A hydraulic braking system for use in a vehicle employing both hydraulic and regenerative braking including a master cylinder with a reservoir inlet port and an outlet port. The outlet port is responsive to vehicle operator applied brake pedal pressure to close the inlet port and provide pilot pressure at the outlet port which is selectively coupled by a valve (57) to a hydraulic pedal simulator and to a control valve. The control valve provides boost hydraulic pressure from a pressure source to a vehicle wheel brake actuator in proportion to the pressure differential between the pilot pressure and a hydraulic pressure which is proportional to regenerative braking torque. This allows the power train controller to independently request different levels of regeneration on the two axles.