According to various aspects, exemplary embodiments are disclosed of devices, systems, and methods related relaying voice messages to operator control units of a locomotive. In an exemplary embodiment, an operator control unit generally includes a user interface configured to receive one or more commands from an operator for controlling a locomotive, a wireless communication interface configured to transmit data to and receive data from a locomotive control unit of the locomotive, and memory configured to store multiple voice messages corresponding to the locomotive. The operator control unit also includes a processor configured to receive a voice message number from the locomotive control unit of the locomotive via the wireless communication interface, retrieve one of the multiple stored voice messages from memory corresponding to the received voice message number, and transmit the retrieved voice message to an earpiece of the operator via a wired transmission and/or near-field wireless transmission.