40 CFR § 1033.102
Transition to the standards specified in this subpart
June 9, 2020
(a) The Tier 0 and Tier 1 standards of §1033.101 apply for new locomotives beginning January 1, 2010, except as specified in §1033.150(a). The Tier 0 and Tier 1 standards specified in Appendix I of this part apply for earlier model years.
(b) Except as specified in §1033.150(a), the Tier 2 standards of §1033.101 apply for new locomotives beginning January 1, 2013. The Tier 2 standards specified in Appendix I of this part apply for earlier model years.
(c) The Tier 3 and Tier 4 standards of §1033.101 apply for the model years specified in that section.
[81 FR 74004, Oct. 25, 2016]