Expanding Certain Locomotive Wheel Set Diameter Variations
Key claim: Railroads may now operate AC-powered locomotives with a larger difference in wheel diameters on the same wheel set, because newer traction-motor controls can handle that variation without the old safety limit.
Abstract
(Rule · Transportation Department, Federal Railroad Administration) This rule amends FRA’s 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.
Why this matters
The rule loosens a longstanding FRA wheel-mismatch limit for AC-powered locomotives, letting railroads keep wheel sets in service longer between re-truing and reducing shop time. Practically it affects Class I freight fleets that have largely moved to AC traction; safety oversight shifts from a fixed dimensional cap to reliance on modern motor-control electronics.