TECHBRIEF

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.fhwa.dot.gov/research

Impact of Environmental

Factors on Pavement

Performance in the Absence

of Heavy Loads

FHWA Publication No.: FHWA-HRT-16-078 

FHWA Contact: Jack Springer, HRDI-30, (202) 493-3144, 

jack.springer@dot.gov 

This document is a technical summary of the Federal 

Highway Administration Long-Term Pavement 

Performance Program report, Analysis of the Study of 

Environmental Effects in the Absence of Heavy Loads

(FHWA-HRT-16-084).

The Long-Term Pavement Performance (LTPP) Program 

monitors the performance of pavements constructed 

using different materials that are subject to varied traffic 

loads across many climates. One experiment category 

developed by the program for study is the effect the 

environment has on pavement deterioration. The data 

analysis results summarized in this TechBrief use test 

sections from an LTPP Specific Pavement Studies (SPS) 

experiment, Study of Environmental Effects in the 

Absence of Heavy Loads (SPS-8), matched with test 

sections from other LTPP experiments that have normal 

truck traffic to compare and show the proportion of total 

damage caused by environmental effects. This analysis, 

which looked at data collected over a 15-year period, also 

identified many practical design and materials effects, 

including some very informative results.

Introduction

Initiated as part of the Strategic Highway Research 

Program, the primary purpose of the SPS-8 experiment 

was to characterize the impact of environmental factors 

The Long-Term Pavement Performance 

(LTPP) Program is a large research 

project for the study of in-service 

pavements across North America. Its 

goal is to extend the life of highway 

pavements through various designs 

of new and rehabilitated pavement 

structures, using different materials and 

under different loads, environments, 

subgrade soil, and maintenance 

practices. LTPP was established under 

the Strategic Highway Research 

Program and is now managed by 

the Federal Highway Administration.
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on pavement performance. The primary 

objectives of this experiment were the 

following:

• Identify and quantify the effect of 

environmental factors and design on 

asphalt concrete (AC) pavement and 

jointed plain concrete pavement (JPCP) 

performance in the absence of heavy 

loads.

• Establish environmental effects 

and develop recommendations for 

mitigating these effects through effective designs and materials selection.

• Estimate the proportion of total 

pavement damage caused by environmental factors.

The data collected from the LTPP test locations, including the SPS-8 test sections, 

are contained in the LTPP database and 

can be accessed from LTPP InfoPaveTM.(1)

The database was established to provide 

permanent storage for different pavement 

design features, materials properties, and 

performance information for use in future 

analysis and evaluation by State transportation departments.

“Environment,” in the context of this study, 

includes climatic factors (e.g., moisture, 

rainfall, temperature, and freeze/thaw) 

and foundation/subgrade type (e.g., frostsusceptible, expansive, fine-grained, coarsegrained, and soil properties such as percent 

clay and silt). The absence of heavy loads in 

the context of this study is defined as traffic 

applied to the SPS-8 test section that is typically less than 10,000 equivalent single axle 

loads a year. By contrast, companion LTPP 

test sections, such as the Strategic Study of 

Structural Factors for Flexible Pavements 

(SPS-1), Strategic Study of Structural Factors for Rigid Pavements (SPS-2), and 

General Pavement Study (GPS) sections 

with similar design features, have 10 to 100 

times as much or more traffic as the SPS-8 

sections.

Assembly of Database and Analysis

Information assembled for this study 

included detailed design, materials, construction, and performance data for each 

SPS-8 test section. All performance data 

were compared at 15 years because most of 

the sections had exceeded that time period. 

In addition, a site-by-site analysis of the 

SPS-8 projects was conducted. 

To perform the analysis for this study, companion test sections were identified from 

among the SPS-1, SPS-2, and GPS experiments that matched the design and materials characteristics of the SPS-8 sections. 

In terms of traffic, table 1 shows a dramatic difference in the annual truck levels 

(Federal Highway Administration Class 4 to 

13) between the SPS-8, Asphalt Concrete 

Pavements on Granular Base (GPS-1), 

Jointed Plain Concrete Pavements (GPS-3), 

SPS-1, and SPS-2 sections.

These large differences in annual truck 

traffic levels between the experiment groups 

made it possible to make meaningful direct 

performance comparisons of the effect 

of traffic and environmental factors on 

pavement damage and performance.

