A method for detecting the onset of drowsiness in an operator of a vehicle or other apparatus. The operator grips a steering wheel or similar control handle, which continuously outputs gripping signals. The method provides for dynamic offset removal to obtain baseline signals, selection of physiologically-significant signals, combining and processing signals to form a proxy signal, analysis of the proxy signals to detect patterns indicative of the onset of drowsiness, and generating alerts as appropriate. The method provides for multiple sliding windows, for dynamic baseline adjustment; and statistical processing to detect physiologically-meaningful patterns indicative of the onset of drowsiness, as distinct from incidental changes in operator gripping through hand position readjustment during normal operation.