A method for determining a coefficient-of-friction, the method including braking a first wheel of a vehicle such that a slip between the first wheel and a roadway is less than a slip between a second wheel of the vehicle and the roadway, and determining a coefficient-of-friction between the first wheel and the roadway based on the behavior of the first wheel during the braking. The method optionally including hazard braking the vehicle.

Disclosed is a brake control apparatus which starts ABS control on the basis of slip ratio speed and which reduces a variation in the slip ratio at the time of start of the ABS control. A brake ECU computes a braking stiffness BS** in a linearly increasing region of a μ-S characteristic, and computes a slip ratio speed reference value dSref**/dt by dividing a changing speed dFxc**/dt of braking force of a wheel by the braking stiffness BS**. The brake ECU computes, as a slip ratio speed threshold, a value ((dSref**/dt)+dSn) by adding a slip ratio speed noise offset value dSn to the slip ratio speed reference value dSref**/dt and starts ABS control when the slip ratio speed dSc**/dt of the wheel exceeds the slip ratio speed threshold.

Disclosed is a brake control apparatus which starts ABS control on the basis of slip ratio speed and which reduces a variation in the slip ratio at the time of start of the ABS control. A brake ECU computes a braking stiffness BS** in a linearly increasing region of a -S characteristic, and computes a slip ratio speed reference value dSref**/dt by dividing a changing speed dFxc**/dt of braking force of a wheel by the braking stiffness BS**. The brake ECU computes, as a slip ratio speed threshold, a value ((dSref**/dt)+dSn) by adding a slip ratio speed noise offset value dSn to the slip ratio speed reference value dSref**/dt and starts ABS control when the slip ratio speed dSc**/dt of the wheel exceeds the slip ratio speed threshold.

A method for determining a coefficient-of-friction, the method including braking a first wheel of a vehicle such that a slip between the first wheel and a roadway is less than a slip between a second wheel of the vehicle and the roadway, and determining a coefficient-of-friction between the first wheel and the roadway based on the behavior of the first wheel during the braking. The method optionally including hazard braking the vehicle.