From Research to Reality

Assessing

the Results

of the

Strategic

Highway

Research

Program

Assessing

the Results

of the

Strategic

Highway

Research

Program

i

Assessing the Results 

of the Strategic Highway

Research Program

Contents

Preface ii

The Strategic 

Highway Research Program 1

Moving SHRP Products 

from the Laboratory to the Field 2

SHRP Assessment Project 4

The Superpave System 5

Concrete and Structures 8

Highway Operations 11

(Maintenance and Work Zone Safety) 

LTPP: Study Continues, 

Products Roll Out 17

From Research to Reality 19

For More Information 20

Bibliography 21

Order Form 22

Further information on the SHRP assessment project is available on the Web

(www.ota.fhwa.dot.gov/roadsvr).
ii

Assessing the Results 

of the Strategic Highway

Research Program

Preface

In 1995, shortly after the 5-year Strategic Highway Research Program

(SHRP) concluded and during the early stages of the national program to encourage the implementation of SHRP products, the Transportation Research Board

(TRB) SHRP Committee suggested that a benefits-versus-costs study of SHRP be

undertaken. The committee members felt that an objective assessment of the project and the products was needed, to determine if the investment had been a wise

one. 

This report summarizes the results of that study, which was conducted

during 1996 and 1997. The overarching conclusion of the study: the economic

and safety benefits of SHRP clearly outweigh the research and implementation

costs. As a result, SHRP products have been dubbed RoadSavers, as they save

money, time, and lives on the Nation’s highways.

The study was a large task, requiring close coordination and cooperation

among a number of organizations across the country. The Federal Highway

Administration (FHWA) launched and funded the project and, assisted by the

SHRP Assessment Project Steering Group (composed of transportation consultant

Gary Byrd, Michael Cuddy of the New York State Department of Transportation,

Charlie Potts of APAC Inc., Bob Templeton of the Texas Department of

Transportation, and William Weseman of FHWA), provided overall direction for

the project. The transportation technology transfer center at the University of

Nevada-Reno (UNR) managed the project. The transportation technology transfer

centers in Florida, Indiana, Minnesota, Pennsylvania, and Texas assisted UNR in

compiling information on how State and local highway agencies were using SHRP

products. This information served as grist for the more than 100 case studies published to date of how SHRP products are being used to build, maintain, and operate safer, smoother roads. State and local agencies provided invaluable assistance

by supplying information for the case studies and then reviewing them for 

accuracy. 

The information collected by the technology transfer centers was turned

over to a team of economists and engineers at the Texas Transportation Institute.

This team conducted the economic analysis that formed the basis for the benefitsversus-costs report. 

From all of this information, Harrington-Hughes & Associates, Inc., prepared the RoadSavers case studies, brochures, videotape, and other publications

summarizing the study results.
The Strategic 

Highway Research Program

In 1987, in response to a growing national concern over the condition of

the highway system, the U.S. Congress established a 5-year, large-scale, applied

research program aimed at improving the performance, durability, safety, and efficiency of the Nation’s highway system.

Called the Strategic Highway Research Program (SHRP), it operated as a

unit of the National Research Council and under the direction of an executive

committee consisting of top-level managers from State highway agencies, industry,

and academia. Program funding came from the States, who agreed to contribute

one-quarter of 1 percent of their federal-aid highway funds for SHRP.

The SHRP staff included dozens of highway professionals “loaned” to the

program from highway agencies in the United States, as well as 12 other countries. 

The research was conducted by private organizations and universities who

competed for contracts in a formal bidding process. The research projects were

concentrated in four areas:

❑ Asphalt,

❑ Concrete and structures,

❑ Highway operations (maintenance and work zone safety), and

❑ Pavement performance (the long-term pavement performance study).

The research phase ended in 1992, and SHRP closed its doors in 1993. The

Federal Highway Administration (FHWA) then took on the task of coordinating

the national program to get the SHRP products into the hands of the users. 

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Assessing the Results 

of the Strategic Highway

Research Program
Moving SHRP Products 

from the Laboratory to the Field

The intense, concentrated research phase proved to be only the first

step in meeting the goal of building and maintaining more durable roads. Just as

important was the far-reaching implementation effort spearheaded by FHWA,

which involved making some necessary refinements to the SHRP products and

getting the products out to State and local highway agencies, so that they could

try them out for themselves. Meeting this challenge involved close partnerships

with States, industry, academia, and others.

The SHRP technology transfer effort was funded by the 1991 Intermodal

Surface Transportation Efficiency Act. An array of technical working groups

(TWGs) and expert task groups (ETGs), composed of representatives from highway

agencies, industry, academia, and FHWA, provided specialized guidance on the

products.

The American Association of State Highway and Transportation Officials

(AASHTO) and the Transportation Research Board (TRB) also placed their resources

solidly behind the SHRP implementation effort. AASHTO formed a Task Force on

SHRP Implementation to act as a catalyst for implementation. TRB established the

TRB-SHRP Committee to monitor the progress of implementation and provide

guidance and recommendations.

One of the primary vehicles for introducing highway agencies to the new

SHRP technologies has been a series of showcase workshops. These regional

workshops focus on a group of SHRP products in a particular area, such as concrete durability or pavement maintenance. Each workshop features both classroom instruction and hands-on training, as well as discussion on how the particular technologies might best be implemented in that particular region. Workshop

participants can also request to borrow the SHRP equipment, so that they can

“test drive” the new technologies on their own, before committing to purchase.

To bring engineers and technicians up to speed on the new Superpave system, FHWA has established the National Asphalt Training Center, located at the

Asphalt Institute in Lexington, Kentucky. The Center holds training courses and

provides technical assistance. FHWA’s National Highway Institute also sponsors

courses on the Superpave system. 

While showcase workshops and training courses have been prime implementation tools, FHWA has also relied on mobile laboratories to take the technology to the users. The laboratories contain state-of-the-art equipment and are

staffed by experienced instructors and technicians. The laboratories are also used

to conduct field evaluations on new equipment.

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Assessing the Results 

of the Strategic Highway

Research Program
State departments of transportation have teamed up with universities to

open regional Superpave centers. Five centers, located in Pennsylvania, Alabama,

Indiana, Texas, and Nevada, offer training to engineers, technicians, and other

highway workers and provide other services, such as ruggedness, precision, and

bias testing of the new procedures and equipment.

