A vehicle brake circuit including a brake actuator, a manually operable valve, an electrically operable valve and a fluid reservoir for the supply of fluid to the actuator. The manually operated valve may be connected to the fluid reservoir either directly or indirectly through the electrically operable valve, when its position blocks a direct fluid connection with the fluid reservoir. The electrically operated valve controls activation or deactivation of the actuator except when the mechanically operated valve is in an unblocked position and overrides the electrically operated valves control of the actuator.