Mississippi Code Title 77. Public Utilities and Carriers § 77-9-233

(a) to railroads whose principal business is hauling logs;

(b) to locomotive engines running for coal or water, doubling hills, returning from trains when broken into, or going to or returning from trains in the yard limits of terminal stations;

(c) to engines engaged in regular switching service in yards or road engines switching at intermediate stations; or

(d) to any locomotive engines in cases of washouts, wrecks, or when going to the assistance of engines so disabled as to block the main track of a railroad.