# Improvements for Heavy-Duty Engine and Vehicle Fuel Efficiency Test Procedures, and Other Technical Amendments
> **US Department of Transportation** · Final rule. · Published 2024-03-15 · Effective 2024-05-14 · 89 FR 18808
## Document
- **Document number:** 2024-05010
- **Category:** other
- **Sub-agency:** US Department of Transportation
- **Federal Register citation:** 89 FR 18808
- **CFR reference:** 49 CFR 535
- **Publication date:** 2024-03-15
- **Effective date:** 2024-05-14
- **DOT docket:** NHTSA-2020-0079
## Abstract

The National Highway Traffic Safety Administration (NHTSA) is finalizing minor technical amendments to the test procedures for heavy- duty engines and vehicles to improve accuracy and reduce testing burden. These amendments affect the certification procedures for fuel efficiency standards and related requirements. These amendments increase compliance flexibility, harmonize with other requirements, add clarity, correct errors, and streamline the regulations. Given the nature of these changes, NHTSA does not expect either significant environmental impacts or significant economic impacts for any sector.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2024/03/15/2024-05010/improvements-for-heavy-duty-engine-and-vehicle-fuel-efficiency-test-procedures-and-other-technical)
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