What is the consequence of a signal power failure on the subway system?

The consequence of a signal power failure in a subway system is that stop arms will move to the tripping position. This is an important safety feature designed to prevent accidents and ensure the safe operation of trains. When there is a loss of power to the signal system, the stop arms engage to indicate that the train must stop, effectively controlling train movement in the absence of operational signals.

In scenarios where signal systems fail, ensuring that trains do not proceed unsafely through potentially hazardous areas is critical. The activation of stop arms during a power failure helps to maintain safety protocols, giving operators the visual cue that they should stop and assess the situation before proceeding.

Other outcomes, such as increased train speeds or signal lights remaining green, would compromise safety. Automated announcements failing can occur with power outages, but they do not directly impact train operations in the way that a stop arm would. Thus, the movement of stop arms to the tripping position is a crucial and immediate response to a signal power failure, ensuring the safety of both trains and passengers in the system.