runways had PCI's of 60, 55, and 40 respectively
(and all other variables were equal), the program assigned funds
first to the runway with the PCI of 60 to maximize its limited funds. 
Runways with poor, very poor, and failed PCI ratings were assigned
the lowest priority for funding because once pavements deterioriate
to that point it would be expensive to rehabiliate them at any time. 

  -- Sections above critical PCI with no structural distress.  The
     program determined whether the section required localized
     preventive maintenance or global preventive maintenance (after
     determining that the specified interval between applications and
     the total number of applications had not been exceeded). 

  -- Sections above critical PCI with structural distress.  The
     program determined the cost of reconstruction or structural
     overlay for the section and checked to ascertain whether funds
     were available.  The project would then either receive funding
     or be postponed and revisited in future years. 

This analysis was conducted for both the first and second budget
scenarios.  The costs were analyzed by airport and pavement type and
then aggregated by airport type and reported in chapter 3. 


   PREDICTING CURRENT CONDITION OF
   RUNWAYS LOCATED AT AIRPORTS NOT
   INCLUDED IN THE MICROPAVER 4.0
   DATABASE
--------------------------------------------------------- Appendix I:4

To determine the runway conditions at airports not in the MicroPAVER
4.0 database, we conducted a regression analysis on the MicroPAVER
4.0 runways to identify a group of characteristics that tended to be
significantly associated with runway conditions.  A regression model
is a type of statistical model that investigates the relationships
among variables.  For this study, we used regression analysis to
explore which factors, called independent variables, are associated
with the pavement conditions, called the dependent variable, for
runways at airports having PCI data.  Unlike PCI data, information on
these independent variables was available for most airports.  We then
used the resulting regression equations to estimate runway pavement
conditions at the other airports. 

Using the section-by-section PCI information available in the
MicroPAVER 4.0 database, we first created PCI ratings for entire
runways.  This was necessary because the independent variables in our
model are all either runway or airport characteristics obtained from
other databases that did not have the same level of specificity as
the MicroPAVER 4.0 data.  Our measure of pavement condition at the
runway level was calculated as the weighted average of the PCI
ratings across all sections at a runway, weighted by the area of the
section.  Similarly, we calculated a runway's age as the weighted
average age across all sections at the runway, weighted by the
section area. 

In addition to runway age, we used several other runway or airport
characteristics as independent variables in our model.  These were
obtained from either FAA's Airport Safety Program Database (also
called the 5010 database), AIP project data for 1982-97, the CIP data
for 1997, operations data obtained from FAA, or our survey of the
states on airfield maintenance programs.  We did not audit the
accuracy of these databases but did perform some limited
cross-checking of information to assess their reasonableness.  In
addition, we developed a climate database derived from climate
information developed by Professor Samuel Carpenter, University of
Illinois.  He divided the continental United States into climatic
zones.  We assigned each airport a climatic zone; however, this
confined our analysis to 3,000 airports because we disregarded
airports outside the continental United States.  The climate data
were traced to the source.  Together with the runway-level MicroPAVER
4.0 data, we used these sources to create a data set that included
the characteristics of runways and their associated airports.  The
data set contained a record for each of 1,647 runways, located at
1,154 airports having PCI data. 

To examine which factors are associated with pavement condition at
these 1,647 runways, we used ordinary least-squares regression
models.  We developed several different models, looking at the
contribution each independent variable made to the predictive ability
of the model, and the overall explanatory power of the model as
measured by the R-squared.  R-squared is a measure of the proportion
of the total variation in the dependent variable that can be
explained by the independent variables in that particular model. 

We modeled asphalt, cement concrete, and mixed-surface runways
separately.  For this analysis, asphalt included the surface types of
asphalt; asphalt concrete overlay over portland cement concrete; and
asphalt concrete overlay over asphalt concrete; cement concrete
runways were those made entirely of portland cement concrete; and
mixed-surface runways were those with a combination of at least one
of the asphalt types and cement concrete.  However, because the
asphalt model and the cement concrete model were similar, we combined
that data, resulting in just two groups of runways being modeled
separately.  Our data included 1,576 runways that were either asphalt
or cement concrete and 71 runways that were of mixed-surface type. 

