ABS is designed to control each wheel to it's optimal longitudinal tire force bycontrolling wheel slip at each corner of the vehicle. The optimal amount of tire slipvaries with the road surface friction coefficient and with tire design but typicallyfalls within the 10 to 20 percent range. Controlling wheel slip at each corner of thevehicle can be challenging for a ABS system when road surface friction coefficienttransitions occur. The ABS system must quickly detect the change in road surfaceand modify it s pressure control profiles to prevent loss of maneuverability (high tolow friction surface transition) or to prevent loss of vehicle deceleration capability (low to high friction surface transition), sometimes referred to as vehicle sail-on.Brake pressure is controlled at each wheel through the use of a hydraulic modulator.Refer to Figure 2 for an example of a solenoid based hydraulic modulator.