A vehicle brake system and method designed to maximize the contributions from a regenerative braking system, yet still provide adequate safety measures that address potential regenerative braking failure. According to one embodiment, the method determines both a requested deceleration from the driver and an actual deceleration experienced by the vehicle, and uses the difference between these two values to calculate a deceleration error that can be integrated over time and compared to an error threshold. If the integrated or accumulated deceleration error surpasses the error threshold, then the method may reduce or disable the regenerative braking system until it can confirm that it is operating properly.