Although SHRP was driven by the needs of State highway agencies, local

governments have not been forgotten in the SHRP implementation program. A 3-

year project sponsored by FHWA’s Local Technical Assistance Program (LTAP)

introduced local governments to a range of SHRP products particularly suited to

their needs, such as winter maintenance strategies and pavement maintenance

guidelines. Local governments also learned about SHRP technologies through the

57 transportation technology transfer (T2) centers located across the country.

These centers, which were established under FHWA in 1982, were each sent samples of SHRP products to use in demonstration and training sessions. Local governments were encouraged to borrow the equipment for field tests.

As more and more SHRP products are tested and adopted by highway

agencies, the implementation program continues to acquire new dimensions. For

example, through the Lead States program sponsored by AASHTO, States that

have moved out ahead of the pack in implementing SHRP products are providing

technical support and guidance to their peers in other States. New showcase workshops are also being devised that will draw on users’ experiences with SHRP products to expand the depth of instruction.

These new ventures will continue to build on the vital partnerships fostered by SHRP. They will also continue to broaden the potential of the SHRP

devices, tests, and specifications, putting them in the hands of even more users. As

these products become part of everyday use, State and local governments will

move closer to the ultimate goal of a stronger, safer, and more efficient transportation system.

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Assessing the Results 

of the Strategic Highway

Research Program
SHRPAssessment Project

The SHRP assessment project was a broad, collaborative effort to determine whether the benefits to be gained from the SHRP products exceeded the

SHRP research and implementation costs. The assessment project was suggested by

the TRB-SHRP Committee. Project funding came from FHWA. The transportation

technology transfer center at the University of Nevada-Reno (UNR) was selected to

coordinate and manage the project, under a contract with FHWA. 

With the help of the transportation technology transfer centers in Florida,

Indiana, Minnesota, Pennsylvania, and Texas, UNR began collecting information

on the use of SHRP products by State and local highway agencies across the

United States. Through phone and mail surveys, the centers compiled information

for more than 100 detailed case studies. Dubbed RoadSavers, these reports describe

how highway agencies are using SHRP technologies to save money, time, and

lives.

Once the initial batch of case studies was compiled, the Texas

Transportation Institute (TTI) was contracted to conduct the second half of the

project—a macroeconomic analysis of the benefits and costs of SHRP products. A

team of economists and engineers at TTI reviewed the information collected by

the technology transfer centers and then used their knowledge and expertise to

develop a series of reports focusing on five SHRP technology areas:

❑ Superpave system.

❑ Snow and ice control.

❑ Pavement maintenance.

❑ Concrete and structures.

❑ Work zone safety.

The team evaluated the total nationwide costs of researching, developing,

and implementing the SHRP technologies. Realizing that highway agencies are not

likely to adopt the products immediately, three timelines, each reflecting a different pace of implementation, were used to estimate the costs and benefits over a

20-year period.

In calculating the financial benefits, the team looked at savings to highway agencies, which result from more durable roads and bridges and more efficient use of staff and materials. Equally important, however, in the total equation

were savings to motorists, which result from fewer crashes and delays and lower

vehicle operation and repair bills.

The results provided clear evidence that the SHRP technologies not only

make roads safer, but also cut costs. For example, TTI predicted that highway

agencies can save at least $126 million a year by implementing SHRP’s pavement

maintenance strategies. The analysis of the pace of implementation also clearly

shows that the faster these innovations are implemented, the bigger the return on

investment. For example, if States adopt just 6 of the 44 concrete test technologies

developed or evaluated under SHRP, their annual savings could range from $4.1

million at a slow pace of implementation to $15.5 million at a fast pace of implementation over the next 20 years.

Implementing SHRP products is proving to be good news for States’ roads

and their budgets. And with full implementation of most SHRP products still to

come, the $150 million invested in SHRP by Congress in 1987 will continue to

pay dividends far into the future.

The following sections summarize the key findings of the SHRP assessment project. For more information, see the resources listed on page 20.

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Assessing the Results 

of the Strategic Highway

Research Program
The Superpave System

Asphalt concrete is a major component of the highway system in the

United States, covering more than 90 percent of the Nation’s paved roads. Every

year, State and local highway agencies spend $10 billion on asphalt pavements,

and private sector expenditures total an additional $5 billion. Steadily increasing

traffic volumes and loads are taking their toll on these roads, forcing highway

agencies to commit extensive resources to rehabilitation projects. As a result,

motorists frequently encounter work zones that disrupt traffic, as well as rough

pavements that pose safety risks and damage tires and suspensions. 

SHRP’s solution was to develop a completely new approach to asphalt mix

design—the Superpave system. The Superpave system provides designers with the

tools to custom-design an asphalt pavement for the specific weather and traffic

conditions at a particular job site, instead of simply replicating a mix that has

served reasonably well in the past. 

The Superpave system has three components: 

❑ An asphalt binder specification.

❑ A design and analysis system based on the volumetric properties of 

the asphalt mix.

❑ Mix analysis tests and performance prediction models. 

Materials engineers use these components to select materials and a mix

design best able to resist two key types of pavement distress: permanent deformation and low-temperature cracking. Permanent deformation can result when a

pavement is exposed to heavy traffic and hot weather and lacks the strength to

withstand rutting. Low-temperature cracking occurs when the pavement shrinks

in cold weather. 

The Superpave system requires a new array of equipment for testing and

evaluating asphalt binders and mixes. By mid-1997, all State highway agencies

had five of the six pieces of equipment needed to test binders. The sixth binder

test device is in the final stages of development. All States also have at least one

Superpave gyratory compactor, the device used in the volumetric mix design procedures to simulate the effects of construction and traffic on an asphalt mix. 

Case Studies

Highway agencies that have built Superpave pavements report that the new system is producing more durable pavements. On highways across the country,

Superpave pavements are holding up well to heavy traffic and extremes of climate. 

In 1995, for example, the Alabama Department of Transportation (DOT)

resurfaced 8 km (5 mi) of badly rutted Route 165 with a Superpave mix. Despite

heavy truck traffic and extremely hot weather, the pavement showed virtually no

signs of rutting 2 years later, and Alabama DOT expects the pavement to last

longer than it would have if it were constructed with the State’s conventional mix.

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Assessing the Results 

of the Strategic Highway

Research Program
In a similar case, Arizona DOT

used a Superpave mix to construct an

overlay on a section of Interstate 10

near Phoenix in 1995. In its first summer, the pavement withstood heavy

traffic loads and 17 consecutive days

of temperatures above 43  ̊C (110  ̊F).

