---
kind: "section"
citation: "23 U.S.C. § 175"
title: "23"
title_heading: "Highways"
number: "175"
heading: "Carbon reduction program"
release: "119-102"
date: "2026-07-12"
url: "https://uscodex.org/usc/23/175"
units:
  - "Chapter 1 — Federal-Aid Highways"
---

# §175. Carbon reduction program

- (a) **Definitions.—** In this section:
  - (1) **Metropolitan planning organization; urbanized area.—** The terms “metropolitan planning organization” and “[urbanized area](/usc/23/101.md?p=a-36)” have the meaning given those terms in [section 134(b)](/usc/23/134.md?p=b).
  - (2) **Transportation emissions.—** The term “transportation emissions” means carbon dioxide emissions from on-road [highway](/usc/23/101.md?p=a-11) sources of those emissions within a [State](/usc/23/101.md?p=a-28).
  - (3) **Transportation management area.—** The term “transportation management area” means a transportation management area identified or designated by the [Secretary](/usc/23/101.md?p=a-27) under [section 134(k)(1)](/usc/23/134.md?p=k-1).
- (b) **Establishment.—** The [Secretary](/usc/23/101.md?p=a-27) shall establish a carbon reduction program to reduce transportation emissions.
- (c) **Eligible Projects.—**
  - (1) **In general.—** Subject to [paragraph (2)](#c-2), funds apportioned to a [State](/usc/23/101.md?p=a-28) under [section 104(b)(7)](/usc/23/104.md?p=b-7) may be obligated for [projects](/usc/23/101.md?p=a-20) to support the reduction of transportation emissions, including—
    - (A) a [project](/usc/23/101.md?p=a-20) described in [section 149(b)(4)](/usc/23/149.md?p=b-4) to establish or operate a traffic monitoring, management, and control facility or program, including advanced [truck stop electrification systems](/usc/23/101.md?p=a-34);
    - (B) a public transportation [project](/usc/23/101.md?p=a-20) that is eligible for assistance under [section 142](/usc/23/142.md);
    - (C) a [project](/usc/23/101.md?p=a-20) described in [section 101(a)(29)](/usc/23/101.md?p=a-29) (as in effect on the day before the date of enactment of the FAST Act (Public Law 114–94; 129 Stat. 1312)), including the [construction](/usc/23/101.md?p=a-4), planning, and design of on-road and off-road trail facilities for pedestrians, bicyclists, and other nonmotorized forms of transportation;
    - (D) a [project](/usc/23/101.md?p=a-20) described in [section 503(c)(4)(E)](/usc/23/503.md?p=c-4-E) for advanced transportation and congestion management technologies;
    - (E) a [project](/usc/23/101.md?p=a-20) for the deployment of infrastructure-based intelligent transportation systems capital improvements and the installation of vehicle-to-infrastructure communications equipment, including retrofitting dedicated short-range communications (DSRC) technology deployed as part of an existing pilot program to cellular vehicle-to-everything (C–V2X) technology;
    - (F) a [project](/usc/23/101.md?p=a-20) to replace street lighting and traffic control devices with energy-efficient alternatives;
    - (G) the development of a carbon reduction strategy in accordance with [subsection (d)](#d);
    - (H) a [project](/usc/23/101.md?p=a-20) or strategy that is designed to support congestion pricing, shifting transportation demand to nonpeak hours or other transportation modes, increasing vehicle occupancy rates, or otherwise reducing demand for roads, including electronic toll collection, and travel demand management strategies and programs;
    - (I) efforts to reduce the environmental and community impacts of freight movement;
    - (J) a [project](/usc/23/101.md?p=a-20) to support deployment of alternative fuel vehicles, including—
      - (i) the acquisition, installation, or operation of publicly accessible electric vehicle charging infrastructure or hydrogen, natural gas, or propane vehicle fueling infrastructure; and
      - (ii) the purchase or lease of zero-emission [construction](/usc/23/101.md?p=a-4) equipment and vehicles, including the acquisition, [construction](/usc/23/101.md?p=a-4), or leasing of required supporting facilities;
    - (K) a [project](/usc/23/101.md?p=a-20) described in [section 149(b)(8)](/usc/23/149.md?p=b-8) for a diesel engine retrofit;
    - (L) a [project](/usc/23/101.md?p=a-20) described in [section 149(b)(5)](/usc/23/149.md?p=b-5) that does not result in the [construction](/usc/23/101.md?p=a-4) of new capacity; and
    - (M) a [project](/usc/23/101.md?p=a-20) that reduces transportation emissions at port facilities, including through the advancement of port electrification.
  - (2) **Flexibility.—** In addition to the eligible [projects](/usc/23/101.md?p=a-20) under [paragraph (1)](#c-1), a [State](/usc/23/101.md?p=a-28) may use funds apportioned under [section 104(b)(7)](/usc/23/104.md?p=b-7) for a [project](/usc/23/101.md?p=a-20) eligible under [section 133(b)](/usc/23/133.md?p=b) if the [Secretary](/usc/23/101.md?p=a-27) certifies that the [State](/usc/23/101.md?p=a-28) has demonstrated a reduction in transportation emissions—
