49 CFR § 525.4 - Definitions.

---
identifier: "/us/cfr/t49/s525.4"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "49 CFR § 525.4 - Definitions."
title_number: 49
title_name: "Transportation"
section_number: "525.4"
section_name: "Definitions."
chapter_name: "NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
part_number: "525"
part_name: "EXEMPTIONS FROM AVERAGE FUEL ECONOMY STANDARDS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "15 U.S.C. 2002; 49 CFR 1.50."
regulatory_source: "42 FR 38376, July 28, 1977, unless otherwise noted."
cfr_part: "525"
---


# 525.4 Definitions.

(a) *Statutory terms.* (1) The terms *fuel,* *manufacture,* *manufacturer,* and *model year,* are used as defined in section 501 of the Act.

(2) The terms *average fuel economy, fuel economy,* and *model type* are used as defined in 40 CFR 600.002-77.

(3) The term *automobile* means a vehicle determined by the Administrator under 49 CFR part 523 to be an automobile.

(4) The term *passenger automobile* means an automobile determined by the Administrator under 49 CFR part 523 to be a passenger automobile.

(5) The term *customs territory of the United States* is used as defined in 19 U.S.C. 1202.

(b) *Other terms.* (1) The term *base level* and *vehicle configuration* are used as defined in 40 CFR 600.002-77.

(2) The term *vehicle curb weight* is used as defined in 40 CFR 85.002.

(3) The term *interior volume index* is used as defined in 40 CFR 600.315-77.

(4) The term *frontal area* is used as defined in 40 CFR 86.129-79.

(5) The term *basic engine* is used as defined in 40 CFR 600.002-77(a)(21).

(6) The term *designated seating position* is defined in 49 CFR 571.3.

(7) As used in this part, unless otherwise required by the context:

*Act* means the Motor Vehicle Information and Cost Savings Act (Pub. L. 92-513), as amended by the Energy Policy and Conservation Act (Pub. L. 94-163);

*Administrator* means the Administrator of the National Highway Traffic Safety Administration;

*Affected model year* means a model year for which an exemption and alternative average fuel economy standard are requested under this part;

*Production mix* means the number of passenger automobiles, and their percentage of the petitioner's annual total production of passenger automobiles, in each vehicle configuration which a petitioner plans to manufacture in a model year; and

*Total drive ratio* means the ratio of an automobile's engine rotational speed (in revolutions per minute) to the automobile's forward speed (in miles per hour).

(Authority: Sec. 301, Pub. L. 94-163, 89 Stat. 871 (15 U.S.C. 2002); delegation of authority at 41 FR 25015, June 22, 1976; sec. 9, Pub. L. 89-670, 80 Stat. 981 (49 U.S.C. 1657))

[42 FR 38376, July 28, 1977, as amended at 44 FR 55579, Sept. 27, 1979]