The dependent variable in all models was the weighted average runway
PCI rating.  The independent variables included in the final model
for the 1,576 asphalt or cement concrete runways are the following: 

  -- the weighted average age for the runway;

  -- an indicator variable whose value was 1 if the runway was
     constructed of cement concrete and whose value was 0 if the
     runway was constructed of asphalt;

  -- a set of eight indicator variables to categorize runways as
     being located in one of nine climate zones (wet/freeze,
     wet/freeze-thaw, wet/no freeze, intermediate/freeze,
     intermediate/freeze-thaw, intermediate/no freeze, dry/freeze,
     dry/freeze-thaw, and dry/no freeze);

  -- a set of two indicator variables to categorize runways as being
     located at one of three airport types (general aviation,
     reliever, or other airports);

  -- an indicator variable whose value was 1 if the airport received
     some AIP funding for runway construction or improvement since
     1982 at any of its runways, and whose value was 0 otherwise;

  -- an indicator variable whose value was 1 if the airport indicated
     any planned future spending for runway construction or
     improvements at any of its runways (in the CIP database), and
     whose value was 0 otherwise;

  -- the amount of planned future spending at the airport for runway
     construction or improvements at any of its runways (in the CIP
     database);

  -- the number of operations at the airport, using actual amounts
     from air traffic control towers when available and otherwise
     using operation estimates from FAA's 5010 database; and

  -- an indicator variable whose value was 1 if the airport was
     located in a state with an airfield maintenance program and
     whose value was 0 otherwise. 

This model appeared to fit the data as well as any of the other
models we fit, as measured by the R-squared value.  Diagnostic tests
revealed no evidence that the inherent assumptions in the regression
model were violated, so this became our final regression model for
the asphalt and cement concrete runways.  The R-squared value is .28
for this model.  Table I.5 shows the statistically significant
effects. 



                               Table I.5
                
                  Airport and Pavement Characteristics
                   Identified as Predictive of Runway
                  Conditions at Airports With PCI Data

                                          Nature of relationship with
Characteristic                            pavement condition
----------------------------------------  ----------------------------
Age of pavement                           With all other factors being
                                          equal, for an increase in
                                          age there is a corresponding
                                          decrease in pavement
                                          condition

Type of pavement                          With all other factors being
                                          equal, concrete pavements
                                          have better pavement
                                          conditions, on average, than
                                          asphalt pavements

Type of airport                           With all other factors being
                                          equal, general aviation
                                          airports tend to have worse
                                          pavement condition than
                                          other airports

Climate                                   With all other factors being
                                          equal, there are significant
                                          differences among the
                                          average pavement conditions
                                          found in different climates

AIP funding for runway improvement        With all other factors being
projects                                  equal, airports that tend to
                                          receive AIP funds have
                                          better pavement conditions,
                                          on average, than those
                                          airports that do not tend to
                                          receive AIP funds

Airport plans for future runway           With all other factors being
improvement or construction projects      equal, airports that plan to
                                          spend capital in the future
                                          have worse pavement
                                          conditions, on average, than
                                          those airports not planning
                                          to spend funds on runway
                                          projects.
----------------------------------------------------------------------
To assess the predictive power of the model, we used double
cross-validation analysis.  We randomly split the data set into two
equal size sets of 788 runways each.  We then developed regression
models for each half, using the set of independent variables
discussed above.  Using the independent variables' values from one
half of the data, we then used the estimated regression equation
coefficients developed with the other half of the data to predict PCI
ratings.  These predicted PCI ratings were compared to the actual
weighted average runway PCI ratings for that half of the data.  The
squared correlation coefficient between the predicted and actual
runway PCI ratings was calculated.  This is called the
cross-validated R-squared, and it is a measure of the predictive
ability of the model.  We repeated this analysis for both halves of
the original data set, resulting in two cross-validated R-squared
measurements.  The values were .23 and .29, both similar to the
original R-squared of the total data set (.28). 

