A spring applied parking brake assembly for a railway vehicle is provided which automatically activates upon removal of a railway car from the pneumatic braking system of the railway vehicle. The spring applied parking brake assembly comprises a casing which is mounted on or within the braking system, typically alongside the air cylinder. This casing contains a spring member and a piston assembly, both of which are mounted for longitudinal movement within the casing upon the application and/or removal of pneumatic pressure within the casing. The piston assembly includes a piston rod which is associated with the force transfer lever of the braking system such that upon a removal of pneumatic pressure within the casing, longitudinal movement of the piston rod causes this force transfer lever to rotate and apply a force to at least one force transmitting member in the vehicle braking system to initiate a brake application. An arrangement or system for installing the spring applied parking brake assembly within a railway vehicle braking system is also provided.