A method and system for discriminating motor vehicle crashes to actuate a safety restraint (10) utilizes an optical vehicle occupant position detector (12) to generate data (22) representative of the position of an occupant relative to fixed structure within the vehicle. The data (22) is subsequently used by a signal processor/discrimination unit (26) as criteria for a parameter based crash discrimination analysis, and for adjusting parameters of the discrimination analysis, such as changing the discrimination threshold values. The occupant position data optimizes the discrimination analysis used in the system (10) due to the system's ability to customize the discrimination analysis in real time to match actual conditions of a vehicle occupant. Occupant position is determined by detecting the relative intensity, or average of scattering angles of a light beam (34) reflectively scattered by the occupant (24). An optical, low threshold safing sensor (40) can further be used to provide system calibration, discrimination of spurious occupant movement, and data representative of vehicle acceleration.