Abstract: A deceleration control system in which an operator's brake valve device provides corresponding pneumatic and electric brake demand signals in accordance with a selected handle position, the pneumatic brake demand signal controlling a blending valve device to establish the maximum level of friction braking, while the electric brake demand signal is compared to an actual rate of retardation signal to provide a rate error signal that acts via a transducer of the blending valve to reduce the effective friction braking to the extent that the rate of retardation exceeds the brake demand. The electric brake demand signal is limited in accordance with a speed/adhesion characteristic, while a further circuit slip modulates the brake demand signal.