The pavement’s performance to date

indicates that it will be very resistant

to permanent deformation.

Superpave pavements have

also proven durable in cold climates.

After 4 years of cold weather and

heavy traffic, early Superpave test sections constructed on Interstate 43 in

Waukesha County and on Interstate

94 in Monroe County, Wisconsin, are

holding up better than adjacent sections constructed using Wisconsin’s conventional mix. Cold weather is also no problem for an overlay built using a Superpave

mix on a rural road in Blue Earth County, Minnesota, in August 1995: The overlay

is suffering less low-temperature cracking than a nearby, same-age overlay built

using Minnesota’s conventional mix.

After building several pavements using binders that meet the Superpave

specification, Texas DOT predicts that the specification will have tremendous benefits. Darren Hazlett of Texas DOT says, “Using the conservative assumptions that

25 percent of the asphalt Texas now uses doesn’t meet the specification and that

pavement life will gain about 2 years where we use binders that meet the

Superpave specification, I came up with an extremely rough estimate of $2.2 billion in savings over 30 years.” 

The Benefits

The economic assessment of the Superpave system focused exclusively on the role

that the asphalt binder plays in mix performance. Based on States’ experiences to

date, TTI estimated that one-fourth of the asphalt paving projects in the United

States use binders that do not meet the Superpave specification for the particular

site. Because the properties of the binder have a significant effect on the performance of an asphalt mix, the analysis found that switching to the Superpave

binder specification could increase the service life of an asphalt overlay by 25 percent (to 10 years from 8 years). Adopting the Superpave binder specification would

thus increase the service life of one in four overlays by 25 percent. 

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Assessing the Results 

of the Strategic Highway

Research Program

A Superpave overlay

under construction on

Interstate 10 in Arizona.

The overlay is performing

well despite heavy 

traffic loads and high air

temperatures in excess of

43  ̊C (110  ̊F).
The analysis also considered the following factors: 

❑ Traffic loads and volumes are expected to increase by 2.1 

percent annually.

❑ Based on early projects, Superpave binders are, on average, more expensive than other grades of binders, increasing the cost of overlays by

about 7 percent.

❑ As States implement the Superpave system, they will have higher costs

for purchasing and maintaining equipment and for employee training. 

These costs were subtracted from the projected benefits.

The assumptions about the effect of the Superpave binder specification

are fairly conservative. Even so, those assumptions yield tremendous potential savings over a 20-year period. For example, if all highway agencies adopt the

Superpave binder specification (which is only one component of the Superpave

system) within 5 years, the increase in pavement service life could save highway

agencies nationwide $637 million per year. If it takes highway agencies 10 years to

implement the specification, the annual savings could still reach $484 million.

The potential savings to motorists are more impressive. Because longerlasting overlays will mean improved pavement conditions, and thus fewer maintenance-related delays and less wear-and-tear on vehicles, motorists could save as

much as $1.7 billion per year over a 20-year period if highway agencies were to

adopt the Superpave binder specification within 5 years. If it takes 10 years to

adopt the technology, the savings to motorists could reach $1.3 billion per year.

Superpave research was the single biggest item in the SHRP budget, costing $53 million. The research, development, and implementation costs for the

Superpave binder specification are estimated at $230 million over 20 years. This

cost pales in comparison to the expected benefits, however; if it takes highway

agencies 10 years to fully implement the Superpave binder specification, they will

save more than twice the total cost of implementation every year for the next 20

years. The annual savings to motorists are more than five times as much as the

total cost of implementing the Superpave binder specification. 

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Assessing the Results 

of the Strategic Highway

Research Program
Concrete and Structures

Portland cement concrete has served as a key construction material for

more than 2,000 years. Today, it is used in virtually all bridge decks and piers in

the United States. Concrete is also used to pave many high-volume roads and for

most curbs, sidewalks, and median dividers. In all, highway agencies spend $6.5

billion a year on portland cement concrete bridges, pavements, and structures. 

Many of the concrete bridges and pavements constructed between the

1950s and the mid 1970s are showing signs of severe damage from traffic, weather, and other factors. By the late 1980s, highway agencies faced $20 billion worth

of needed repairs on steel-reinforced concrete bridges alone.

SHRP investigated ways to address and prevent the problem of deteriorating concrete bridges and pavements. Researchers developed or evaluated 44 products for concrete and structures, including:

❑ Nondestructive tools and procedures for assessing the condition of concrete structures and pavements. 

❑ New strategies for protecting and rehabilitating concrete pavements and

structures, including the use of cathodic protection and electrochemical

chloride extraction on steel-reinforced concrete bridges. 

❑ Guidelines for designing concrete mixes to make them less susceptible

to spalling, cracking, and other common problems.

❑ Ways to detect, mitigate, and prevent alkali-silica reactivity (ASR), a

chemical reaction that can cause severe damage to concrete. 

❑ Guidelines for using high-performance concrete in bridges and pavements.

Case Studies

The Kentucky Transportation Cabinet, for example, has been evaluating the

hydraulic fracture test chamber developed under SHRP. The device simulates the

effect of freeze-thaw cycles on aggregates, allowing highway agencies to screen out

aggregates susceptible to D-cracking. Where the conventional test method takes

weeks, the new method requires only days, saving money on labor and helping

the State to quickly assess the quality of aggregate.

In another case, the Nevada DOT evaluated the surface air-flow permeability meter, a new tool for assessing the permeability of concrete over reinforcing

steel. The highway agency found the device to be quick, easy to use, and dependable. 

The case studies also describe State highway agencies’ successes with SHRP

products not considered in the TTI analysis. For example, Alaska DOT bridge

inspectors have adopted a test developed by SHRP to measure the chloride content

of steel-reinforced concrete bridges. Because the test can be conducted in the field,

rather than in the laboratory, it requires less time and labor than the previous

method. Alaska DOT says the $2,000 chloride content test kit saves the agency

about $1,400 per bridge, which meant a savings of $95,000 in just 1.5 years.

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Assessing the Results 

of the Strategic Highway

Research Program
In Virginia, electrochemical chloride extraction technology, another product evaluated by SHRP, has added 12 to 15 years to the service life of two concrete

bridges. As a result, the State has avoided the traffic delays and huge costs associated with replacing a bridge. 

In Idaho, the

Transportation Department

is using SHRP’s chemical

test to detect ASR in portland cement concrete pavements and structures.

