19 C.F.R. § 115.8 – Certifying Authorities responsibilities—road vehicles.

(a) General. Road vehicles may be approved individually or by design type.
(b) Individual approval. The Certifying Authority to whom a road vehicle is submitted for approval shall inspect such road vehicle produced in accordance with the general rules contained in Annex 3 of the TIR Convention, 1975.
(c) Design type approval. The Certifying Authority to whom a road vehicle is submitted for design type approval shall examine the drawings and detailed design specifications submitted with the application for approval. The Certifying Authority shall advise the applicant of any changes that must be made to the proposed design type in order that approval may be granted. The Certifying Authority shall examine one or more vehicles to confirm that such vehicles comply with the technical conditions contained in Annex 2 of the TIR Convention, 1975. The Certifying Authority shall notify the applicant of its decision to grant design type approval, and it shall issue an approval certificate complying with Annexes 3 and 4 of the TIR Convention, 1975.
(d) Supplementary examinations. If a road vehicle approved by design type is the subject of an extended production run under one certificate of approval, the Certifying Authority shall confirm by examination of one or more road vehicles during the manufacturing process, or by other means, that such vehicles continue to meet the approved drawings and detailed design specifications and the technical requirements of Annex 2 of the TIR Convention, 1975.
For the purposes of this section, an extended production run shall be considered a continuous run of many units over long periods of time, as well as a new run following the completion of a previous run.