What immediate action should be taken if the brakes fail during pushback?

Applying the emergency brakes is the most crucial action to take if the brakes fail during pushback. Emergency brakes are designed specifically to provide an additional layer of safety in situations where regular braking systems malfunction. Engaging the emergency brakes could help to bring the aircraft to a stop, or at least slow it down enough to regain control.

This action is vital because it addresses the failure of the primary braking system directly, reducing the risk of an accident or collision during the critical phase of pushback. By using the emergency brakes, ground personnel can manage the situation more effectively and maintain safety on the ramp, which is essential in aircraft operations.

The other options, while they may seem like potential responses, do not provide the immediate control necessary in a braking failure scenario. Increasing throttle would further accelerate the aircraft, risking a more dangerous situation. Signaling for assistance is important, but it does not replace the need for immediate action to prevent an accident. Continuing to move until a stop is safe could lead to loss of control, endangering personnel and equipment on the ramp. Thus, applying the emergency brakes is the correct and safest response to a brake failure during pushback.