The precise definition of "operating speed", however, is open to debate. Some sources, such as the AASHTO, have changed their definitions recently to match the common use of the word. In 1994, the AASHTO Green Book defined the operating speed as "the highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section-by-section basis," a definition which a majority of US states still use. In 2001, however, the AASHTO revised their definition for the new edition of the Green Book and defined it as "the speed at which drivers are observed operating their vehicles during free-flow conditions."
US Patent Issued on Aug. 16 for "Method for Setting Image for Standard Operating Speed, and Method for Finding Evaluation Value with Image of Evaluation Subject Data Based on Standard Operating Speed" (Japanese Inventor)
Aug 17, 2011; ALEXANDRIA, Va., Aug. 17 -- United States Patent no. 8,000,997, issued on Aug. 16. "Method for Setting Image for Standard...