Results From SPS-8 and 

Companion Test Sections

One outcome of the comprehensive analyses performed using data from the low-trafficked SPS-8 and companion high-trafficked 
3

LTPP Experiment Mean Annual Number of Trucks in LTPP Lane

SPS-1 and GPS-1 280,124

SPS-2 and GPS-3 693,123

SPS-8 7,586

Table 1. Mean annual truck traffic for SPS-1/GPS-1, SPS-2/GPS-3, and SPS-8 sections.

SPS-1, SPS-2, GPS-1, and GPS-3 projects was the compilation of the impact of 

various environmental and design factors 

on pavement performance. Use of these 

factors demonstrates an innovative 

approach for examining individual pavement performance measures (e.g., key 

distresses and pavement roughness) to 

gain a better understanding of how pavement damage is initiated and exacerbated.

By understanding the possible initiators 

and aggravators of individual pavement 

distresses, engineers can better select the 

appropriate design features and materials 

properties to mitigate the impact of environmental factors.

AC Pavement Results

The impacts of truck traffic, pavement 

thickness, and the environment on key 

distress types and smoothness, as well 

as recommendations to address these 

impacts, are summarized as follows:

• AC fatigue cracking: This distress 

includes all alligator and linear cracks 

that occur in the wheelpaths expressed 

as a percentage of total lane area. 

Traffic loadings characterized as average annual daily truck traffic (AADTT) 

were shown to be very significant in 

initiating fatigue cracking. The lowtraffic SPS-8 sections had very little 

fatigue cracking, but the higher-traffic 

SPS-1 and GPS-1 sections had much 

greater AC fatigue cracking. AC thickness was a significant factor in 

mitigating fatigue cracking. Fatigue 

cracking was aggravated in warmer 

climates (higher in situ AC temperatures), by higher base/subgrade 

moisture content, and by lower 

subgrade fine sand content. 

Recommendations to minimize fatigue 

cracking include using appropriate AC 

layer design thickness, particularly in 

warmer and wetter climates and with 

subgrades with low sand content (e.g., 

fine-grained soils). Field results show 

that these environmental conditions 

are much more conducive to fatigue 

cracking. However, in colder climates, 

field results show that AC thickness 

does not have such a significant effect 

on fatigue cracking.

Because traffic loadings (AADTT) 

were shown to be very significant in 

initiating fatigue cracking, improving 

future AADTT and axle load spectra 

estimates for individual project designs 
4

would result in pavement designs that 

would have lower fatigue cracking. 

• Rutting (permanent deformation): 

Similar to fatigue cracking, AADTT 

loadings were shown to be very 

significant in initiating total rutting in 

all pavement layers. The low-traffic 

SPS-8 sections had very little rutting. 

Increased AC thickness was a significant factor in mitigating total rutting. 

Rutting was aggravated in wet climates 

as the number of wet days increased. 

The moisture content in the base/

subgrade was higher in these areas.

Some recommendations to decrease 

or minimize total rutting include 

improved consideration of AC thickness, binder, and mixture selection, 

especially in warmer and wetter climates. Field results show that these 

environmental conditions are more 

conducive to total rutting.

• Transverse cracking: Lower AC in situ 

temperature (as found in colder climates), higher numbers of air freeze/

thaw cycles, and subgrade type (e.g., 

active and fine-grained soil types and 

reduced fine sand content) were shown 

to have initiated and also aggravated 

transverse cracking. Higher plasticity 

index of the soil also aggravated or 

increased transverse cracking. One 

surprising finding was that there was 

substantial transverse cracking in 

no-freeze climates. This finding 

has been observed by different 

agencies in trying to calibrate the 

AASHTOWareTM Pavement ME Design 

transfer functions.(2) Both Arizona 

and Georgia have significant levels 

of transverse cracks that cannot be 

explained by cold temperature events. 

Another surprising finding was that the 

amount of transverse cracking was far 

greater when the level of truck traffic 

was higher (e.g., SPS/GPS compared 

with SPS-8).

Some recommendations to reduce the 

amount of transverse cracking include 

performing additional research to 

explain the occurrence of transverse 

cracks in warm areas (e.g., potential 

permanent shrinkage mechanism) and 

analysis showing the unexpected relationship between truck traffic and the 

occurrence of more transverse cracking in higher-traffic AC pavements. 

• Materials durability distress: Higher 

AC temperature (i.e., warmer climates) 

was identified as the common initiator 

of the various mechanisms related to 

AC materials durability distress (i.e., 

bleeding, block cracking, potholes, and 

raveling). Aggravation variables identified include lower freeze/thaw cycles 

(as found in warmer climates) and a 

larger number of wet days.

