The Administrator shall promptly establish at least one testing center (in addition to the testing centers existing on
November 15, 1990) located at a site that represents high altitude conditions, to ascertain in a reasonable manner whether, when in actual use throughout their useful life (as determined under
section 7521(d) of this title), each class or category of vehicle and engines to which regulations under
section 7521 of this title apply conforms to the emissions standards established by such regulations. For purposes of this subsection, the term “high altitude conditions” refers to high altitude as defined in regulations of the Administrator in effect as of
November 15, 1990.