A manifold for providing hydraulic fluid to a hydraulically actuated device of a blowout preventer, the manifold comprising: a first and a second subsea valve module (62a, 62b), each comprising: an inlet (14a, 14b) of the manifold configured to receive hydraulic fluid from a fluid source; an outlet (22a, 22b) of the manifold in selective fluid communication with the inlet; a vent configured to direct hydraulic fluid that flows through the vent to at least one of a reservoir and a subsea environment; and one or more subsea valve assemblies, each changeable between: a first state in which the outlet is in fluid communication with the inlet; a second state in which the outlet is in fluid communication with the vent; and a third state in which neither the inlet nor the vent is in fluid communication with the outlet; where the inlet of the first subsea valve module is configured to receive hydraulic fluid from a first fluid source, and the inlet of the second subsea valve module is configured to receive hydraulic fluid from a second fluid source that is separate from the first fluid source; where the outlet of the first subsea valve module is configured to be in simultaneous fluid communication with the outlet of the second subsea valve module and an actuation port of the hydraulically actuated device; where, for each of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises: a first two-way valve configured to selectively allow fluid communication from the inlet to the outlet; and a second two-way valve configured to selectively divert hydraulic fluid from the outlet to the vent; and where, for each of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises: a first isolation valve in fluid communication between the respective fluid source and the respective first two-way valve to selectively block fluid communication between the fluid source and the first two-way valve, and/or a second isolation valve in fluid communication between the respective vent and the respective second two-way valve to selectively block fluid communication between the second two-way valve and the vent; and where, for at least one of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises a bi-stable valve. a first and a second subsea valve module (62a, 62b), each comprising: an inlet (14a, 14b) of the manifold configured to receive hydraulic fluid from a fluid source; an outlet (22a, 22b) of the manifold in selective fluid communication with the inlet; a vent configured to direct hydraulic fluid that flows through the vent to at least one of a reservoir and a subsea environment; and one or more subsea valve assemblies, each changeable between: a first state in which the outlet is in fluid communication with the inlet; a second state in which the outlet is in fluid communication with the vent; and a third state in which neither the inlet nor the vent is in fluid communication with the outlet; an inlet (14a, 14b) of the manifold configured to receive hydraulic fluid from a fluid source; an outlet (22a, 22b) of the manifold in selective fluid communication with the inlet; a vent configured to direct hydraulic fluid that flows through the vent to at least one of a reservoir and a subsea environment; and one or more subsea valve assemblies, each changeable between: a first state in which the outlet is in fluid communication with the inlet; a second state in which the outlet is in fluid communication with the vent; and a third state in which neither the inlet nor the vent is in fluid communication with the outlet; a first state in which the outlet is in fluid communication with the inlet; a second state in which the outlet is in fluid communication with the vent; and a third state in which neither the inlet nor the vent is in fluid communication with the outlet; where the inlet of the first subsea valve module is configured to receive hydraulic fluid from a first fluid source, and the inlet of the second subsea valve module is configured to receive hydraulic fluid from a second fluid source that is separate from the first fluid source; where the outlet of the first subsea valve module is configured to be in simultaneous fluid communication with the outlet of the second subsea valve module and an actuation port of the hydraulically actuated device; where, for each of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises: a first two-way valve configured to selectively allow fluid communication from the inlet to the outlet; and a second two-way valve configured to selectively divert hydraulic fluid from the outlet to the vent; and a first two-way valve configured to selectively allow fluid communication from the inlet to the outlet; and a second two-way valve configured to selectively divert hydraulic fluid from the outlet to the vent; and where, for each of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises: a first isolation valve in fluid communication between the respective fluid source and the respective first two-way valve to selectively block fluid communication between the fluid source and the first two-way valve, and/or a second isolation valve in fluid communication between the respective vent and the respective second two-way valve to selectively block fluid communication between the second two-way valve and the vent; and where, for at least one of the subsea valve modules, at least one of the one or more subsea valve assemblies comprises a bi-stable valve.