Previously, the State took

concrete samples to a private laboratory for analysis,

which cost $300 to $400

per sample and could take a

month or more. By switching to the SHRP test, says Al

Stanley of the Idaho

Transportation Department,

“We spend perhaps $40 to

$50 per sample, and we

know the results within

hours.”

The Benefits

The cost-benefit analysis covered only 6 of the 44 test methods and guidelines

developed under SHRP for concrete and structures (see sidebar, page 10). Yet highway agencies can reap substantial savings by adopting just those six test methods

and guidelines, which allow highway agencies to: 

❑ Design concrete mixes that will be more resistant to freeze-thaw cracking (D-cracking).

❑ Quickly assess the condition of existing concrete structures. 

❑ Mitigate the effects of ASR and D-cracking in structures and pavements. 

Using the six test methods and guidelines, State highway agencies can

extend the service life of bridges and cut bridge monitoring and maintenance

costs. The extent of a highway agency’s savings will depend on how quickly it

adopts these guidelines and test methods. The economic analysis found that even

if the six products were adopted by only one-fourth of all highway agencies over a

20-year period, the savings could total $4 million per year. And if all highway

agencies began using the new tests and guidelines, the savings could reach $15

million per year over a 20-year period. 

Researchers also took a look at the SHRP guidelines for mitigating damage

from ASR and D-cracking in concrete pavements. These conditions affect about 10

percent of the Nation’s 208,000 km (129,000 mi) of concrete pavements. On average, those pavements require extensive rehabilitation after 10 years of service.

The analysis assumed that the SHRP guidelines could extend the service

life of affected pavements by 70 percent (to 17 years from 10 years), thus delaying

the need for expensive rehabilitation work. If only one-quarter of highway agencies were to implement these strategies in 20 years, the savings could average $13

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Assessing the Results 

of the Strategic Highway

Research Program

Electrochemical

chloride extraction

technology has added

12 to 15 years to the

service life of this

bridge near

Charlottesville,

Virginia.
million a year. If all agencies were to adopt these tools over that period, the savings could reach $48 million per year. 

Longer-lasting concrete pavements will have even bigger benefits for

motorists. Because pavements will be in better condition, there will be less wearand-tear on vehicles. And motorists will encounter fewer delays caused by road

work. As a result, motorists could save between $38 million and $143 million a

year over a 20-year period, depending on how quickly highway agencies adopt

the new guidelines.

Highway agencies should see a quick return on the cost of researching,

developing, and implementing the SHRP tools and guidelines for concrete structures and pavements, which is estimated at $55 million over 20 years. Even if

highway agencies implement the products slowly, they could still recover that

cost in less than 4 years.

More Innovative Products Lie Ahead

Many of the products SHRP developed or evaluated for concrete structures are relatively complex and expensive and are therefore difficult to implement. Several

ongoing initiatives are helping State highway agencies to overcome the implementation hurdles.

One such product is high-performance

concrete, which can be used to build bridges and

pavements that are more durable and cost-effective than bridges built with conventional concrete mixes. FHWA is helping to fund construction of bridge and pavement projects that

demonstrate the capabilities of high-performance

concrete.

In another example, FHWA is facilitating

loans of a van-mounted ground-penetrating radar

(GPR) system. The GPR technology is a nondestructive way to collect information on pavements and concrete bridge decks at highway

speeds. But the equipment’s high cost can be a

barrier to implementation. The equipment loan

program allows highway agencies to decide if the

technology is worth the cost—before committing

any funds.

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Assessing the Results 

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TTI’s analysis of SHRP’s concrete and structures research covered the following six products. 

❑ Hydraulic fracture test chamber, a relatively quick way to

screen aggregate supplies for materials likely to fracture

under freeze-thaw conditions. 

❑ Maturity meter, one of the field tests evaluated by SHRP for

estimating the early-age strength of newly constructed concrete structures. 

❑ Modified freeze-thaw resistance test, an alternative to current tests of a concrete sample’s susceptibility to freeze-thaw

damage that better reflects real-world conditions.

❑ Surface air-flow permeability meter, a quick method for

determining the permeability of the top 13 mm (0.5 in) of a

concrete pavement or structure. The device helps highway

agencies plan bridge and pavement maintenance projects. 

❑ Guidelines for mitigating damage caused by ASR in existing

concrete pavements and structures.

❑ Guidelines for mitigating cracks in concrete pavements and

bridges that are caused by freeze-thaw cycles. 
Highway Operations 

(Maintenance and Work Zone Safety)

Nearly one-third of the $90 billion spent every year on the Nation’s

highway system goes to the critical tasks of snow and ice control and pavement

maintenance and repair. Snow and ice control operations keep roads passable and

safe during winter storms. Pavement maintenance and repair operations help

pavements stay in good condition for longer periods—which means smoother

roads and less wear-and-tear on vehicles. 

The products of SHRP’s highway operations program fall into three general categories: 

❑ Pavement preservation.

❑ Work zone safety. 

❑ Snow and ice control. 

Pavement Preservation

Highway agencies in the United States spend $25 billion annually on pavement

maintenance. But soaring traffic volumes and truck loads make it more and more

difficult to keep up with maintenance needs. As a result, many highway agencies

face a backlog of maintenance tasks, which means more pavements are in need of

repair. Poor pavement conditions can impair highway safety, damage vehicle tires

and suspensions, and annoy motorists.

SHRP researchers developed and evaluated ways to make pavement maintenance and repair operations more effective and efficient. Using the SHRP guidelines on preventive maintenance strategies and pavement repair methods, highway agencies can select the optimal method for repairing potholes and cracks in

asphalt pavements and cracks and spalls in portland cement concrete pavements.

They can also select the most effective preventive maintenance treatments. The

result is a comprehensive pavement maintenance strategy tailored to the traffic,

climate, and financial realities facing a highway agency.

Case Studies 

The experiences of State and local highway agencies show that SHRP has helped

to make pavement repairs and maintenance more durable and cost-effective. For

example, Alaska DOT’s Glennallen District decided several years ago that it would

no longer use expensive, poorly performing cold mix materials for pothole repairs.

The district decided to switch to a patching material custom-made for conditions

in the area, as recommended by SHRP. The custom mix is performing extremely

well—pothole repairs now last two to four times as long as they used to. In addition, the new material can be stored for extended periods of time, allowing the

district, which is located in a remote area, to buy materials in bulk.