One recommendation to minimize 

durability distress includes greater 

consideration of the individual distress 

types that make up the materials durability distress in AC materials selection, 

specifically for warm and wet climates. 

Mixture durability distress is most 

prominent in warm and wet climates.

• Smoothness (International Roughness 

Index (IRI)): Higher subgrade clay 

content and higher traffic applications 
5

Distress Type Initiators

(Mechanistic Basis)

Aggravators

(Increasing Distress)

Impact of AC Thickness 

in Mitigating Distress

Fatigue cracking. Higher AADTT.

• Warmer climates 

(which lead 

to higher AC 

temperatures).

• Higher base/

subgrade moisture 

content. 

• Lower subgrade 

fine sand content 

(e.g., fine-grained 

soils).

Thinner AC layers 

experienced 

increased fatigue 

cracking.

Rutting 

(permanent 

deformation).

Higher AADTT.

High number of wet 

days (which affects 

base/subgrade 

moisture content). 

Thinner AC layers 

exhibited increased 

rutting.

Transverse cracking.

• Lower AC in situ 

temperature.

• More air freeze/

thaw cycles.

• Subgrade type 

(fine-grained soil 

types and reduced 

fine sand content).

• Higher AADTT far 

higher transverse 

cracking.

• Higher Plasticity 

Index (PI).

• Large amount of 

transverse cracking 

in no-freeze 

climates.

Not significant.

Materials durability 

distress.

Higher AC 

temperature.

• Fewer freeze/thaw 

cycles.

• Higher number of 

wet days.

Not significant.

Smoothness (IRI).

• Higher subgrade 

clay content. 

• Higher AADTT. 

More freeze/thaw 

cycles.

Reduced AC thickness 

led to greater 

smoothness loss.

Table 2. Environmental and design factors that initiate and aggravate AC pavement distress.

both appear to be initiators of loss 

of smoothness over time. The main 

aggravator was a larger number of 

annual freeze/thaw cycles.

Recommendations to improve smoothness include addressing the subgrade 

component through improved treatments to stabilize clay-type subgrades. 

Also, the impact of traffic on smoothness loss can be addressed using 

techniques that reduce fatigue cracking, 

rutting, transverse cracking, and materials durability distress.

Thickness is a critical design feature that 

affects AC distress and IRI. AC thickness was 

found to be significant for fatigue cracking, 

rutting, and smoothness loss. For these 

distresses and IRI, increasing AC thickness 

leads to lower levels of the distress and 

improved smoothness. Table 2 summarizes 

the findings of environmental and design 

variables included in this study that initiate 
6

and aggravate AC pavement distress and 

loss of smoothness.

JPCP Results

The suggested improvements to JPCP 

design and materials selection are 

presented as follows for the key distresses 

and smoothness:

• JPCP transverse fatigue cracking: 

Traffic loadings were shown to be 

very significant in initiating transverse 

fatigue cracking in JPCP. The low-traffic 

SPS-8 sections had very little fatigue 

cracking, but the higher-traffic SPS-2 

and GPS-3 sections had much higher 

amounts at 15 years. Portland cement 

concrete (PCC) thickness was also a 

very significant factor in mitigating 

fatigue cracking. Fatigue cracking was 

aggravated in warmer climates with 

higher in situ PCC temperatures (and 

gradients), increased in drier climates 

with lower precipitation, and increased 

on coarse-grained subgrades.

Recommendations to reduce fatigue 

cracking include using appropriate 

JPCP design thickness, particularly 

in warmer and drier climates, where 

there are higher built-in negative slab 

temperature gradients, higher slab 

moisture gradients, and higher slab 

negative temperature gradients. Also, 

improving future truck volume and 

load spectra predictions for individual 

project design would result in pavement designs that would have lower 

fatigue transverse cracking. 

• Joint faulting: Traffic loadings were 

shown to be significant in initiating 

transverse joint faulting in JPCP. Joint 

faulting on the SPS-8 test sections 

was very low. Faulting was greater 

for SPS-2 and GPS-3 sections but still 

generally low because all joints were 

doweled. Longer joint spacing resulted 

in greater joint faulting. Longer joint 

spacing tends to result in wider joints. 

Wider joints lose aggregate interlock, 

allowing higher differential deflections. 

Higher subgrade clay contents resulted 

in increased joint faulting. This finding 

may be related to the amount of 

erodible fines, which may contaminate 

the unbound base courses and thus 

lead to greater erosion and pumping 

beneath the joint. Greater frost 

penetration resulted in higher faulting. 

