Mo. Rev. Stat. § 389.710
All common carriers, their officers, agents and employees operating any railroad in this state are hereby required to maintain lights between sunset and sunrise on all lead switches in yards, where cars are switched in making up or breaking up of trains and maintain lights on switches on main lines where trains are operated at night, except that this section shall not apply to main lines equipped with centralized traffic control signals, interlocking and remote control type of electric signaling, main lines equipped with automatic block signals where a block signal is located one thousand feet or less in advance of a switch or to trailing point switches on double track. The division may, after hearing, authorize or require the substitution for the above enumerated switch lights such other safety devices as it may find proper or necessary.
§ 389.710, RSMo