In Larimer County, Colorado, the Road and Bridge Department has adopted another pothole repair technique highly rated by SHRP—namely, the sprayinjection method. “There is absolutely no comparison between the spray-injection

method and conventional pothole patching methods,” says crew leader Ken

Mosness. “Not only is the machine faster and easier to use, but the finished work

is also very durable and longer lasting.”

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Assessing the Results 

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Research Program
The Benefits

The analysis focused on the economic benefits to be gained from using SHRP’s

guidelines on pothole patching techniques and preventive maintenance strategies.

The other products of SHRP’s pavement maintenance research have not yet been

used extensively enough to allow benefits-versus-cost comparisons.

Pothole Patching

Each year, State highway agencies spend $300 million to $400 million to fix potholes. Local highway agencies, which are responsible for three-fourths of the roads

in the United States, spend about twice that much annually.

In most cases, highway agencies patch potholes using locally available

cold-mix materials applied with the semi-permanent method or the throw-androll method. SHRP found that quality materials applied with either the throw-androll method or the spray-injection method can produce repairs that last as long as

those made using the more costly and time consuming semi-permanent method.

It is the quality of the materials, not the repair method used, that determines how

well the patch will hold up.

The analysis assumed that highway agencies could cut repair costs by 25

percent by switching to high-quality materials and using either the throw-and-roll

method or the spray-injection method. The result—a savings of between $24 million and $89 million per year, depending on how quickly the new methods are

applied over a 20-year period. 

Preventive

Maintenance

In analyzing the economic benefits

of preventive maintenance, the

study assumed that most pavements receive a preventive maintenance treatment after 10 years of

life, then have an overlay applied 5

years later. Following SHRP’s recommendations, highway agencies

would instead apply a preventive

maintenance treatment at 7 years

in the pavement’s life and again at

14 years; this would likely delay the

need for a costly overlay until the

pavement has been in service for 19

years—which could save highway agencies nationwide between $102 million and

$384 million annually, depending on how quickly they adopt this strategy.

Improved preventive maintenance strategies will save motorists money

also. Because roads will be in better condition, drivers won’t have to slow down

for rough pavement, and vehicles will suffer less damage. As a result, motorists

nationwide could save between $167 million and $627 million per year, depending on how quickly highway agencies implement the SHRP guidelines.

The study’s findings confirm that highway agencies will get their money’s

worth from SHRP research on pavement repairs and preventive maintenance.

Research, development, and implementation costs for the SHRP pavement maintenance products are estimated to be $45 million over 20 years. Using the SHRP

pavement maintenance products, highway agencies could easily save twice that

much every year.

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Assessing the Results 

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Preventive 

maintenance 

treatments such as

crack sealing, shown

here, can dramatically

extend the life of asphalt

and portland cement

concrete pavements.
Snow and Ice Control

State and local highway agencies spend about $2 billion a year on winter maintenance, keeping roads open and safe for travel during winter storms. Traditional

maintenance operations involve waiting for snow or sleet to begin sticking to

roads, then deploying plows and trucks loaded with salt and other chemicals to

clear the pavement. This approach is effective, but not particularly efficient,

because it allows ice to form a strong bond with the pavement. Breaking that

bond requires many hours of crew and equipment time, and lots of salt and sand

are required to clear the pavement and ensure safe travel conditions. These factors

make conventional winter maintenance methods tough on budgets and on the

environment. 

SHRP sought ways to make winter maintenance more efficient, less harmful to the environment, and less costly in

terms of equipment and crew time. For example, SHRP researchers developed snowplow

designs that made plowing more effective and

efficient, and they produced guidelines for

more effectively using snow fences to keep

roads clear of drifting snow and improve visibility. 

SHRP also evaluated two new technologies—anti-icing strategies and road weather information systems (RWIS). Anti-icing

strategies involve the application of salt and

other chemicals to the pavement before a

storm strikes. When the snow or sleet begins

to fall, the chemicals prevent ice or snow from

bonding to the pavement. The snow or ice

melts on the pavement, forming a wet or

slushy surface rather than an icy surface. To be

successful, anti-icing strategies require accurate, real-time information on pavement and

weather conditions. This information can be

easily collected with RWIS technology, making

anti-icing strategies easy to implement on a broad scale. Pavement and atmospheric sensors at each RWIS station monitor weather and road conditions. Real-time

data from these sensors are used with improved weather forecasting systems to

provide winter maintenance managers the information needed to determine

where—and when—to apply chemicals to prevent snow and ice from bonding to

the pavement. To help highway agencies adopt these technologies, SHRP developed guidelines on the purchase, installation, and use of RWIS systems and on the

implementation of anti-icing strategies. 

Case Studies

State highway agencies have reported considerable savings from the use of RWIS

networks. Data from an RWIS station enabled the North Dakota DOT to cut back

on the use of sand on a bridge on I-94 near Fargo, saving $10,000 to $15,000 in

just four storms. Data collected by an RWIS network along the 153-km (95-mi)

West Virginia Parkway led to savings of about $2,300 in labor costs and $6,500 in

materials costs per storm. 

13

Assessing the Results 

of the Strategic Highway

Research Program

RWIS stations, such as

this unit in Nevada, supply

highway agencies with

information that is

extremely useful in winter 

maintenance.
Recognizing the potential for savings, highway agencies are quickly implementing RWIS technology. By 1994, there were already more than 750 RWIS stations in service across the country. 

Highway agencies also report big savings from the use of anti-icing strategies. For example, the anti-icing strategy in Boulder, Colorado, has resulted in a 55

percent reduction in sand use. When all related expenses are considered, the antiicing strategy costs $1,600 per lane-km ($2,500 per lane-mi)—half the cost of the

conventional sanding and deicing strategy. 

Anti-icing techniques have other advantages. Because Oregon DOT’s antiicing strategy means much less sand is used, the highway agency is helping to

minimize air and water pollution. And because it keeps roads clearer and safer, the

anti-icing strategy has drawn praise from the State Police.

The Benefits

The study found that an anti-icing strategy coupled with RWIS technology can

reduce the amount of time that equipment and crews spend on the road and the

amount of salt, sand, and other materials needed. The analysis used data collected

as part of SHRP field trials between 1991 and 1993, which reported the annual

cost savings per mile of salt or sand truck route as ranging from $650 in areas with

100 hours of storms per winter to $6,850 in areas with 900 hours of storms per

winter. The analysis also assumed that these savings would be partially offset by

the cost of the equipment needed to implement an anti-icing strategy. 