We separately modeled the mixed-surface runways, again using the
weighted average runway PCI ratings as the dependent variable.  The
independent variables included in the final model for the 71 mixed
surface runways are the following: 

  -- the weighted average age for the runway,

  -- an indicator variable whose value was 1 if the airport was
     general aviation or reliever, and whose value was 0 otherwise,
     and

  -- an indicator variable whose value was 1 if the airport received
     some AIP funding for runway construction or improvement since
     1982 at any of its runways, and whose value was 0 otherwise. 

This model appeared to fit the data as well as any of the other
models we fit, as measured by the R-squared value.  Diagnostic tests
revealed no evidence that the inherent assumptions in the regression
model were violated, so this became our final regression model for
the mixed-surface runways.  The R-squared value is .35 for this
model.  The runway age is the only statistically significant effect. 
Because of the relatively small size of this group of runways, we
were unable to perform a cross-validation as we did with the asphalt
or cement concrete runways. 

We estimated these regression equation coefficients to predict PCI
ratings for those runways not included in the MicroPAVER 4.0 data
set.  We needed to create a data set containing one record for each
of these runways, including data for each of the independent
variables used in our models.  There were 2,177 national system
airports without detailed pavement condition data excluded from our
MicroPAVER 4.0 database.  299 of these airports were excluded because
they either were not located in the continental United States or did
not currently exist (planned or closed), leaving 1,878 airports.  An
additional 103 of these airports were not included in the FAA 5010
database and so were dropped from our analyses.  The resulting 1,775
airports, together with the 1,154 airports in our MicroPAVER 4.0
database, made up our universe for analysis of 2,929 airports, having
a total of 4,794 runways listed in FAA's 5010 database.  Of these
runways, 1,647 runways had PCI information in our MicroPAVER 4.0
database, leaving 3,147 without PCI information.  However, because
the runway identifiers in the MicroPAVER 4.0 file were unreconcilable
with those in FAA's 5010 data set, we were unable to determine
exactly which of the 4,794 runways had PCI data.  Therefore, we
matched the two files at the airport level, selecting only those
airports having no runways at all in the MicroPAVER 4.0 database. 
This method will exclude some runways because at some airports only a
subset of the runways have PCI information.  Rather than attempting
to predict PCI information for 3,147 runways, we were able to
conclusively identify 2,812 runways in FAA's data sets that were not
a part of our MicroPAVER 4.0 database.  This methodology allowed us
to identify approximately 90 percent of the runways without PCI
ratings in our universe of analysis.  Out of this set of 2,812
runways, there were 365 runways whose surface type, as contained in
FAA's 5010 database, was something other than asphalt, cement
concrete, or a mix of the two.  These surfaces were those for which a
PCI rating does not make sense--for example, turf or water surfaces,
and were therefore excluded from our analyses.  This left us with
2,447 runways for which we attempted to predict PCI ratings. 

For these runways, we created a data set containing information for
each of the independent variables.  However, there was no source of
information for runway age, which was seen to be an important
predictor of pavement condition in our regression models.  To
estimate runway age, we used dates relating to runway construction or
improvement projects contained in the AIP data set.  If a runway had
no information for such projects in the AIP database, we considered
that runway to be at least as old as our data for AIP projects.  An
FAA official told us that this was a reasonable approach, and that he
would assign an accuracy rate of approximately 90 percent to this
methodology.  To assign an estimated age to those runways with no AIP
projects, we used the age distribution of the older runways from the
MicroPAVER 4.0 data set. 

We compared the distributions of the independent variables for both
the runways without PCI data and those with PCI data contained in our
MicroPAVER 4.0 database.  The initial comparisons of these
characteristics showed that both groups were fairly similar in terms
of these distributions.  Therefore, we would expect that the pavement
conditions at the airports without PCI data would be unlikely to be
highly dissimilar to the conditions at those airports with PCI data. 

