This synthesis describes the current quality assurance (QA) practices of state and federal departments of transportation with regard to highway materials and construction, including soils and embankments, aggregate base and subbase, hot-mix asphalt, portland cement concrete paving, and portland cement concrete structures. The report focuses on the strategies and practices used by agencies to ensure quality. Because QA is viewed differently among the agencies, methods and procedures that constitute the QA programs of highway agencies also differ significantly. This synthesis summarizes these methods and procedures to the greatest extent feasible, including information on quality control, acceptance, independent assurance, and training/certification. It includes discussion of statistically based specifications, QA specifications, FHWA QA procedures for construction (complying with 23 CFR 637), performance-related specifications, optimal procedures for QA specifications, the use of consultants, and resource allocation. This synthesis report contains information developed from a literature review of QA practices. The results of a survey questionnaire that detail the current state of the practice of state, federal, and Canadian QA programs supplement the literature review. To better understand the terms used in this synthesis, terms related to QA programs and specification are defined, as adapted from TRB's "Glossary of Highway Quality Assurance Terms." (Author/publisher) This report may be accessed by Internet users at http://www.trb.org/publications/nchrp/nchrp_syn_346.pdf
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