Again, colder climates will result in 

wider joint openings and reduced 

aggregate interlock throughout the 

year. This will lead directly to greater 

erosion and greater joint faulting 

under heavy traffic loadings, even with 

doweled joints.

Recommendations to lower joint 

faulting include matching the dowel 

diameter to the slab thickness to 

control faulting. The traditional rule of 

thumb is to require a dowel diameter 

(in inches) that is equal to or larger than 

the slab thickness (in inches) divided 

by 8. A 12-inch slab would thus require 

a minimum 1.5-inch dowel diameter. 

For critical climatic areas (e.g., colder 

climates with higher clay content 

subgrades), the following actions 

should be taken:

• Use a design procedure that 

considers dowel diameter and 
7

thickness in predicting joint 

faulting.

• Reduce joint spacing to keep joints 

tighter. This result was validated 

based on the fact that most of these 

sections had very low faulting after 

15 years. 

• For very heavy traffic, use a welldesigned stabilized base course. 

It may be a good solution to minimize pumping and erosion beneath 

the JPCP.

• Joint spalling: Traffic was not a significant factor in joint spalling in most 

cases, but it did show an aggravation effect in some comparisons. 

The prime initiator is the in situ PCC 

temperature, which correlates well 

with other environmental factors such 

as freeze/thaw cycles. Many cycles of 

freezing and thawing of saturated concrete (as occurs near joints) can be 

linked mechanistically to damage at 

the joint. 

The lower the in situ PCC annual temperature, the greater the amount of joint 

spalling. Thus, cold temperatures and 

corresponding freezing and thawing 

of the PCC slab appear to correlate well 

with joint spalling. Thicker slabs also 

showed a reduced level of joint spalling. This may be explained by the fact 

that the frost line does not include the 

mid or lower portion of the slab as often 

(i.e., fewer freeze/thaw cycles lower 

into the slab).

Recommendations to reduce the 

amount of joint spalling include a more 

comprehensive evaluation of PCC mixture design to handle saturated freeze/

thaw cycles over many years. Proper 

entrained air content and curing are 

essential. Internal curing may produce a PCC that is less permeable and 

less susceptible to freeze/thaw under 

saturated conditions.

• Smoothness (IRI): Traffic loadings and 

subgrade type were the potential initiators for loss of smoothness for JPCP, 

similar to AC pavement. The main 

aggravator of smoothness loss was 

higher in situ PCC temperature (warmer 

climate). The warmer the climate is, 

the greater the smoothness loss or the 

rougher the pavement will be. This is 

perhaps due in part to increased slab 

upward curling -and increased fatigue 

cracking in warmer climate zones.

Recommendations to improve smoothness include additional study into 

the reasons why granular subgrades 

would have greater smoothness loss 

than fine-grained subgrades. Also, the 

impact of traffic on smoothness loss 

can only be addressed by following 

recommendations for a reduction in 

fatigue cracking, joint faulting, and 

joint spalling.

Similar to distresses found on AC pavements, slab thickness is a critical design 

feature that also aggravates JPCP distress. 

PCC thickness was found to be significant 

for fatigue cracking, faulting, spalling, and 

smoothness loss. For these distresses and 

IRI, increasing PCC thickness leads to lower 

levels of the distresses. However, increases 

in slab thickness also require direct 
8

consideration of increased dowel diameter 

to provide adequate steel-to-concrete bearing stress for higher traffic volumes.

Table 3 summarizes the findings of environmental and design variables included in 

this study that initiate and aggravate JPCP 

distress and loss of smoothness. The findings regarding the impact of PCC thickness 

to mitigate distress are also provided.

Pavement Damage Due to 

Environmental Factors

An estimate was made of the proportion of 

pavement damage caused by environmental factors using comparisons of pavement 

damage of low-traffic SPS-8 performance 

with higher-traffic companion SPS and GPS 

sections subjected to the same environment (climate and subgrade).

AC Pavement

The performance results demonstrated that 

environmental factors, including climate 

and subgrade, are very important aspects 

of the initiation and progression of distress 

and damage in AC pavements. The analysis 

showed that environmental factors (from 

SPS-8) accounted for 36 percent of total 

damage (from traffic and environment) for 

AC pavements. Thus, about 1/3 of all damage to typically loaded flexible pavement 

Distress Type Initiators

(Mechanistic Basis)

Aggravators

(Increasing Distress)

Impact of PCC 

Thickness in 

Mitigating Distress

Fatigue cracking. Higher AADTT.

