Abstract: An electrically augmented brake control method in which vacuum booster run-out and pedal force are accurately predicted as a function of master cylinder pressure and engine vacuum, thereby eliminating the expense of dedicated sensors for measuring the same. A mathematical model of the vacuum booster is used to estimate the apply chamber pressure and the operator brake pedal force, based on measured values of engine vacuum (or manifold absolute pressure) and master cylinder pressure. The point of vacuum booster runout can be detected as the point at which the estimated apply chamber pressure reaches atmospheric pressure. In a preferred embodiment, a force-balance approach is used to carry out the estimation in an accurate but simple manner that is especially amenable to real-time control in an automotive on-board micro-controller.