# 2025-12159: Feds Expand Allowed Variations in Locomotive Wheel Diameters

2025-12159, Expanding Certain Locomotive Wheel Set Diameter Variations, is a Federal Register proposed rule from Transportation Department, Federal Railroad Administration published 2025-07-01 (as of 2026-06-08).

- Canonical: https://policyrisk.com/federal-register/2025-12159
- As of: 2026-06-08
- Plain-text twin of the page above; the HTML and this file carry the same facts.

## Facts
- Document number: 2025-12159
- Title: Expanding Certain Locomotive Wheel Set Diameter Variations
- Type: Proposed Rule
- Agencies: Transportation Department; Federal Railroad Administration
- Citation: 90 FR 28658
- Published: 2025-07-01
- Effective: unknown
- Comments close: not stated
- Significant: no
- Touches household money: no
- Regulation identifier numbers: 2130-AD50
- Last updated: 2026-06-08

## In one line

Feds Expand Allowed Variations in Locomotive Wheel Diameters

## Summary

The FRA is updating rules to allow bigger size differences in locomotive wheels that use AC technology. This change helps railroads use new tech and keeps trains running safely and smoothly. It mainly affects big rail companies and aims to save time and money by letting them be more flexible with wheel sizes.

## Abstract

FRA proposes to amend its locomotive safety regulations to expand the maximum permitted variation in diameter for locomotive wheel sets using alternating current technology, in response to a Class I railroad's May 2019 petition for rulemaking and innovations in traction motor control.

## Effects PRIA read

- Expanded Wheel Diameter Variation for AC Locomotives: benefit, low. The Federal Railroad Administration proposes to allow larger differences in diameter for locomotive wheel sets that use alternating current (AC) technology. This change responds to a Class I railroad's May 2019 petition and is meant to help railroads use new traction motor control technology, keep…

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## Sources
- [2025-12159 on federalregister.gov](https://www.federalregister.gov/documents/2025/07/01/2025-12159/expanding-certain-locomotive-wheel-set-diameter-variations)
- [2025-12159 as published (PDF)](https://www.govinfo.gov/content/pkg/FR-2025-07-01/pdf/2025-12159.pdf)

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Source: PRIA, https://policyrisk.com/federal-register/2025-12159 (as of 2026-06-08).