• Lower precipitation 

(in a drier climate).

• Higher in situ PCC 

temperature (in a 

warmer climate).

• Coarser subgrades.

Significant. (Thinner 

PCC pavements 

experienced 

increased fatigue 

cracking.)

Joint faulting. Higher AADTT.

• Longer joint 

spacing.

• Higher subgrade 

clay content.

• Greater frost 

penetration (in a 

colder climate).

Magnitude of faulting 

difference was very 

small. Increased 

thickness must be 

accompanied by 

increased dowel 

diameter to prevent 

faulting.

Joint spalling.

Lower PCC 

temperature (and 

higher freeze/thaw 

cycles).

• Longer joint 

spacing.

• Higher AADTT.

Significant. (Thicker 

slabs exhibited lower 

joint spalling.)

Smoothness (IRI).

• Coarse-grained 

subgrade.

• Higher AADTT.

Higher in situ PCC 

temperature (in a 

warmer climate).

Significant. (Thicker 

PCC slabs had lower 

loss of smoothness 

over time.)

Table 3. Environmental and design factors that initiate and aggravate JPCP distress.
9

was attributable to subgrade and climate 

factors. Key climate and subgrade factors 

that initiate and aggravate AC pavement 

distress are described as follows:

• Climatic zone: AC pavements located 

in warmer no-freeze climates exhibited 

significantly greater fatigue cracking 

and materials-related distress. This 

was more pronounced for the thin 

AC sections than for the thicker AC 

sections. Therefore, warm climates 

are especially critical for AC fatigue 

cracking and materials-related distress, 

and significant efforts (including 

design and materials selection) are 

needed to reduce these distresses. 

Pavements in colder climates were 

more likely to exhibit higher levels of 

transverse cracking and smoothness 

loss, although, surprisingly, significant 

amounts of transverse cracking are 

also present in warmer climates. 

• Freeze/thaw cycles: Higher numbers 

of freeze/thaw cycles resulted in 

significantly greater smoothness 

loss over 15 years. More freeze/thaw 

cycles also led to increased transverse 

cracking. However, materials durability 

distress was much lower in areas of 

with more freeze/thaw cycles. 

• Precipitation: Both wet days per year 

and base/subgrade moisture content were significant variables. Thin 

AC sections had significantly higher 

fatigue cracking levels (27.5 percent 

higher) when subjected to high precipitation. Thick AC sections showed 

no increase in fatigue cracking when 

subjected to high precipitation. 

Total rutting was also significantly 

affected by precipitation, with more 

rutting occurring in locations with 

higher numbers of annual wet days. 

Full consideration is needed of 

unbound materials softening when 

near saturation to minimize this 

distress. Materials durability distress 

was also greater with increased 

precipitation. Therefore, in areas 

of higher precipitation, the structural design (to account for reduced 

unbound material modulus in wet seasons), subdrainage design (stabilization to remove potential problems), 

and materials selection (to account for 

low moisture susceptibility) are critical.

• Subgrade soil: Subgrade-related factors showed significant impact on 

all but two distresses examined (AC 

materials durability and rutting). 

Changing specific subgrade characteristics was found to significantly 

change AC fatigue cracking and transverse cracking as follows: 

• The higher the percent fine sand 

content (coarser grained material), 

the less AC fatigue cracking.

• The higher the percent clay 

content, the greater the AC pavement smoothness loss.

• The higher the PI, the higher the 

AC transverse cracking and fatigue 

cracking.

JPCP 

The performance results have shown that 

environmental factors, including climate 
10

and subgrade, are very important aspects 

in the initiation and progression of distress and damage in JPCP. Analysis showed 

that environmental factors accounted for 

24 percent of total damage for JPCP. 

Therefore, about 1/4 of all damage to 

normally loaded JPCP is attributable to 

subgrade and climate factors. Key climate 

and subgrade factors that initiate and aggravate JPCP distress are described as follows:

• Climatic zone: JPCP located in 

warmer no-freeze climates exhibited 

significantly greater fatigue transverse 

cracking and smoothness loss. JPCP 

located in colder freeze climates 

exhibited significantly greater joint 

faulting and greater joint spalling.

• PCC in situ temperature: The annual in 

situ PCC temperature (averaged over 

the year) had a significant impact on 

fatigue cracking, joint spalling, and 

smoothness loss. While increased 

PCC temperature correlates well with 

temperature variables such as thermal 

gradient, climate zone, freeze/thaw 

cycles, and frost depth, the following 

observations were made:

• Increased PCC temperature 

resulted in increased fatigue 

transverse cracking.

