What happens when traversing a failed track circuit in release mode?

When traversing a failed track circuit in release mode, it does not trigger the emergency brake application. This is primarily because, in release mode, the track circuit is allowed to operate without imposing strict safety measures that would typically engage the emergency brakes in the event of a failure. A failed track circuit indicates a loss of detection, and in many systems, the response is intended to maintain a higher degree of operational fluidity.

Thus, by not triggering the emergency brakes, the movement can continue provided that other safety protocols or conditions are met, ensuring the operation runs smoothly while still under careful management and monitoring. Keeping trains moving without immediate stops helps to prevent potential disruptions or congestion on the rail network, allowing management to assess and rectify the failure.

In contrast to the other options, where an emergency application or an increase in speed would pose significant safety risks and operational disruptions, the choice of the system allowing for continued movement (without engaging emergency procedures) reflects a designed operational response that emphasizes reliability while maintaining control.