49 CFR 230.116: Oil tanks.

The oil tanks on oil burning steam locomotives shall be maintained free from leaks. The oil supply pipe shall be equipped with a safety cut-off device that:

(a) Is located adjacent to the fuel supply tank or in another safe location;

(b) Closes automatically when tripped and that can be reset without hazard; and

(c) Can be hand operated from clearly marked locations, one inside the cab and one accessible from the ground on each exterior side of the steam locomotive.