Slightly more than half of the U.S. highway network is located in States

hit by at least 100 hours of winter storms each winter. If the State and local highway agencies in these States were to immediately begin adopting anti-icing strategies, they could reduce winter maintenance costs by almost $108 million per year.

If it took most highway agencies 20 years to switch to anti-icing techniques, the

study projects the total agency savings could range between $55 million and $81

million per year. These savings far exceed the cost of researching, developing, and

implementing the SHRP winter maintenance products, which are estimated at $45

million over 20 years. 

Motorists will benefit far more than highway agencies. Because anti-icing

strategies leave roads wet or slushy, instead of icy or snowpacked, the study predicts that the number of accidents can be expected to drop sharply, potentially

saving highway users between $229 million and $447 million per year.

Work Zone Safety

Highway maintenance zones can be hazardous for workers and motorists alike. In

1994, for example, 706 people died and 4,942 people were injured as a result of

accidents in highway work zones. The changing traffic patterns in work zones

often confuse motorists, which increases the risk of an accident. Unlike construction projects, where workers are protected by massive concrete barriers, crews on

maintenance projects are generally protected only by traffic cones and a flagger;

because the crew is continually moving down the road, it’s difficult to justify the

time and expense of installing more permanent protective devices. 

14

Assessing the Results 

of the Strategic Highway

Research Program
SHRP researchers used computer modeling, field tests, and other methods

to develop innovative, effective, and economical safety products that would also

be easy to install, use, and remove in temporary work zones:

❑ Flashing stop/slow paddle.

❑ Opposing traffic lane divider.

❑ Direction indicator barricade.

❑ Truck-mounted attenuator for chemical spreaders.

❑ Intrusion alarm.

❑ Portable rumble strip.

❑ All-terrain sign and stand.

❑ Queue length detector.

❑ Remotely driven shadow vehicle.

❑ Portable crash cushion trailer.

Most of these devices are now commercially available and are being used

by highway agencies across

the country. 

Case Studies 

States report that the SHRP

work zone safety devices are

making life better for workers and motorists. In

Kentucky, for example,

where highway agencies

have been using flashing

stop/slow paddles in work

zones on highways and city

streets, flaggers are pleased

with the device, says John

Hibbs of the Kentucky

Transportation Center.

“There is one general

response after flaggers have

used the flashing stop/slow paddle for a while: They do not want to give it up.”

Flaggers in Alabama, Maine, New Mexico, North Dakota, and other States had a

similar response. 

The Texas DOT is using the opposing traffic lane divider to keep drivers

informed when a one-way road has been changed to two-way operation. In addition to providing clear instructions to motorists, the new devices are much easier,

faster, and less costly to install than concrete barriers. “Our first concern must be

to provide better service to the public,” says Thomas Bohuslav of Texas DOT. “The

opposing traffic lane divider allows us to do that.” The Mississippi DOT agrees that

the opposing traffic lane divider is effective. “You have to take extraordinary measures to keep people constantly aware that it’s a two-way road, and the opposing

traffic lane divider does the job,” says Al Crawley of Mississippi DOT. 

15

Assessing the Results 

of the Strategic Highway

Research Program

Flaggers 

throughout Kentucky 

evaluated the 

flashing stop/slow paddle

and found the device to

be highly effective at

attracting drivers’

attention in work zones.
The benefits for workers and motorists will increase as State and local

highway agencies make wider use of the SHRP work zone safety devices. In

Minnesota, work crews will be safer once the DOT completes the process of moving the remotely driven vehicle to commercial production. The vehicle, which

serves as a buffer between a crew and oncoming vehicles, can be controlled from

the safety of the roadside. There is no driver in the truck, which means that no

one will be at risk if the shadow vehicle is hit by an errant vehicle—an all-toocommon occurrence (in 1991, for example, 25 Minnesota DOT highway maintenance vehicles were rear-ended.) Innovative devices such as the remotely driven

vehicle can reduce the risks created by work zones and make life a little less stressful—and lot less dangerous—for workers and motorists alike. 

The Benefits

To estimate the benefits and costs of the SHRP work zone safety devices, a panel of

safety experts at TTI studied two of the most widely used products—the flashing

stop/slow paddle and the opposing traffic lane divider. The flashing stop/slow paddle contains a flashing light that a flagger can activate when a motorist appears

not to be noticing the stop or slow sign upon approach to a work zone. The

opposing traffic lane divider is placed along the centerline of a roadway to alert

drivers of oncoming traffic; the device is particularly helpful when a one-way road

is temporarily converted to two-way operation.

For the purposes of the cost-benefit analysis, the researchers assigned each

fatality a value of $2.7 million, a generally accepted figure in calculating the monetary losses resulting from an accidental death. Using this figure, the 706 work

zone fatalities in 1994 had a financial cost of $1.9 billion to society. Each injury

resulting from a work zone accident was assigned a value of $24,800; the total cost

in 1994 was $122 million. Property-damage-only costs were estimated at $43 million.

According to the panel of safety experts, adopting just two of the SHRP

work zone safety devices—the flashing stop/slow paddle and the opposing traffic

lane divider—at work zones around the country could lead to a 5 percent reduction in accidents. Because the vast majority (86 percent) of people killed in work

zone accidents are occupants of vehicles, not work crews or pedestrians, 86 percent of the predicted savings were apportioned to drivers and passengers and 14

percent to highway agencies.

The two work zone safety devices will not be implemented overnight.

Depending on how quickly they adopt the two devices, State and local highway

agencies nationwide could save between $2.1 million and $4.1 million annually

over a 20-year period, after subtracting the costs of purchasing the devices. The

savings to motorists could range between $15 million and $30 million per year. 

Those benefits more than cover the expense to highway agencies of developing and implementing the safety devices. The estimated cost of researching,

developing, and implementing the SHRP work zone safety products will total $30

million over 20 years, or $1.5 million per year—less than half of what highway

agencies could save every year.

16

Assessing the Results 

of the Strategic Highway

Research Program
LTPP: Study Continues, 

Products Roll Out

Why do some pavements hold up better than others? To find out,

SHRP initiated the world’s largest and most comprehensive study of in-service

pavements—the long-term pavement performance (LTPP) program. The 20-year

program, which began in 1987, is monitoring more than 2,000 test sections on

asphalt and portland cement concrete pavements across the United States and

Canada. 

Although only at its midpoint, the LTPP program is already producing

products for highway agencies, industry, and researchers. These products

include:

❑ Pavement monitoring procedures.

