We hire radios specifically programmed for shunting trains. Rather then having to transmit vocally every few seconds we programme in a “comfort tone”. Once the intention to move the train has been made, the user presses the comfort tone button which sounds every few seconds telling the driver to start moving the train.
Should the button be released the comfort tone stops instantaneously, telling the driver to stop the train. This system is preferable to voice command as (dependent on how far the train is moving) the user could potentially be transmitting vocal commands every few seconds for a long period of time.