Comment submitted by National Association of Clean Air Agencies (NACAA)

Summary: The National Association of Clean Air Agencies (NACAA) opposes the proposed two-year delay in the phase-in schedule for Tier 4 criteria pollutant standards for light-duty and medium-duty vehicles. They argue that the delay undermines state and local efforts to meet National Ambient Air Quality Standards (NAAQS) and that the standards are already technologically achievable.