❑ Materials testing procedures.

❑ Equipment standards and

calibration procedures.

Eventually, data from the LTPP

experiment will be used to develop

improved guidelines for building and

maintaining asphalt and concrete pavements. 

Because the LTPP program is

still active, the SHRP assessment project

did not attempt to evaluate costs versus

benefits. The RoadSavers case studies

do, however, show that State highway

agencies are already benefiting from

LTPP products. One example is the procedures for calibrating the falling

weight deflectometer (FWD), a tool for determining the structural strength of a

pavement. The calibration procedures were initially developed to ensure that FWD

data collected at different LTPP sites were consistent. The procedures have since

proven invaluable to State highway agencies that use FWDs in pavement management. “Now that there is a standard calibration method that every State highway

agency has access to, it guarantees a higher level of quality for our pavement

tests,” says Larry Scofield of Arizona DOT. The end result is more accurate information for highway agencies’ pavement management systems. 

Another example is the Georgia digital faultmeter. The device, developed

by the Georgia DOT and modified by SHRP, is used to measure faulting—the vertical displacement at joints in concrete pavements—and the drop-off between the

pavement and the shoulder. The conventional equipment required users to kneel

on the road while noting the equipment’s readings. The Georgia digital faultmeter

means users no longer have to kneel to take measurements, and the reading can

be “frozen,” so users can record it from the safety of the roadside. Colorado DOT

has been using the device since 1994 and says it is faster, safer, and easier to use

than conventional methods. 17

Assessing the Results 

of the Strategic Highway

Research Program

This site in New Mexico

is one of more than

2,000 asphalt and 

portland cement 

concrete pavements

being monitored as part

of the LTPP program.
LTPP experiments are helping to validate the Superpave asphalt mix

design system and are yielding valuable information on preventive maintenance

treatments. The LTPP program is also monitoring steel-reinforced concrete bridges

that have been equipped with cathodic protection systems, treated with corrosion

inhibitors, or rehabilitated using electrochemical chloride extraction—technologies initially evaluated under SHRP.

Ultimately, the program will supply data that can be used to develop new

guidelines for building, maintaining, and rehabilitating asphalt and concrete pavements. Equipped with these guidelines, highway agencies will be able to select the

most durable and cost-effective pavement designs and maintenance strategies. The

result will be pavements that last longer, require fewer repairs, and stretch highway dollars. For drivers, longer-lasting pavements will mean fewer traffic delays

caused by work zones and an end to rough roads that damage tires and suspensions. 

18

Assessing the Results 

of the Strategic Highway

Research Program
From Research to Reality

Ten years after SHRP was launched, the products of its research can be

seen in the Superpave pavements being constructed across the country, in the new

work zone safety devices that better protect workers and motorists, in new guidlines and test methods for portland cement concrete pavements and structures,

and in innovative, cost-effective strategies for pavement maintenance. Far from

being mere theories on paper or prototypes in a laboratory, SHRP products are

being used today to improve travel conditions and safety and to save money for

highway agencies and motorists.

The success of SHRP demonstrates the importance of concentrated and

focused research programs that never lose sight of their goals. SHRP stuck to its

original objectives of improving the performance of asphalt, increasing pavement

life, increasing the cost-effectiveness of maintenance, and improving the durability

and versatility of concrete pavements and structures. More than 100 new devices,

tests, and specifications later, these objectives still infuse the work of those implementing and further refining SHRP products.

Just as significant as the laboratory results was the full-scale implementation drive mounted by FHWA, AASHTO, TRB, and others. However promising and

exciting a product is in the laboratory, it can’t begin to fulfill its potential until it

is in the hands of the State and local highway agencies that maintain the country’s vast road network.

SHRP’s implementation effort succeeded, just as its research did, because it

was built on partnerships. From the very beginning, SHRP was guided not only by

FHWA, AASHTO, and TRB, but also by highway professionals from every region of

the country, from academia, and from industry. The products that emerged from

this research were not a surprise: rather, they were the culmination of extensive

and coordinated planning.

This joint planning smoothed the road to implementation. States knew

that the products being rolled out, whether they were improved snow fences or

pavement repair techniques, were designed to meet real, identified needs. And

because State representatives had been closely involved in all phases of SHRP, from

serving on the committee that oversaw the research to lending their technical

expertise as loaned staff members, they were ready to support implementation

efforts. From pooled-fund equipment purchases to regional Superpave centers,

States have been fully engaged in making the goals of SHRP a reality.

Partnerships and planning have put the results of SHRP research into the

hands of highway workers in every State. But the story does not end there. Just as

a business launching a new product measures its success against the start-up

expenses, FHWA analyzed the economic benefits of the SHRP products versus the

costs of the program. As outlined in this report and detailed in more extensive

documents, the results showed that SHRP was a winner in more ways than one:

not only do the new products improve road and travel conditions, but they provide States—and taxpayers—with a substantial return on investment. 

Assessing the economic benefits of the SHRP products provided an important culmination to the program’s work and an additional validation of the value

of its research. In an era of tight budgets for highway agencies and increased cost

consciousness, it is not enough to outfit agencies with promising products. As in

today’s business world, promising products that also pay smart dividends are the

ones that ultimately succeed.

19

Assessing the Results 

of the Strategic Highway

Research Program
SHRP is only one of many highway research programs in the United

States. The path blazed by SHRP and the lessons learned from SHRP will prove

helpful in planning future research programs. All parties involved have seen the

success of focused, practical research that moved steadily toward well-defined

goals; diverse partnerships in both research and implementation; and a strong

emphasis on analyzing the economic benefits attained. By building on these principles, any future research initiatives will jump-start their chances of success.

For More Information

For more information, contact:

20

Assessing the Results 

of the Strategic Highway

Research Program

The RoadSavers case studies and the reports from the University of Nevada-Reno and the

Texas Transportation Institute are available from FHWA’s Office of Technology Applications

Web site (www.ota.fhwa.dot.gov/roadsvr). 

More information on the Long Term Pavement Performance

program is available on the LTPP Web site (http://www.tfhrc.gov/pavement/ltpp/

ltpphome.html).

Focus, a monthly newsletter published by FHWA, covers how innovative products, including the products of SHRP, are being used to build better, safer roads. For more information, 

contact Harrington-Hughes & Associates, Inc. 