• Increased PCC temperature 

(warmer climate) resulted in less 

transverse joint spalling.

• Increased PCC temperature 

(warmer climate) resulted in 

greater smoothness loss.

• Freeze/thaw cycles: Higher numbers 

of freeze/thaw cycles resulted in 

significantly greater joint faulting and 

joint spalling over 15 years.

• Precipitation: Lower annual precipitation resulted in increased fatigue 

cracking of JPCP. Drier climates 

resulted in greater thermal gradients 

and higher moisture gradients in 

concrete slabs. This contributes to 

higher upward curling and top-ofslab tensile stresses that, combined 

with load-associated stresses, cause 

additional fatigue damage at the top 

of the slab with corresponding topdown cracking.

• Subgrade soil: Subgrade-related 

variables had a significant impact on 

fatigue cracking, joint faulting, and 

smoothness loss. The only distress 

not affected was joint spalling.

The coarser grained the subgrade 

was, the greater the fatigue transverse 

cracking was. This result is difficult to 

explain other than that coarse-grained 

soil typically has a higher modulus 

that leads to higher curling stresses 

at the top of the slab and increased 

top-down cracking.
11

The higher the percent clay content 

is, the greater the joint faulting is. 

This may be related to pumping and 

erosion of the subgrade through 

the unbound aggregate base course 

layers beneath the PCC slab.

Summary

An estimate was made of the proportion 

of pavement damage caused by 

environmental factors using comparisons of pavement damage of low traffic 

SPS-8 performance with higher traffic 

“companion” SPS and GPS. Results for 

flexible pavement showed that 36 percent 

of total damage caused when loaded 

under normal traffic levels was related 

to environment (subgrade and climate 

variables). Results for rigid pavement 

showed that 24 percent of total damage 

caused when loaded under normal 

traffic levels was related to environment 

(subgrade and climate variables) after 

15 years of service. Therefore, additional 

attention to AC, PCC, aggregate base 

course, and subgrade layer materials 

durability for a specific climatic zone 

would provide significantly improved 

performance. In addition, improved 

thickness design for AC and PCC layers 

would also provide significantly improved 

performance. (For example, AC thickness 

was very significant in reducing fatigue 

cracking in warm climates but less so in 

cold climates.)

In addition, many results of interest to 

pavement and materials engineers 

were obtained through analysis of the 

performance of the SPS-8 and other 

SPS and GPS companion sections. One 

of many interesting findings was that 

the occurrence of transverse cracking of 

AC pavement was significantly higher 

for companion pavements subjected to 

higher traffic loadings (SPS-1 and GPS-1) 

than under low traffic loadings (SPS-8). 

Transverse cracks also frequently occurred 

in non-freeze climate zones where they 

were not expected. The final report 

documents some suggested findings from 

this study to improve pavement design 

and materials selection to minimize 

distress and to maximize performance in 

various critical climatic regions. 

References

1. Federal Highway Administration. (2013). 

LTPP InfopaveTM, Long-Term Pavement 

Performance Program, Federal Highway 

Administration, Washington, DC, 

obtained from: https://infopave.fhwa.

dot.gov, last accessed January 30, 2015.

2. American Association of State 

Highway and Transportation Officials. 

(2015). AASHTOWareTM Pavement ME 

Design, American Association of State 

Highway and Transportation Officials, 

Washington, DC, obtained from: http://

www.aashtoware.org/Pavement/Pages/

default.aspx, last accessed July 1, 2015.
12

Researchers—Leslie Titus-Glover, Michael I. Darter, and Harold Von Quintus, 

Applied Research Associates, Inc.

Distribution—This TechBrief is being distributed according to a standard 

distribution. Direct distribution is being made to the FHWA Divisions and Resource 

Center.

Availability—This TechBrief is being distributed according to a standard 

distribution. Direct distribution is being made to the FHWA Divisions and Resource 

Center.

Key Words—LTPP, pavement performance, damage, environmental factors, JPCP, 

ACP, subgrade, SPS-8, truck loadings, cost allocation.

Notice—This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The U.S. 

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document. The U.S. Government does not endorse products or manufacturers. 

Trademarks or manufacturers’ names appear in this report only because they are 

considered essential to the objective of the document.

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DECEMBER 2016 FHWA-HRT-16-078

HRDI-30/12-16(500)E