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53 A p p e n d i x B Specification Types method specifications. Also called recipe or prescriptive specifications, these specifications require the contractor to use specified materials in definite proportions and spe- cific types of equipment and methods to place the material. [TRC E-C074] performance specifications. Can be used as an umbrella term incorporating end-result specifications, performance-related specifications (PRS), performance-based specifications (PBS), and performance warranties and maintenance provi- sions. In the broadest terms, a performance specification defines the performance characteristics of the final product and links them to construction, materials, and other items under the contractor control. [PS Strategic Roadmap 2004] end-result specifications. Require the contractor to take the entire responsibility for supplying a product or an item of construction in exchange for receiving flexibility in the selection of materials, techniques, and procedures. The agencyâs responsibility is to either accept or reject the final product or to apply a pay adjustment to account for the degree of compliance with the specified performance crite- ria, as established through sampling and testing of the final in-place product. [TRC E-C074] quality assurance (QA) specifications. Require contractor quality management and agency acceptance activities throughout the production and placement of a product. Final acceptance of the product is usually based on a ran- dom, statistical sampling of the measured quality level on a lot-by-lot basis for key quality characteristics. Price adjust- ments are generally determined on the basis of a mathemati- cal assessment of the measured variability of the product. [TRC E-C074] performance-related specifications (PRS). QA specifications that ⢠Base acceptance on key materials and construction qual- ity characteristics that have been found to correlate with fundamental engineering properties that can be used to predict subsequent product performance; ⢠Use mathematical models to quantify the relationship between key materials and construction characteristics that lend themselves to acceptance testing at the time of construction; and ⢠Provide rational pay adjustments based on the difference between the as-designed and as-constructed life-cycle cost. Thus far, PRS have been piloted only for concrete pavement. performance-based specifications (PBS) are QA specifica- tions that describe the desired levels of fundamental engineering properties (e.g., resilient modulus, creep properties, and fatigue properties) that are predictors of performance and appear in primary prediction relation- ships (i.e., models that can be used to predict stress, dis- tress, or performance from combinations of predictors that represent traffic, environmental, roadbed, and struc- tural conditions). [TRC E-C074] PBS differ from PRS in that they specify the desired levels of actual funda- mental engineering properties (as opposed to key quality characteristics) as predictors of performance. Further development and validation of predictive models and performance-based test methods are needed to advance PBS, which have thus far not been implemented on high- way construction projects. performance-based maintenance provisions. Incorporate performance indicators and thresholds similar to those found in warranties. However, unlike typical short-term warranties, postconstruction operational and mainte- nance provisions that extend for at least the design life of the facility (i.e., as found on design-build-operate- maintain or public-private partnership projects) are a way to transfer whole-life performance risk to the con- tractor. They provide maximum flexibility with regard to design, construction means and methods, and the repair Definitions
54 and rehabilitation measures that will be necessary over the contract term. warranties. Hold the contractor responsible for product performance over a prescribed postconstruction period, thereby protecting the agency against defective work and premature failure. Warranty provisions incorporate per- formance indicators and thresholds for monitoring the actual performance or condition of the product over time (e.g., performance indicators for an asphalt pavement may include rutting and cracking). While the scope of war- ranted work and performance indicators may not capture all of the factors contributing to performance, they provide a tool to transfer responsibility for performance to the pri- vate sector and ensure that the products of construction meet targeted performance thresholds for part of the life cycle of that product or component. Although warranty provisions of sufficient duration to address long-term per- formance can be developed, bonding issues may limit the practicality of implementing such a specification. project delivery Methods design-bid-build. The traditional delivery system for the public sector in which the owner contracts separately with a designer and contractor. [NHI Course No. 134058] design-build. A project delivery system in which an entity pro- vides both design and construction services under a single contract. [NHI Course No. 134058] performance-based maintenance agreement. A type of con- tract in which payments for the management and mainte- nance of road assets are linked to the contractor successfully meeting or exceeding clearly defined performance indica- tors. [World Bank TN-27] public-private-partnership/concessionaire. A project delivery system in which an entity or developer invests in a project and provides financing and integrated services to design, construct, operate, and maintain a roadway or transporta- tion facility in return for tolls or some other compensation under the operating or concession agreement.
