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The quality of highway construction translates directly to performance. The better the quality,
the better the performance and greater the life of the infrastructure product.
But how can an agency incentivize good quality while allowing for contractor innovation;
and recover loss of service life by disincentivizing marginal quality in a rational and defendable manner?
That is where Performance Related Specifications come in.
Performance Related Specifications provide a bridge between construction quality and
long-term performance as assessed during and immediately following construction.
Performance Related Specifications are Improved Quality Assurance Specifications,
wherein the quality characteristics used for acceptance are related to the performance
of the in-place product through mathematical modeling.
They represent a progression toward increased use of properties that are more indicative
of how the finished product will perform over time.
The performance models are used to develop a rational basis for establishing targets
and making price adjustments.
Performance-Related Specifications are closely related to performance-based specifications,
but with one difference.
Performance-based specifications only use fundamental engineering properties as quality
characteristics, whereas Performance Related Specifications may also use quality characteristics
that are related to fundamental engineering properties to model performance.
For example: asphalt mat density and its modeled effect
on rutting and fatigue cracking in asphalt pavements, and
entrained air content and its modeled effect on freeze-thaw damage and spalling in concrete pavements.
By allowing for the use of both fundamental engineering properties and non-fundamental
properties as quality characteristics, Performance Related Specifications provides flexibility
in the development and use of test procedures and performance models.
The following are the key steps involved in using Performance Related Specifications
STEP 1: The first step in developing and using PRS
occurs prior to project letting and includes establishing performance criteria in terms
of the distress indicators to be modeled.
STEP 2: The agency identifies acceptance quality characteristics,
or AQCs, that are to be evaluated, including the sampling techniques and test methods to be used.
This step also includes establishing target values for each AQC.
STEP 3: A software program, specifically designed
to model performance is used to simulate the long-term performance considering each AQC.
The performance models predict distress indicators for a range of possible AQC values.
STEP 4: For each AQC, the agency uses the difference
in predicted performance between each potential as-constructed AQC value, and the as-designed
AQC value to establish payment provisions, based on agency-established valuations for
that performance difference.
STEP 5: The payment provisions are incorporated into
the project specifications before the project is let.
The specifications include the sampling and testing plans and the procedure for combining
pay factors applicable to various AQCs.
The specifications should also include provisions for non-conforming results that fall beyond
the range of the PRS payment provisions.
STEP 6: During construction, proper quality assurance
practices are performed by the contractor.
The AQCs for each sublot and lot are sampled and tested per the sampling and testing plan, by the agency.
STEP 7: For each lot, the measured values of the AQCs
are used with the payment provisions from the specifications to compute the pay factor
applicable to each AQC.
The pay factors for various AQCs are combined as outlined in the specifications.
STEP 8: The contractor is awarded an incentive or
assessed a disincentive for that lot based on the combined pay factor applied to the specified bid item.
The benefits of implementing Performance Related Specifications at an agency include the following:
They provide a direct linkage between design expectations and construction quality.
For example, the specified design becomes the target, which when achieved, results in
the contractor being paid 100 percent of the bid price for a lot.
When exceeded, results in the contractor being paid an incentive commensurate with agency
valuation of the improved performance.
Performance Related Specifications transfer some of the product performance risk from
agency to the contractor in return for limiting prescriptive requirements, allowing the contractor
to have more control, to be more innovative, and to be more competitive.
In the long run, this will result in better and more efficient construction practices,
provide improvements to pavement life, and thus reduce long-term costs to the agency
and traveling public.
Performance Related Specifications also allow for providing incentives for reduced variability
through performance modeling.
For a contractor to succeed using Performance Related Specifications and maximize profits,
they need to focus on good quality control practices, exceed target quality, and improve consistency.
Performance Related Specifications testing focuses on key AQCs that relate to the long-term
performance of the pavement.
And give contractors more control, more responsibility, and more flexibility to select materials,
techniques, and procedures to improve the quality or economy, or both, of the final product.
As compared to conventional quality assurance specifications, Performance Related Specifications
represents a shift towards providing pay that is commensurate with expected performance
and a further shift of risk and control from agency to contractor.
To learn more about Performance Related Specifications,
visit our website at fhwa.dot.gov/research
Help with writing and implementing specifications and with construction quality assurance are
available through the FHWA Resource Center, and through NHI Courses 134001,
Principles and Applications of Highway Construction Specifications,
and 134064, Transportation Construction Quality Assurance.
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