    - (A) as estimated on a per capita basis; and
    - (B) as estimated on a per unit of economic output basis.
- (d) **Carbon Reduction Strategy.—**
  - (1) **In general.—** Not later than 2 years after the date of enactment of the Surface Transportation Reauthorization Act of 2021, a [State](/usc/23/101.md?p=a-28), in consultation with any metropolitan planning organization designated within the [State](/usc/23/101.md?p=a-28), shall develop a carbon reduction strategy in accordance with this subsection.
  - (2) **Requirements.—** The carbon reduction strategy of a [State](/usc/23/101.md?p=a-28) developed under [paragraph (1)](#d-1) shall—
    - (A) support efforts to reduce transportation emissions;
    - (B) identify [projects](/usc/23/101.md?p=a-20) and strategies to reduce transportation emissions, which may include [projects](/usc/23/101.md?p=a-20) and strategies for safe, reliable, and cost-effective options—
      - (i) to reduce traffic congestion by facilitating the use of alternatives to single-occupant vehicle trips, including public transportation facilities, pedestrian facilities, bicycle facilities, and shared or pooled vehicle trips within the [State](/usc/23/101.md?p=a-28) or an area served by the applicable metropolitan planning organization, if any;
      - (ii) to facilitate the use of vehicles or modes of travel that result in lower transportation emissions per person-mile traveled as compared to existing vehicles and modes; and
      - (iii) to facilitate approaches to the [construction](/usc/23/101.md?p=a-4) of transportation assets that result in lower transportation emissions as compared to existing approaches;
    - (C) support the reduction of transportation emissions of the [State](/usc/23/101.md?p=a-28);
    - (D) at the discretion of the [State](/usc/23/101.md?p=a-28), quantify the total carbon emissions from the production, transport, and use of materials used in the [construction](/usc/23/101.md?p=a-4) of transportation facilities within the [State](/usc/23/101.md?p=a-28); and
    - (E) be appropriate to the population density and context of the [State](/usc/23/101.md?p=a-28), including any metropolitan planning organization designated within the [State](/usc/23/101.md?p=a-28).
  - (3) **Updates.—** The carbon reduction strategy of a [State](/usc/23/101.md?p=a-28) developed under [paragraph (1)](#d-1) shall be updated not less frequently than once every 4 years.
  - (4) **Review.—** Not later than 90 days after the date on which a [State](/usc/23/101.md?p=a-28) submits a request for the approval of a carbon reduction strategy developed by the [State](/usc/23/101.md?p=a-28) under [paragraph (1)](#d-1), the [Secretary](/usc/23/101.md?p=a-27) shall—
    - (A) review the process used to develop the carbon reduction strategy; and
    - (B)
      - (i) certify that the carbon reduction strategy meets the requirements of [paragraph (2)](#d-2); or
      - (ii) deny certification of the carbon reduction strategy and specify the actions necessary for the [State](/usc/23/101.md?p=a-28) to take to correct the deficiencies in the process of the [State](/usc/23/101.md?p=a-28) in developing the carbon reduction strategy.
  - (5) **Technical assistance.—** At the request of a [State](/usc/23/101.md?p=a-28), the [Secretary](/usc/23/101.md?p=a-27) shall provide technical assistance in the development of the carbon reduction strategy under [paragraph (1)](#d-1).
- (e) **Suballocation.—**
  - (1) **In general.—** For each fiscal year, of the funds apportioned to the [State](/usc/23/101.md?p=a-28) under [section 104(b)(7)](/usc/23/104.md?p=b-7)—
    - (A) 65 percent shall be obligated, in proportion to their relative shares of the population of the [State](/usc/23/101.md?p=a-28)—
      - (i) in [urbanized areas](/usc/23/101.md?p=a-36) of the [State](/usc/23/101.md?p=a-28) with an [urbanized area](/usc/23/101.md?p=a-36) population of more than 200,000;
      - (ii) in [urbanized areas](/usc/23/101.md?p=a-36) of the [State](/usc/23/101.md?p=a-28) with an urbanized population of not less than 50,000 and not more than 200,000;
      - (iii) in [urban areas](/usc/23/101.md?p=a-35) of the [State](/usc/23/101.md?p=a-28) with a population of not less than 5,000 and not more than 49,999; and
      - (iv) in other areas of the [State](/usc/23/101.md?p=a-28) with a population of less than 5,000; and
    - (B) the remainder may be obligated in any area of the [State](/usc/23/101.md?p=a-28).
  - (2) **Metropolitan areas.—** Funds attributed to an [urbanized area](/usc/23/101.md?p=a-36) under [paragraph (1)(A)(i)](#e-1-A-i) may be obligated in the metropolitan area established under [section 134](/usc/23/134.md) that encompasses the [urbanized area](/usc/23/101.md?p=a-36).
