A method for operating a vehicle brake system having both frictional and regenerative braking capabilities. According to one embodiment, the method monitors wheel slip at a number of vehicle wheels, evaluates individual wheel slip at a single wheel as well as collective wheel slip involving multiple wheels, compares the wheel slips to one or more speed-based thresholds that are based on vehicle speed, and uses the comparisons to help distinguish between those situations that warrant disengagement of regenerative braking operations and those that do not.