Under D/B contracting,4 the design and construction procurements are combined into one fixed-fee contract with a "single point of contact" that is responsible for both design and construction. The D/B contractor (which may be one company or a consortium of design, construction, and project management firms) assumes the "design risk" that detailed design drawings and specifications will be free from error and agrees to construct the project in accordance with its design. The potential benefits of D/B contracting relative to traditional procurement include time savings, cost savings, risk sharing, and quality improvement arising from the synergies created by having one contractor responsible for both functions. The use of D/B performance specifications developed by the public sector, instead of traditional prescriptive specifications, also encourages innovation by the private contractor.
Some D/B contractors are willing to guarantee that they will meet material, workmanship, and other performance guarantees for a specified period of time (typically 5 to 20 years) after the project has been delivered. This type of D/B with warranty approach allocates quality risk to the contractor and reduces the project sponsor's need to conduct inspection and testing during project delivery. A D/B contractor that is willing to provide a warranty for materials or workmanship, or that remains contractually obligated for maintenance after construction, is compelled to complete life-cycle-cost analyses of all design and construction options. This provides an additional potential benefit to the public project sponsor by shifting the risk of project quality to the private contractor.
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4 See 23 C.F.R. 636.103.