  - (3) **Distribution among urbanized areas of over 50,000 population.—**
    - (A) **In general.—** Except as provided in [subparagraph (B)](#e-3-B), the amounts that a [State](/usc/23/101.md?p=a-28) is required to obligate under clauses [(i)](#e-1-A-i) and [(ii)](#e-1-A-ii) of paragraph (1)(A) shall be obligated in [urbanized areas](/usc/23/101.md?p=a-36) described in those clauses based on the relative population of the areas.
    - (B) **Other factors.—** The [State](/usc/23/101.md?p=a-28) may obligate the funds described in [subparagraph (A)](#e-3-A) based on other factors if—
      - (i) the [State](/usc/23/101.md?p=a-28) and the relevant metropolitan planning organizations jointly apply to the [Secretary](/usc/23/101.md?p=a-27) for the permission to base the obligation on other factors; and
      - (ii) the [Secretary](/usc/23/101.md?p=a-27) grants the request.
  - (4) **Coordination in urbanized areas.—** Before obligating funds for an eligible [project](/usc/23/101.md?p=a-20) under [subsection (c)](#c) in an [urbanized area](/usc/23/101.md?p=a-36) that is not a transportation management area, a [State](/usc/23/101.md?p=a-28) shall coordinate with any metropolitan planning organization that represents the [urbanized area](/usc/23/101.md?p=a-36) prior to determining which activities should be carried out under the [project](/usc/23/101.md?p=a-20).
  - (5) **Consultation in rural areas.—** Before obligating funds for an eligible [project](/usc/23/101.md?p=a-20) under [subsection (c)](#c) in a rural area, a [State](/usc/23/101.md?p=a-28) shall consult with any regional transportation planning organization or metropolitan planning organization that represents the rural area prior to determining which activities should be carried out under the [project](/usc/23/101.md?p=a-20).
  - (6) **Obligation authority.—**
    - (A) **In general.—** A [State](/usc/23/101.md?p=a-28) that is required to obligate in an [urbanized area](/usc/23/101.md?p=a-36) with an [urbanized area](/usc/23/101.md?p=a-36) population of 50,000 or more under this subsection funds apportioned to the [State](/usc/23/101.md?p=a-28) under [section 104(b)(7)](/usc/23/104.md?p=b-7) shall make available during the period of fiscal years 2022 through 2026 an amount of obligation authority distributed to the [State](/usc/23/101.md?p=a-28) for [Federal-aid highways](/usc/23/101.md?p=a-6) and [highway](/usc/23/101.md?p=a-11) safety [construction](/usc/23/101.md?p=a-4) programs for use in the area that is equal to the amount obtained by multiplying—
      - (i) the aggregate amount of funds that the [State](/usc/23/101.md?p=a-28) is required to obligate in the area under this subsection during the period; and
      - (ii) the ratio that—
        - (I) the aggregate amount of obligation authority distributed to the [State](/usc/23/101.md?p=a-28) for [Federal-aid highways](/usc/23/101.md?p=a-6) and [highway](/usc/23/101.md?p=a-11) safety [construction](/usc/23/101.md?p=a-4) programs during the period; bears to
        - (II) the total of the sums apportioned to the [State](/usc/23/101.md?p=a-28) for [Federal-aid highways](/usc/23/101.md?p=a-6) and [highway](/usc/23/101.md?p=a-11) safety [construction](/usc/23/101.md?p=a-4) programs (excluding sums not subject to an obligation limitation) during the period.
    - (B) **Joint responsibility.—** Each [State](/usc/23/101.md?p=a-28), each affected metropolitan planning organization, and the [Secretary](/usc/23/101.md?p=a-27) shall jointly ensure compliance with [subparagraph (A)](#e-6-A).
- (f) **Federal Share.—** The Federal share of the cost of a [project](/usc/23/101.md?p=a-20) carried out using funds apportioned to a [State](/usc/23/101.md?p=a-28) under [section 104(b)(7)](/usc/23/104.md?p=b-7) shall be determined in accordance with section 120.
- (g) **Treatment of Projects.—** Notwithstanding any other provision of law, a [project](/usc/23/101.md?p=a-20) assisted under this section shall be treated as a [project](/usc/23/101.md?p=a-20) on a [Federal-aid highway](/usc/23/101.md?p=a-6) under this chapter.

## Source credit

(Added Pub. L. 117–58, div. A, title I, § 11403(a), Nov. 15, 2021, 135 Stat. 555.)

## Notes

### Editorial Notes

### References in Text

The date of enactment of the FAST Act, referred to in subsec. (c)(1)(C), is the date of enactment of Pub. L. 114–94, which was approved Dec. 4, 2015.

The date of enactment of the Surface Transportation Reauthorization Act of 2021, referred to in subsec. (d)(1), is the date of enactment of div. A of Pub. L. 117–58, which was approved Nov. 15, 2021.

### Statutory Notes and Related Subsidiaries

### Effective Date

Section effective Oct. 1, 2021, see section 10003 of Pub. L. 117–58, set out as an Effective Date of 2021 Amendment note under section 101 of this title.