What signifies the speed limit from the car-borne map for ATC systems?

The speed limit from the car-borne map for Automatic Train Control (ATC) systems is indicated by the allowable speed associated with a flashing green or yellow ATC signal. This is crucial because the signals directly communicate to the train's control system the safe operating speeds under current conditions. When a train encounters a flashing green signal, it indicates that the train can proceed at a particular speed without restrictions, while a flashing yellow signal typically warns the engineer to prepare to reduce speed ahead, signifying potential changes in track conditions or upcoming signals.

It is essential to recognize that this signaling system helps maintain safety and efficiency in train operations by providing real-time updates on allowable speeds, thus enhancing overall train control. The other options relate to different aspects of train operation but do not signify the specific speed limits as determined by the car-borne map in the context of ATC systems. Maximum speed limits pertain to the upper speed bounds, minimum operational speeds refer to the lowest speed to keep the system functioning, and emergency speed limits are typically invoked under adverse conditions rather than being a routine part of speed signaling.