A braking system comprising an anti-lock vehicle braking system for a vehicle having a pair of drive wheels (13, 14), the wheels of said pair being disposed on opposite sides of the vehicle, comprising a wheel speed sensor (17, 18) for each wheel (13, 14), a controller (19) responsive to wheel speed signals from said two wheel speed sensors (17, 18) for sensing skid conditions at said wheels (13, 14) and for generating skid control instructions, a wheel brake (23, 24) for each wheel (13, 14), responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto, a common supply line (37), for supplying a common brake pressure for both of said brakes from a fluid pressure supply valve means (38) in accordance with a brake demand signal and a skid control means (40) controlled by said skid control instructions for modulating the common brake pressure, having a brake apply valve (51) to supply fluid under pressure to the common supply valve (39), in response to the controller detecting a wheel spin condition of one of said wheels (13, 14), to provide a common brake pressure for both of said brakes and isolating means (42, 43) to isolate the brake (23, 24) associated with the other of said wheels (13, 14) from the brake pressure.