The present invention relates generally to hydraulic systems for actuating a vehicle braking system. More specifically, the present invention relates to a hydraulic system that uses the gravity-generated pressure in a load-bearing hydraulic cylinder to provide hydraulic pressure to a parking brake, emergency brakes, or service brake when properly modulated or other service. The present invention further relates to a system to reduce through dissipation or utilization the available gravity-generated hydraulic pressure so as to deploy a ground engaging drag-brake of a vehicle.