The Proof is in the Pavement

by Richard M. Weed, New Jersey Dept. of Transp., 1035 Parkway Ave., CN 612, Trenton, NJ 08625,

Serial Information: Civil Engineering—ASCE, 1993, Vol. 63, Issue 8, Pg. 67-69

Document Type: Feature article

Abstract: A technique known as statistical quality assurance (SQA) lets DOTs quantify pavement quality by setting statistical guidelines for the work they will accept. SQA is a distinct departure from cookbook specifications under which contractors were told precisely how to perform each step of construction. Instead SQA gives contractors latitude to use their expertise, and relies on statistical and mathematical concepts to determine if the end-result meets a predetermined specification. A key to SQA is understanding that for many highway items it may not be possible to define a single level of quality that separates acceptable and unacceptable work. Instead, it is necessary to define an acceptable quality level that is clearly satisfactory, and a rejectable quality level that is so seriously deficient that removal and replacement (or other corrective action) is warranted. In between these two extremes is a gray area of quality—too good to replace, but not good enough to accept for full price. Adjusted pay clauses provide a way for states to accept marginally defective items for a prearranged level of reduced payment. Conversely, many agencies have also sweetened the pot for contractors, using positive incentives that provide bonuses for quality that substantially exceeds the level defined as acceptable. For example, New Jersey may pay up to 103% of contract value for extremely high-quality work. Governing material properties such as pavement strength, thickness and riding quality, SQA has proven to be extremely effective within a number of transportation agencies. About half the states have SQA programs in place and another 25% have statistical specifications in some form of development.

Subject Headings: Design | Guidelines | Pavements | Quality control | Statistics |

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