Which system helps in detecting trains on tracks?

Track circuits are the correct choice for detecting trains on tracks. This system operates by using electrical circuits that are completed when a train occupies a section of track. When the presence of a train interrupts the electrical current, it signals to the control system that the track section is occupied. This method is widely used in rail signaling systems to ensure safety by preventing signals from displaying "clear" when tracks are occupied, thereby helping to manage the movement of trains effectively and prevent collisions.

In contrast, while manual signals can inform train operators of track conditions, they do not provide continuous detection of train presence. GPS tracking, while useful for overall train location and monitoring, relies on satellite data and is not inherently designed for track occupancy detection. Automated controls may aid in train operation but do not specifically address the immediate need for detecting whether a section of track is occupied or not.