---
kind: "section"
citation: "49 U.S.C. § 31147"
title: "49"
title_heading: "Transportation"
number: "31147"
heading: "Limitations on authority"
release: "119-102"
date: "2026-07-12"
url: "https://uscodex.org/usc/49/31147"
units:
  - "Subtitle VI — Motor Vehicle and Driver Programs"
  - "Part B — Commercial"
  - "Chapter 311 — Commercial Motor Vehicle Safety"
  - "Subchapter III — Safety Regulation"
---

# §31147. Limitations on authority

- (a) **Traffic Regulations.—** This subchapter does not authorize the Secretary of Transportation to prescribe traffic safety [regulations](/usc/49/31132.md?p=7) or preempt [State](/usc/49/31101.md?p=4) traffic [regulations](/usc/49/31132.md?p=7). However, the Secretary may prescribe traffic [regulations](/usc/49/31132.md?p=7) to the extent their subject matter was regulated under parts 390–399 of title 49, Code of Federal [Regulations](/usc/49/31132.md?p=7), on October 30, 1984.
- (b) **Regulating the Manufacturing of Vehicles.—** This subchapter does not authorize the Secretary to regulate the manufacture of [commercial motor vehicles](/usc/49/31101.md?p=1) for any purpose, including [fuel economy](/usc/49/32901.md?p=a-11), safety, or emission control.

## Source credit

(Pub. L. 103–272, § 1(e), July 5, 1994, 108 Stat. 1013.)

## Notes

| Historical and Revision Notes |  |  |
| --- | --- | --- |
| Revised<br>Section | Source (U.S. Code) | Source (Statutes at Large) |
| 31147(a) | 49 App.:2519(a). | Oct. 30, 1984, Pub. L. 98–554, § 229, 98 Stat. 2853. |
| 31147(b) | 49 App.:2519(b). |  |

In subsection (a), the word “prescribe” is substituted for “establish or maintain” for consistency in the revised title and with other titles of the United States Code.