U.S. Tier 3 standards phase in from 2017–2025 and apply to vehicles up to 14,000 lbs gross vehicle weight. Once fully phased-in, Tier 3 tailpipe PM and NOx+NMOG emission limits for light- and medium-duty passenger vehicles are the most stringent in the world. IEA/IRENA Global Renewable Energy Policies and Measures Database © OECD/IEA and IRENA, [November 2020]