Abstract: A road slope estimation system providing road grade information for vehicle automatic parking assist system includes synchronized filters for processing vehicle speed differentiation to obtain vehicle acceleration to be compared with chassis accelerometer signal. Road grade information is extracted based on the comparison of the two signals. The system includes a dynamic compensator module to minimize the chassis accelerometer signal disturbance caused by chassis dynamic response to vehicle motion. The system further includes a predictive filter to obtain the steady-state filter result during the filter transient stage.