The National Academies

NCHRP Synthesis 20-05/Topic 06-02 [Final (Synthesis)]

Statistically Oriented End-Result Specifications
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data

The beginning of the trend toward statistical specifications for highway construction was probably the AASHO Road Test. A number of agencies have conducted studies on statistical concepts in highway specifications and many have used or experimented with statistically oriented end-result specifications. End-result specifications (ERS) are used instead of "recipe" or method specifications. Under ERS, an agency monitors the contractor's control of the process that produces a material or item of construction and accepts or rejects the end product. Thus, the end-result specification places the entire responsibility for quality control on the contractor. A completely statistically oriented end-result specification should include lot size, point of sampling, method of random sampling, number of samples to be taken on each lot, method of test, target value of measured characteristic, realistic tolerances and the action to be taken if quality requirements are not met. 

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