How are parking brakes held in the released position?

Parking brakes are typically held in the released position by a manual mechanism. This often involves a valve or lever that must be actively pushed in or pulled to disengage the parking brake. This design ensures that the brake remains firmly in the released position until the driver decides to engage it again.

In contrast, hydraulic systems, while they can be involved in the functioning of other brake types, do not play a role in holding parking brakes released. Parking brakes are designed to engage when needed, providing security for a stationary vehicle, and rely on a manual mechanism rather than maintaining continuous hydraulic pressure.

The option related to automatic release when the vehicle moves is also incorrect, as parking brakes are meant to remain engaged until the driver manually releases them, ensuring the vehicle does not roll unintentionally. Hence, the requirement for a manual input to keep parking brakes released aligns with the safety standards and operational procedures of these braking systems.