The DEF Act aims to maintain regulatory stability for motor vehicles and engines by limiting stringent emissions standards.

The DEF Act, or Diesel Engine Flexibility Act, amends the Clean Air Act to ensure regulatory stability for motor vehicles and engines. It prohibits the Environmental Protection Agency from implementing more stringent emissions standards for on-road and nonroad vehicles and engines for ten years. During this period, the EPA can only promulgate standards that apply for at least three model years and take effect five years after promulgation. The Act also provides a safe harbor for certain emissions control strategies if implemented according to specified guidance documents.

The DEF Act aims to maintain regulatory stability for motor vehicles and engines by limiting stringent emissions standards.

The DEF Act, or Diesel Engine Flexibility Act, amends the Clean Air Act to ensure regulatory stability for motor vehicles and engines. It prohibits the Environmental Protection Agency from implementing more stringent emissions standards for on-road and nonroad vehicles and engines for ten years. During this period, the EPA can only promulgate standards that apply for at least three model years and take effect five years after promulgation. The Act also provides a safe harbor for certain emissions control strategies if implemented according to specified guidance documents.