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Publication Number:  FHWA-HRT-13-038    Date:  November 2013
Publication Number: FHWA-HRT-13-038
Date: November 2013


Reformulated Pavement Remaining Service Life Framework



Construction triggers are measureable aspects of a pavement's condition that can be used to indicate the need for corrective treatment. Selecting construction triggers is the basis for developing field data collection programs to measure the condition state of pavement segments.

Some considerations that should be taken when selecting construction triggers include the following:


Level of service construction triggers are primarily based on human factor ratings of the pavement serviceability and pavement roughness measurements.

The use of pavement roughness as a primary indicator of level of service is based on the American Association of State Highway Officials (AASHO) Road Test conducted in the 1950s.(4) Participants provided a PSR on a set of test sections whose attributes were also measured using the best available objective technology at the time. A PSI predictive equation was developed to estimate PSR from the objective ratings. The pavement roughness component accounted for about 85 percent of the variation in the PSR ratings, which verified the expectation that pavement roughness was the primary determinant of pavement level of service from a user standpoint and provided a basis to scale the pavement roughness measurement numerics. Although the AASHO Road Test PSI equation also included statistically significant terms for cracking and patching, the pavement industry has evolved to where pavement roughness, expressed in terms of the IRI, is the most common measure of pavement level of service.


The type, extent, and severity of pavement surface distresses are the basic elements used to describe pavement distresses. The fundamental classifications of pavement distress are related to fracture, deformation, and disintegration of the pavement material.While national standards exist for more than 15 possible types of pavement distress attributes for each type of pavement, they are not all typically required for pavement construction decisions. Reducing the number of distresses to a small number of core distresses can reduce field data collection costs. Methods that can be used to create construction triggers based on pavement distress measurements include the following:


Pavement structural considerations are based on certain types of distress and non-destructive pavement deflection testing.

The primary distinction of distresses most often associated with structural pavement damage is those whose mechanism of formation is due to the application of wheel loads. Common distresses associated with pavement structural integrity include cracking in the wheel path (fatigue cracking), corner cracks on jointed PCC pavements, faulting on jointed PCC pavements, punch outs on continuously reinforced concrete pavement, and rutting associated with subgrade and base instability. A secondary consideration is distress types that contribute to the acceleration of structural damage.

While surface cracking can be an indicator of pavement structural damage, some pavement preservation treatments hide surface cracks. Deflection measurements can be used as a diagnostic tool to look below the pavement surface to determine subsurface damage.

Pavement deflection measurements can be interpreted to characterize a variety of pavement structural conditions. The basic concept behind deflection measurements is the measurement of the deflection of the pavement surface under the application of a known load. Information can be obtained from devices that measure the deflection basin at various distances from the load center and from devices that apply multiple load levels at the same measurement point. A comparison of the changes in deflection response and associated computed parameters along a pavement can reveal the extent of damage not yet visible.

Pavement structural information from deflection measurements includes the following:


Safety aspects of a pavement condition are primarily related to friction and hydroplane potential. Pavement friction characteristics are most often characterized using a skid number parameter. These parameters are based on field measurements using locked wheel, limited slip, or yaw mode friction testers. Hydroplane potential is related to the ability of pavement ruts to hold water. The nominal depth of water retained in the ruts can be associated with hydroplane potential based on the speed limit.

Another safety concern is excessive pavement roughness relative to the speed limit. It is possible for localized bumps, dips, faults, and holes in the pavements to negatively influence vehicle control.


One of the simplest construction needs triggers is the time since the last construction treatment. Some agencies have implemented rules on the maximum amount of time between construction events. Time-based rules are intended to reduce field measurement costs and provide a proactive pavement management approach to keep pavements in good condition.


In changing the definition of RSL to one that is related to assessing future construction needs, it is important to identify when roadways need to be expanded by adding new lanes due to traffic growth. These types of rules are generally outside the realm of pavement management, but they should be considered when developing an estimate of future budget needs.


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