Which definition describes a operational area that includes both interlocking and cab signals?

The definition that describes an operational area that includes both interlocking and cab signals is Centralized Traffic Control (CTC). CTC is a system used in railroads that allows for the centralized management of train movements over a network of tracks. This system integrates both interlocking, which controls the signals and switches to ensure safe train movements through junctions, and cab signals, which provide vital information directly to train crews in the locomotive.

In essence, CTC enhances safety and operational efficiency by allowing real-time control and communication between train crews and centralized dispatchers. This setup is crucial for maintaining the flow of train movements, particularly in busy rail corridors where multiple trains may operate in close proximity to each other.

In contrast, the other options do not accurately reflect the combination of interlocking and cab signals. Inaccessible track refers to areas that cannot be accessed for service or maintenance. Main track rules specifically govern the operation and safety protocols on the main tracks, and working limits involve restrictions for engineering or maintenance work. None of these concepts encompass the functionality and operational control provided by Centralized Traffic Control.