The main purpose of this legislative text is to allow Congress to disapprove a specific rule set by the Environmental Protection Agency (EPA) regarding greenhouse gas emissions standards for heavy-duty vehicles. This rule is known as "Phase 3" and aims to regulate emissions from larger vehicles to help combat climate change. The key provision of this resolution is a formal disapproval of the EPA's Phase 3 emissions standards. By passing this resolution, Congress is stating that the rule will not be enforced and will have no legal effect.