This rulemaking would revise 49 CFR part 574, to require a three-symbol plant code and allow the agency to continue to assign unique plant codes to manufacturers who apply. In January 1971, the requirement for a Tire Identification Number (TIN) was established in 49 Code of Federal Regulations (CFR) part 574.5, Tire Identification and Recordkeeping, in part to identify tires during safety recalls, and as Federal motor vehicle safety standards for tires were created, part 574.5 became a requirement by reference. The regulation specifies, in part, a two-symbol manufacturer's identification mark, herein called the plant code. Under part 574.6, the agency has the authority to assign new tire plant codes to manufacturers who apply, but the pool of new two-symbol tire plant codes has been depleted.