For the runways at airports without PCI data, we then evaluated the
estimated regression equations, using each runway's values for the
independent variables, to calculate an estimated PCI rating for each
runway.  We used either the asphalt/cement concrete or the
mixed-surfaces equation as appropriate for a runway's surface type. 
We had sufficient data to predict a PCI rating for 2,433 runways
located at 1,705 airports.  As we expected, the distribution of
estimated PCI scores for these runways was not highly dissimilar to
the distribution of the actual weighted average PCI scores for those
runways having information in our MicroPAVER 4.0 database. 

Although our estimated PCI ratings were not precise enough to allow
us to project future conditions and expenses, our work was sufficient
to lead us to conclude that the general nature of what we found among
airports with PCI data was not likely to be highly dissimilar to what
would be found if the rest of the national system airports had PCI
data. 


AIRPORTS GAO VISITED
========================================================== Appendix II

This appendix provides a list of the airports GAO visited during this
review.  The airports are listed by state and within the state, by
city, airport name, and location identifier. 


   ALABAMA
-------------------------------------------------------- Appendix II:1

Alabaster, Shelby County Airport (EET)
Bessemer, Bessemer Airport (EKY)
Birmingham, Birmingham International Airport (BHM)
Centreville, Bibb County Airport (0A8)
Clanton, Gragg-Wade Field (02A)
Fort Deposit, Fort Deposit-Lowndes County Airport (67A)
Montgomery, Dannelly Field (MGM)
Prattville, Autauga County Airport (1A9)
Selma, Craig Field (SEM)
Wetumpka, Wetumpka Municipal Airport (08A)


   ARKANSAS
-------------------------------------------------------- Appendix II:2

Blytheville, Blytheville Municipal Airport (HKA)
Fayetteville, Drake Field (FYV)
North Little Rock, North Little Rock Municipal Airport (1M1)
Osceola, Osceola Municipal Airport (7M4)
Rogers, Rogers Municipal-Carter Field (ROG)
Springdale, Springdale Municipal Airport (ASG)
West Memphis, West Memphis Municipal Airport (AWM)


   CALIFORNIA
-------------------------------------------------------- Appendix II:3

Auburn, Auburn Municipal Airport (AUN)
Fallbrook, Fallbrook Community Airpark (L18)
Hemet, Hemet-Ryan Airport (HMT)
Palm Springs, Thermal Airport (TRM)
Riverside, Riverside Municipal Airport (RAL)
Sacramento, Sacramento International Airport (SMF)
San Diego, Brown Field Municipal Airport (SDM)
San Bernadino, San Bernadino International Airport (SBD)
South Lake Tahoe, Lake Tahoe Airport (TVL)
Truckee, Truckee-Tahoe Airport (TRK)


   FLORIDA
-------------------------------------------------------- Appendix II:4

Bartow, Bartow Municipal Airport (BOW)
Clearwater, Clearwater Air Park (CLW)
St.  Petersburg/Clearwater, St.  Petersburg/Clearwater International
Airport (PIE)
Orlando, Kissimmee Municipal Airport (ISM)
Orlando, Executive Airport (ORL)
Plant City, Plant City Municipal Airport (PCM)
St.  Petersburg, Albert Whitted Airport (SPG)
Winter Haven, Winter Haven's Gilbert Airport (GIF)
Zephyrhills, Zephyrhills Municipal Airport (ZPH)


   MAINE
-------------------------------------------------------- Appendix II:5

Auburn, Auburn/Lewiston Municipal Airport (LEW)
Bethel, Colonel Dyke Field (0B1)
Oxford, Oxford County Regional Airport (81B)
Pittsfield, Pittsfield Municipal Airport (2B7)
Portland, Portland International Jetport (PWM)
Waterville, Waterville Robert LaFluer Airport (WVL)


   MINNESOTA
-------------------------------------------------------- Appendix II:6

Aitkin, Aitkin Municipal Airport (AIT)
Brainerd, Brainerd-Crow Wing County Regional Airport (BRD)
Cambridge, Cambridge Municipal Airport (CBG)
Detroit Lakes, Detroit Lakes Airport (DTL)
Hawley, Hawley Municipal Airport (04Y)
South St.  Paul, South St.  Paul Municipal-Richard E.  Fleming Field
(D97)
St.  Cloud, St.  Cloud Regional Airport (STC)


