Abstract: A device for controlling skidding on roadway surfaces comprising anti-skid control means for regulating and controlling the braking system of the said vehicles; the said device being automatically responsive to changes in the drag in the said braking system; the said device comprising a first rotatable speed detector wheel mounted on a shaft with at least one permanent magnet embedded therein in the said first wheel, the said first wheel being in combination with a second rotatable wheel which is movably mounted on the said shaft the said second wheel having at least one cam follower for actuating the in and out movement of a coaxial switch plate which is electrically connected to and actuates a release valve in a pneumatic pressure chamber to release the brake chamber pressure therein, the said device being such that it controls the brake chamber pressure so that optimum lineal deceleration is maintained proportionally to the angular deceleration of the wheels respectively and maximum braking traction is mai