(telephone: 202-347-1414; 

fax: 202-347-6938; 

email: kathrynhh@harringtonhughes.com; 

Web: www.ota.fhwa.dot.gov/pubs/index.html).

Federal Highway Administration

Mike Halladay

SHRP Implementation Coordinator

Federal Highway Administration

400 Seventh St., S.W., HTA-3

Washington, DC 20590

telephone: 202-366-6503

fax: 202-366-7909

email: 

michael.halladay@fhwa.dot.gov

Texas Transportation Institute

Dallas Little

Jeffery Memmott

Charlie Wootan

Texas A&M University System

College Station, TX 77843

telephone: 409-845-1713

fax: 409-845-9356

University of Nevada-Reno

Maria Ardila-Coulson

Jon Epps

College of Engineering/257

University of Nevada

Reno, NV 89557

telephone: 702-784-1433

fax: 702-784-1429

Harrington-Hughes 

& Associates, Inc.

Kathryn Harrington-Hughes

733 15th Street, N.W., Suite 700

Washington, DC 20005

telephone: 202-347-1414

fax: 202-347-6938

email:

kathrynhh@harrington-hughes.com
Bibliography

RoadSavers (case studies). Publication No. SA-96-045. Washington, D.C., Federal Highway

Administration, U.S. Department of Transportation, 1996.

The Superpave System (brochure). Publication No. FHWA-SA-97-033. Washington, D.C.,

Federal Highway Administration, U.S. Department of Transportation, 1997.

Work Zone Safety (brochure). Publication No. FHWA-SA-97-034. Washington, D.C., Federal

Highway Administration, U.S. Department of Transportation, 1997.

Snow and Ice Control (brochure). Publication No. FHWA-SA-97-035. Washington, D.C.,

Federal Highway Administration, U.S. Department of Transportation, 1997.

Pavement Preservation (brochure). Publication No. FHWA-SA-97-036. Washington, D.C.,

Federal Highway Administration, U.S. Department of Transportation, 1997.

Concrete and Structures (brochure). Publication No. FHWA-SA-97-037. Washington, D.C.,

Federal Highway Administration, U.S. Department of Transportation, 1997.

Summary of SHRP Research and Economic Benefits of Asphalt. Publication No. FHWA-SA-98-

012. Washington, D.C., Federal Highway Administration, U.S. Department of

Transportation, 1997.

Summary of SHRP Research and Economic Benefits of Concrete and Structures. Publication No.

FHWA-SA-98-013. Washington, D.C., Federal Highway Administration, U.S. Department of

Transportation, 1997.

Summary of SHRP Research and Economic Benefits of Pavement Maintenance. Publication No.

FHWA-SA-98-014. Washington, D.C., Federal Highway Administration, U.S. Department of

Transportation, 1997.

Summary of SHRP Research and Economic Benefits of Snow and Ice Control. Publication No.

FHWA-SA-98-015. Washington, D.C., Federal Highway Administration, U.S. Department of

Transportation, 1997.

Summary of SHRP Research and Economic Benefits of Work Zone Safety. Publication No. FHWASA-98-016. Washington, D.C., Federal Highway Administration, U.S. Department of

Transportation, 1997.

Economic Benefits of SHRP Research. Publication No. FHWA-SA-98-017. Washington, D.C.,

Federal Highway Administration, U.S. Department of Transportation, 1997.

From Research to Reality: Innovative Technologies for Saving Money, Time, and Lives on Our

Nation’s Highways (videotape). Videotape No. 111. Washington, D.C., Federal Highway

Administration, U.S. Department of Transportation, 1997.

Notice—the United States Government does not endorse products or manufacturers. Trade or manufacturers’ names

appear herein solely because they are considered essential to the object of the article.

Superpave is a registered trademark of the National Academy of Sciences.

21

Assessing the Results 

of the Strategic Highway

Research Program
22

Assessing the Results 

of the Strategic Highway

Research Program

Order Form

More than 100 case studies on how SHRP products are being used 

by State and local highway agencies have already been collected.

Case studies can be ordered by topic (choose from category A) 

or by State (choose from category B).

A.) Please send me the RoadSavers case studies (Publication No. FHWA-SA-96-045) for

the topics indicated below:

B.) OR the States indicated below:

❑ Superpave System

❑ Pavement Maintenance

❑ Work Zone Safety

❑ Snow and Ice Control

❑ Concrete and Structures

❑ Alabama 

❑ Alaska 

❑ Arizona 

❑ Arkansas 

❑ California 

❑ Colorado 

❑ Connecticut 

❑ Delaware 

❑ District of Columbia 

❑ Florida 

❑ Georgia 

❑ Hawaii

❑ Idaho 

❑ Illinois

❑ Indiana

❑ Iowa

❑ Kansas

❑ Kentucky

❑ Louisiana

❑ Maine

❑ Maryland

❑ Massachusetts

❑ Michigan

❑ Minnesota

❑ Mississippi

❑ Missouri

❑ Montana

❑ Nebraska

❑ Nevada 

❑ New Hampshire

❑ New Jersey

❑ New Mexico

❑ New York

❑ North Carolina

❑ North Dakota

❑ Ohio

❑ Oklahoma

❑ Oregon

❑ Pennsylvania

❑ Puerto Rico

❑ Rhode Island

❑ South Carolina

❑ South Dakota

❑ Tennessee

❑ Texas

❑ Utah

❑ Vermont

❑ Virginia

❑ Washington

❑ West Virginia

❑ Wisconsin

❑ Wyoming

❑ Please send me the following RoadSavers brochures:

❑ The Superpave System (Publication No. FHWA-SA-97-033)

❑ Work Zone Safety (Publication No. FHWA-SA-97-034)

❑ Snow and Ice Control (Publication No. FHWA-SA-97-035)

❑ Pavement Preservation (Publication No. FHWA-SA-97-036)

❑ Concrete and Structures (Publication No. FHWA-SA-97-037)

❑ Please send me the videotape From Research to Reality: Innovative Technologies for

Saving Money, Time, and Lives on Our Nation’s Highways (Videotape No. 111)

❑ Please send me From Research to Reality: Assessing the Results of the Strategic Highway

Research Program (Publication No. FHWA-SA-98-008)

Name

Address:

City, State, Zip 

Telephone 

Fax 

Email 

Please return to Federal Highway Administration, Research and Technology Report

Center, 9701 Philadelphia Court, Unit Q, Lanham, MD 20706; fax: 301-577-1421.
Publication No. FHWA-SA-98-008