   NEW HAMPSHIRE
-------------------------------------------------------- Appendix II:7

Concord, Concord Municipal Airport (CON)
Laconia, Laconia Municipal Airport (LCI)
Lebanon, Lebanon Municipal Airport (LEB)
Newport, Parlin Field (2B3)
Portsmouth, Pease International Tradeport (PSM)
Whitefield, Mt.  Washington Regional Airport (HIE)


   NORTH DAKOTA
-------------------------------------------------------- Appendix II:8

Bottineau, Bottineau Municipal Airport (D09)
Casselton, Casselton Regional Airport (5N8)
Cooperstown, Cooperstown Airport (S32)
Dickinson, Dickinson Municipal Airport (DIK)
Harvey, Harvey Municipal Airport (ND17)
Hettinger, Hettinger Municipal Airport (HEI)
Jamestown, Jamestown Municipal Airport (JMS)
Mohall, Mohall Municipal Airport (HBC)


   TENNESSEE
-------------------------------------------------------- Appendix II:9

Dyersburg, Dyersburg Municipal Airport (DYR)
Jackson, McKellar-Sipes Regional Airport (MKL)
Knoxville, Knoxville Downtown Island Airport (DKX)
Lexington, Franklin Wilkins Airport (M52)
Morristown, Moore-Murrell Airport (MOR)
Columbia/Mt.  Pleasant, Maury County Airport (MRC)
Murfreesboro, Murfreesboro Municipal Airport (MBT)
Parsons, Scott Field (0M1)
Rockwood, Rockwood Municipal Airport (RKW)
Smyrna, Smyrna Airport (MQY)
Trenton, Gibson County Airport (TGC)


   VERMONT
------------------------------------------------------- Appendix II:10

Lyndonville, Caledonia County Airport (6B8)
Middlebury, Middlebury State Airport (6B0)
Barre/Montpelier, Edward F.  Knapp State Airport (MPV)
Rutland, Rutland State Airport (RUT)
Burlington, Burlington International Airport (BTV)
Springfield, Hartness State Airport (VSF)




(See figure in printed edition.)Appendix III
SURVEY OF STATE AIRFIELD
MAINTENANCE PROGRAMS
========================================================== Appendix II



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)



(See figure in printed edition.)


STATES WITH AIRFIELD MAINTENANCE
PROGRAMS, AS OF SEPTEMBER 1997
========================================================== Appendix IV



   (See figure in printed
   edition.)


PAVEMENT ADVISORY PANEL MEMBERS
=========================================================== Appendix V

Robert Boyer, P.E.
District Engineer
Asphalt Institute

Margaret R.  Broten, P.E.
Project Manager/Principal
Applied Pavement Technology, Inc. 

Adil Godiwalla, P.E.
Chief, Airport Pavements
City of Houston
Department of Aviation

Stanley Herrin, P.E.
Manager, Airports
Crawford, Murphy & Tilly, Inc. 

Jo Lary
President
Pavement Consultants, Inc. 

Steven McNeeley
Chief Airport Engineer
Senior Airport Services Division
Virginia Department of Aviation

John E.  Naughton III, P.E.
Director, Airports and Training
American Concrete Pavement Associations

Ed Oshinski, P.E.
Airport Engineer
Aviation Division
Texas Department of Transportation

George Schwandt, P.E.  (Retired)
Chief Airport Engineer
City of Chicago, Department of Aviation

Mohamed Shahin
Principal Investigator
U.S.  Army Construction Engineering Research Laboratories


MAJOR CONTRIBUTORS TO THIS REPORT
========================================================== Appendix VI

Robert Aiken
Sarah Brandt
Dana Greenberg
Barbara Johnson
Julia Rachiele
Sara Ann Moessbauer
Luann Moy
Stanley Stenerson
Mindi Weisenbloom
Pamela Williams
Randy Williamson


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