40 CFR § 92.1006
Refueling requirements
June 9, 2020
(a) Refueling equipment used by a locomotive operator for locomotives fueled with a volatile fuel shall be designed in such a manner so as not to render inoperative or reduce the effectiveness of the controls on the locomotive that are intended to minimize the escape of fuel vapors.
(b) Hoses used to refuel gaseous-fueled locomotives shall not be designed to be bled or vented to the atmosphere under normal operating conditions.